diff options
Diffstat (limited to 'target/linux/generic-2.6/patches-2.6.32/230-union_mounts.patch')
| -rw-r--r-- | target/linux/generic-2.6/patches-2.6.32/230-union_mounts.patch | 5203 |
1 files changed, 0 insertions, 5203 deletions
diff --git a/target/linux/generic-2.6/patches-2.6.32/230-union_mounts.patch b/target/linux/generic-2.6/patches-2.6.32/230-union_mounts.patch deleted file mode 100644 index 23236a07c6..0000000000 --- a/target/linux/generic-2.6/patches-2.6.32/230-union_mounts.patch +++ /dev/null @@ -1,5203 +0,0 @@ ---- /dev/null -+++ b/Documentation/filesystems/union-mounts.txt -@@ -0,0 +1,187 @@ -+VFS based Union Mounts -+---------------------- -+ -+ 1. What are "Union Mounts" -+ 2. The Union Stack -+ 3. Whiteouts, Opaque Directories, and Fallthrus -+ 4. Copy-up -+ 5. Directory Reading -+ 6. Known Problems -+ 7. References -+ -+------------------------------------------------------------------------------- -+ -+1. What are "Union Mounts" -+========================== -+ -+Please note: this is NOT about UnionFS and it is NOT derived work! -+ -+Traditionally the mount operation is opaque, which means that the content of -+the mount point, the directory where the file system is mounted on, is hidden -+by the content of the mounted file system's root directory until the file -+system is unmounted again. Unlike the traditional UNIX mount mechanism, that -+hides the contents of the mount point, a union mount presents a view as if -+both filesystems are merged together. Although only the topmost layer of the -+mount stack can be altered, it appears as if transparent file system mounts -+allow any file to be created, modified or deleted. -+ -+Most people know the concepts and features of union mounts from other -+operating systems like Sun's Translucent Filesystem, Plan9 or BSD. For an -+in-depth review of union mounts and other unioning file systems, see: -+ -+http://lwn.net/Articles/324291/ -+http://lwn.net/Articles/325369/ -+http://lwn.net/Articles/327738/ -+ -+Here are the key features of this implementation: -+- completely VFS based -+- does not change the namespace stacking -+- directory listings have duplicate entries removed in the kernel -+- writable unions: only the topmost file system layer may be writable -+- writable unions: new whiteout filetype handled inside the kernel -+ -+------------------------------------------------------------------------------- -+ -+2. The Union Stack -+================== -+ -+The mounted file systems are organized in the "file system hierarchy" (tree of -+vfsmount structures), which keeps track about the stacking of file systems -+upon each other. The per-directory view on the file system hierarchy is called -+"mount stack" and reflects the order of file systems, which are mounted on a -+specific directory. -+ -+Union mounts present a single unified view of the contents of two or more file -+systems as if they are merged together. Since the information which file -+system objects are part of a unified view is not directly available from the -+file system hierarchy there is a need for a new structure. The file system -+objects, which are part of a unified view are ordered in a so-called "union -+stack". Only directories can be part of a unified view. -+ -+The link between two layers of the union stack is maintained using the -+union_mount structure (#include <linux/union.h>): -+ -+struct union_mount { -+ atomic_t u_count; /* reference count */ -+ struct mutex u_mutex; -+ struct list_head u_unions; /* list head for d_unions */ -+ struct hlist_node u_hash; /* list head for searching */ -+ struct hlist_node u_rhash; /* list head for reverse searching */ -+ -+ struct path u_this; /* this is me */ -+ struct path u_next; /* this is what I overlay */ -+}; -+ -+The union_mount structure holds a reference (dget,mntget) to the next lower -+layer of the union stack. Since a dentry can be part of multiple unions -+(e.g. with bind mounts) they are tied together via the d_unions field of the -+dentry structure. -+ -+All union_mount structures are cached in two hash tables, one for lookups of -+the next lower layer of the union stack and one for reverse lookups of the -+next upper layer of the union stack. The reverse lookup is necessary to -+resolve CWD relative path lookups. For calculation of the hash value, the -+(dentry,vfsmount) pair is used. The u_this field is used for the hash table -+which is used in forward lookups and the u_next field for the reverse lookups. -+ -+During every new mount (or mount propagation), a new union_mount structure is -+allocated. A reference to the mountpoint's vfsmount and dentry is taken and -+stored in the u_next field. In almost the same manner an union_mount -+structure is created during the first time lookup of a directory within a -+union mount point. In this case the lookup proceeds to all lower layers of the -+union. Therefore the complete union stack is constructed during lookups. -+ -+The union_mount structures of a dentry are destroyed when the dentry itself is -+destroyed. Therefore the dentry cache is indirectly driving the union_mount -+cache like this is done for inodes too. Please note that lower layer -+union_mount structures are kept in memory until the topmost dentry is -+destroyed. -+ -+------------------------------------------------------------------------------- -+ -+3. Whiteouts, Opaque Directories, and Fallthrus -+=========================================================== -+ -+The whiteout filetype isn't new. It has been there for quite some time now -+but Linux's VFS hasn't used it yet. With the availability of union mount code -+inside the VFS the whiteout filetype is getting important to support writable -+union mounts. For read-only union mounts, support for whiteouts or -+copy-on-open is not necessary. -+ -+The whiteout filetype has the same function as negative dentries: they -+describe a filename which isn't there. The creation of whiteouts needs -+lowlevel filesystem support. At the time of writing this, there is whiteout -+support for tmpfs, ext2 and ext3 available. The VFS is extended to make the -+whiteout handling transparent to all its users. The whiteouts are not -+visible to user-space. -+ -+What happens when we create a directory that was previously whited-out? We -+don't want the directory entries from underlying filesystems to suddenly appear -+in the newly created directory. So we mark the directory opaque (the file -+system must support storage of the opaque flag). -+ -+Fallthrus are directory entries that override the opaque flag on a directory -+for that specific directory entry name (the lookup "falls through" to the next -+layer of the union mount). Fallthrus are mainly useful for implementing -+readdir(). -+ -+------------------------------------------------------------------------------- -+ -+4. Copy-up -+=========== -+ -+Any write to an object on any layer other than the topmost triggers a copy-up -+of the object to the topmost file system. For regular files, the copy-up -+happens when it is opened in writable mode. -+ -+Directories are copied up on open, regardless of intent to write, to simplify -+copy-up of any object located below it in the namespace. Otherwise we have to -+walk the entire pathname to create intermediate directories whenever we do a -+copy-up. This is the same approach as BSD union mounts and uses a negigible -+amount of disk space. Note that the actual directory entries themselves are -+not copied-up from the lower levels until (a) the directory is written to, or -+(b) the first readdir() of the directory (more on that later). -+ -+Rename across different levels of the union is implemented as a copy-up -+operation for regular files. Rename of directories simply returns EXDEV, the -+same as if we tried to rename across different mounts. Most applications have -+to handle this case anyway. Some applications do not expect EXDEV on -+rename operations within the same directory, but these applications will also -+be broken with bind mounts. -+ -+------------------------------------------------------------------------------- -+ -+5. Directory Reading -+==================== -+ -+readdir() is somewhat difficult to implement in a unioning file system. We must -+eliminate duplicates, apply whiteouts, and start up readdir() where we left -+off, given a single f_pos value. Our solution is to copy up all the directory -+entries to the topmost directory the first time readdir() is called on a -+directory. During this copy-up, we skip duplicates and entries covered by -+whiteouts, and then create fallthru entries for each remaining visible dentry. -+Then we mark the whole directory opaque. From then on, we just use the topmost -+file system's normal readdir() operation. -+ -+------------------------------------------------------------------------------- -+ -+6. Known Problems -+================= -+ -+- copyup() for other filetypes that reg and dir (e.g. for chown() on devices) -+- symlinks are untested -+ -+------------------------------------------------------------------------------- -+ -+7. References -+============= -+ -+[1] http://marc.info/?l=linux-fsdevel&m=96035682927821&w=2 -+[2] http://marc.info/?l=linux-fsdevel&m=117681527820133&w=2 -+[3] http://marc.info/?l=linux-fsdevel&m=117913503200362&w=2 -+[4] http://marc.info/?l=linux-fsdevel&m=118231827024394&w=2 -+ -+Authors: -+Jan Blunck <jblunck@suse.de> -+Bharata B Rao <bharata@linux.vnet.ibm.com> -+Valerie Aurora <vaurora@redhat.com> ---- a/fs/autofs4/autofs_i.h -+++ b/fs/autofs4/autofs_i.h -@@ -130,6 +130,7 @@ struct autofs_sb_info { - int reghost_enabled; - int needs_reghost; - struct super_block *sb; -+ struct vfsmount *mnt; - struct mutex wq_mutex; - spinlock_t fs_lock; - struct autofs_wait_queue *queues; /* Wait queue pointer */ ---- a/fs/autofs4/init.c -+++ b/fs/autofs4/init.c -@@ -17,7 +17,16 @@ - static int autofs_get_sb(struct file_system_type *fs_type, - int flags, const char *dev_name, void *data, struct vfsmount *mnt) - { -- return get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt); -+ struct autofs_sb_info *sbi; -+ int ret; -+ -+ ret = get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt); -+ if (ret) -+ return ret; -+ -+ sbi = autofs4_sbi(mnt->mnt_sb); -+ sbi->mnt = mnt; -+ return 0; - } - - static struct file_system_type autofs_fs_type = { ---- a/fs/autofs4/root.c -+++ b/fs/autofs4/root.c -@@ -179,6 +179,12 @@ static void *autofs4_follow_link(struct - DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d", - dentry, dentry->d_name.len, dentry->d_name.name, oz_mode, - nd->flags); -+ -+ dput(nd->path.dentry); -+ mntput(nd->path.mnt); -+ nd->path.mnt = mntget(sbi->mnt); -+ nd->path.dentry = dget(dentry); -+ - /* - * For an expire of a covered direct or offset mount we need - * to break out of follow_down() at the autofs mount trigger ---- a/fs/compat.c -+++ b/fs/compat.c -@@ -840,6 +840,9 @@ static int compat_fillonedir(void *__buf - struct compat_old_linux_dirent __user *dirent; - compat_ulong_t d_ino; - -+ if (d_type == DT_WHT) -+ return 0; -+ - if (buf->result) - return -EINVAL; - d_ino = ino; -@@ -911,6 +914,9 @@ static int compat_filldir(void *__buf, c - compat_ulong_t d_ino; - int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(compat_long_t)); - -+ if (d_type == DT_WHT) -+ return 0; -+ - buf->error = -EINVAL; /* only used if we fail.. */ - if (reclen > buf->count) - return -EINVAL; -@@ -1000,6 +1006,9 @@ static int compat_filldir64(void * __buf - int reclen = ALIGN(jj + namlen + 1, sizeof(u64)); - u64 off; - -+ if (d_type == DT_WHT) -+ return 0; -+ - buf->error = -EINVAL; /* only used if we fail.. */ - if (reclen > buf->count) - return -EINVAL; ---- a/fs/dcache.c -+++ b/fs/dcache.c -@@ -18,6 +18,7 @@ - #include <linux/string.h> - #include <linux/mm.h> - #include <linux/fs.h> -+#include <linux/union.h> - #include <linux/fsnotify.h> - #include <linux/slab.h> - #include <linux/init.h> -@@ -158,14 +159,19 @@ static void dentry_lru_del_init(struct d - } - - /** -- * d_kill - kill dentry and return parent -+ * __d_kill - kill dentry and return parent - * @dentry: dentry to kill -+ * @list: kill list -+ * @greedy: return parent instead of putting it on the kill list - * - * The dentry must already be unhashed and removed from the LRU. - * -- * If this is the root of the dentry tree, return NULL. -+ * If this is the root of the dentry tree, return NULL. If greedy is zero, we -+ * put the parent of this dentry on the kill list instead. The callers must -+ * make sure that __d_kill_final() is called on all dentries on the kill list. - */ --static struct dentry *d_kill(struct dentry *dentry) -+static struct dentry *__d_kill(struct dentry *dentry, struct list_head *list, -+ int greedy) - __releases(dentry->d_lock) - __releases(dcache_lock) - { -@@ -173,13 +179,78 @@ static struct dentry *d_kill(struct dent - - list_del(&dentry->d_u.d_child); - dentry_stat.nr_dentry--; /* For d_free, below */ -- /*drops the locks, at that point nobody can reach this dentry */ -+ -+ /* -+ * If we are not greedy we just put this on a list for later processing -+ * (follow up to parent, releasing of inode and freeing dentry memory). -+ */ -+ if (!greedy) { -+ list_del_init(&dentry->d_alias); -+ /* at this point nobody can reach this dentry */ -+ list_add(&dentry->d_lru, list); -+ spin_unlock(&dentry->d_lock); -+ spin_unlock(&dcache_lock); -+ __shrink_d_unions(dentry, list); -+ return NULL; -+ } -+ -+ /* drops the locks, at that point nobody can reach this dentry */ - dentry_iput(dentry); -+ /* If the dentry was in an union delete them */ -+ __shrink_d_unions(dentry, list); -+ if (IS_ROOT(dentry)) -+ parent = NULL; -+ else -+ parent = dentry->d_parent; -+ d_free(dentry); -+ return parent; -+} -+ -+void __dput(struct dentry *, struct list_head *, int); -+ -+static void __d_kill_final(struct dentry *dentry, struct list_head *list) -+{ -+ struct dentry *parent; -+ struct inode *inode = dentry->d_inode; -+ -+ if (inode) { -+ dentry->d_inode = NULL; -+ if (!inode->i_nlink) -+ fsnotify_inoderemove(inode); -+ if (dentry->d_op && dentry->d_op->d_iput) -+ dentry->d_op->d_iput(dentry, inode); -+ else -+ iput(inode); -+ } -+ - if (IS_ROOT(dentry)) - parent = NULL; - else - parent = dentry->d_parent; - d_free(dentry); -+ __dput(parent, list, 1); -+} -+ -+/** -+ * d_kill - kill dentry and return parent -+ * @dentry: dentry to kill -+ * -+ * The dentry must already be unhashed and removed from the LRU. -+ * -+ * If this is the root of the dentry tree, return NULL. -+ */ -+static struct dentry *d_kill(struct dentry *dentry) -+{ -+ LIST_HEAD(mortuary); -+ struct dentry *parent; -+ -+ parent = __d_kill(dentry, &mortuary, 1); -+ while (!list_empty(&mortuary)) { -+ dentry = list_entry(mortuary.next, struct dentry, d_lru); -+ list_del(&dentry->d_lru); -+ __d_kill_final(dentry, &mortuary); -+ } -+ - return parent; - } - -@@ -200,19 +271,24 @@ static struct dentry *d_kill(struct dent - * Real recursion would eat up our stack space. - */ - --/* -- * dput - release a dentry -- * @dentry: dentry to release -+/** -+ * __dput - release a dentry -+ * @dentry: dentry to release -+ * @list: kill list argument for __d_kill() -+ * @greedy: greedy argument for __d_kill() - * - * Release a dentry. This will drop the usage count and if appropriate - * call the dentry unlink method as well as removing it from the queues and - * releasing its resources. If the parent dentries were scheduled for release -- * they too may now get deleted. -+ * they too may now get deleted if @greedy is not zero. Otherwise parent is -+ * added to the kill list. The callers must make sure that __d_kill_final() is -+ * called on all dentries on the kill list. -+ * -+ * You probably want to use dput() instead. - * - * no dcache lock, please. - */ -- --void dput(struct dentry *dentry) -+void __dput(struct dentry *dentry, struct list_head *list, int greedy) - { - if (!dentry) - return; -@@ -253,12 +329,35 @@ unhash_it: - kill_it: - /* if dentry was on the d_lru list delete it from there */ - dentry_lru_del(dentry); -- dentry = d_kill(dentry); -+ dentry = __d_kill(dentry, list, greedy); - if (dentry) - goto repeat; - } - - /** -+ * dput - release a dentry -+ * @dentry: dentry to release -+ * -+ * Release a dentry. This will drop the usage count and if appropriate -+ * call the dentry unlink method as well as removing it from the queues and -+ * releasing its resources. If the parent dentries were scheduled for release -+ * they too may now get deleted. -+ * -+ * no dcache lock, please. -+ */ -+void dput(struct dentry *dentry) -+{ -+ LIST_HEAD(mortuary); -+ -+ __dput(dentry, &mortuary, 1); -+ while (!list_empty(&mortuary)) { -+ dentry = list_entry(mortuary.next, struct dentry, d_lru); -+ list_del(&dentry->d_lru); -+ __d_kill_final(dentry, &mortuary); -+ } -+} -+ -+/** - * d_invalidate - invalidate a dentry - * @dentry: dentry to invalidate - * -@@ -690,6 +789,7 @@ static void shrink_dcache_for_umount_sub - iput(inode); - } - -+ shrink_d_unions(dentry); - d_free(dentry); - - /* finished when we fall off the top of the tree, -@@ -952,6 +1052,10 @@ struct dentry *d_alloc(struct dentry * p - INIT_LIST_HEAD(&dentry->d_lru); - INIT_LIST_HEAD(&dentry->d_subdirs); - INIT_LIST_HEAD(&dentry->d_alias); -+#ifdef CONFIG_UNION_MOUNT -+ INIT_LIST_HEAD(&dentry->d_unions); -+ dentry->d_unionized = 0; -+#endif - - if (parent) { - dentry->d_parent = dget(parent); -@@ -982,8 +1086,10 @@ struct dentry *d_alloc_name(struct dentr - /* the caller must hold dcache_lock */ - static void __d_instantiate(struct dentry *dentry, struct inode *inode) - { -- if (inode) -+ if (inode) { -+ dentry->d_flags &= ~(DCACHE_WHITEOUT|DCACHE_FALLTHRU); - list_add(&dentry->d_alias, &inode->i_dentry); -+ } - dentry->d_inode = inode; - fsnotify_d_instantiate(dentry, inode); - } -@@ -1514,7 +1620,9 @@ void d_delete(struct dentry * dentry) - spin_lock(&dentry->d_lock); - isdir = S_ISDIR(dentry->d_inode->i_mode); - if (atomic_read(&dentry->d_count) == 1) { -+ __d_drop_unions(dentry); - dentry_iput(dentry); -+ shrink_d_unions(dentry); - fsnotify_nameremove(dentry, isdir); - return; - } -@@ -1525,14 +1633,14 @@ void d_delete(struct dentry * dentry) - spin_unlock(&dentry->d_lock); - spin_unlock(&dcache_lock); - -+ shrink_d_unions(dentry); - fsnotify_nameremove(dentry, isdir); - } - - static void __d_rehash(struct dentry * entry, struct hlist_head *list) - { -- -- entry->d_flags &= ~DCACHE_UNHASHED; -- hlist_add_head_rcu(&entry->d_hash, list); -+ entry->d_flags &= ~DCACHE_UNHASHED; -+ hlist_add_head_rcu(&entry->d_hash, list); - } - - static void _d_rehash(struct dentry * entry) -@@ -1551,6 +1659,7 @@ void d_rehash(struct dentry * entry) - { - spin_lock(&dcache_lock); - spin_lock(&entry->d_lock); -+ BUG_ON(!d_unhashed(entry)); - _d_rehash(entry); - spin_unlock(&entry->d_lock); - spin_unlock(&dcache_lock); -@@ -2183,7 +2292,9 @@ resume: - struct list_head *tmp = next; - struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); - next = tmp->next; -- if (d_unhashed(dentry)||!dentry->d_inode) -+ if (d_unhashed(dentry)||(!dentry->d_inode && -+ !d_is_whiteout(dentry) && -+ !d_is_fallthru(dentry))) - continue; - if (!list_empty(&dentry->d_subdirs)) { - this_parent = dentry; ---- a/fs/ext2/dir.c -+++ b/fs/ext2/dir.c -@@ -219,7 +219,8 @@ static inline int ext2_match (int len, c - { - if (len != de->name_len) - return 0; -- if (!de->inode) -+ if (!de->inode && ((de->file_type != EXT2_FT_WHT) && -+ (de->file_type != EXT2_FT_FALLTHRU))) - return 0; - return !memcmp(name, de->name, len); - } -@@ -255,6 +256,8 @@ static unsigned char ext2_filetype_table - [EXT2_FT_FIFO] = DT_FIFO, - [EXT2_FT_SOCK] = DT_SOCK, - [EXT2_FT_SYMLINK] = DT_LNK, -+ [EXT2_FT_WHT] = DT_WHT, -+ [EXT2_FT_FALLTHRU] = DT_UNKNOWN, - }; - - #define S_SHIFT 12 -@@ -341,6 +344,18 @@ ext2_readdir (struct file * filp, void * - ext2_put_page(page); - return 0; - } -+ } else if (de->file_type == EXT2_FT_FALLTHRU) { -+ int over; -+ unsigned char d_type = DT_UNKNOWN; -+ -+ offset = (char *)de - kaddr; -+ over = filldir(dirent, de->name, de->name_len, -+ (n<<PAGE_CACHE_SHIFT) | offset, -+ 123, d_type); -+ if (over) { -+ ext2_put_page(page); -+ return 0; -+ } - } - filp->f_pos += ext2_rec_len_from_disk(de->rec_len); - } -@@ -448,6 +463,30 @@ ino_t ext2_inode_by_name(struct inode *d - return res; - } - -+/* Special version for filetype based whiteout support */ -+ino_t ext2_inode_by_dentry(struct inode *dir, struct dentry *dentry) -+{ -+ ino_t res = 0; -+ struct ext2_dir_entry_2 *de; -+ struct page *page; -+ -+ de = ext2_find_entry (dir, &dentry->d_name, &page); -+ if (de) { -+ res = le32_to_cpu(de->inode); -+ if (!res && de->file_type == EXT2_FT_WHT) { -+ spin_lock(&dentry->d_lock); -+ dentry->d_flags |= DCACHE_WHITEOUT; -+ spin_unlock(&dentry->d_lock); -+ } else if(!res && de->file_type == EXT2_FT_FALLTHRU) { -+ spin_lock(&dentry->d_lock); -+ dentry->d_flags |= DCACHE_FALLTHRU; -+ spin_unlock(&dentry->d_lock); -+ } -+ ext2_put_page(page); -+ } -+ return res; -+} -+ - /* Releases the page */ - void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de, - struct page *page, struct inode *inode, int update_times) -@@ -472,9 +511,10 @@ void ext2_set_link(struct inode *dir, st - } - - /* -- * Parent is locked. -+ * Find or append a given dentry to the parent directory - */ --int ext2_add_link (struct dentry *dentry, struct inode *inode) -+static ext2_dirent * ext2_append_entry(struct dentry * dentry, -+ struct page ** page) - { - struct inode *dir = dentry->d_parent->d_inode; - const char *name = dentry->d_name.name; -@@ -482,13 +522,10 @@ int ext2_add_link (struct dentry *dentry - unsigned chunk_size = ext2_chunk_size(dir); - unsigned reclen = EXT2_DIR_REC_LEN(namelen); - unsigned short rec_len, name_len; -- struct page *page = NULL; -- ext2_dirent * de; -+ ext2_dirent * de = NULL; - unsigned long npages = dir_pages(dir); - unsigned long n; - char *kaddr; -- loff_t pos; -- int err; - - /* - * We take care of directory expansion in the same loop. -@@ -498,55 +535,97 @@ int ext2_add_link (struct dentry *dentry - for (n = 0; n <= npages; n++) { - char *dir_end; - -- page = ext2_get_page(dir, n, 0); -- err = PTR_ERR(page); -- if (IS_ERR(page)) -+ *page = ext2_get_page(dir, n, 0); -+ de = ERR_PTR(PTR_ERR(*page)); -+ if (IS_ERR(*page)) - goto out; -- lock_page(page); -- kaddr = page_address(page); -+ lock_page(*page); -+ kaddr = page_address(*page); - dir_end = kaddr + ext2_last_byte(dir, n); - de = (ext2_dirent *)kaddr; - kaddr += PAGE_CACHE_SIZE - reclen; - while ((char *)de <= kaddr) { - if ((char *)de == dir_end) { - /* We hit i_size */ -- name_len = 0; -- rec_len = chunk_size; -+ de->name_len = 0; - de->rec_len = ext2_rec_len_to_disk(chunk_size); - de->inode = 0; -+ de->file_type = 0; - goto got_it; - } - if (de->rec_len == 0) { - ext2_error(dir->i_sb, __func__, - "zero-length directory entry"); -- err = -EIO; -+ de = ERR_PTR(-EIO); - goto out_unlock; - } -- err = -EEXIST; - if (ext2_match (namelen, name, de)) -- goto out_unlock; -+ goto got_it; - name_len = EXT2_DIR_REC_LEN(de->name_len); - rec_len = ext2_rec_len_from_disk(de->rec_len); -- if (!de->inode && rec_len >= reclen) -+ if (!de->inode && (de->file_type != EXT2_FT_WHT) && -+ (de->file_type != EXT2_FT_FALLTHRU) && -+ (rec_len >= reclen)) - goto got_it; - if (rec_len >= name_len + reclen) - goto got_it; - de = (ext2_dirent *) ((char *) de + rec_len); - } -- unlock_page(page); -- ext2_put_page(page); -+ unlock_page(*page); -+ ext2_put_page(*page); - } -+ - BUG(); -- return -EINVAL; - - got_it: -+ return de; -+ /* OFFSET_CACHE */ -+out_unlock: -+ unlock_page(*page); -+ ext2_put_page(*page); -+out: -+ return de; -+} -+ -+/* -+ * Parent is locked. -+ */ -+int ext2_add_link (struct dentry *dentry, struct inode *inode) -+{ -+ struct inode *dir = dentry->d_parent->d_inode; -+ const char *name = dentry->d_name.name; -+ int namelen = dentry->d_name.len; -+ unsigned short rec_len, name_len; -+ ext2_dirent * de; -+ struct page *page; -+ loff_t pos; -+ int err; -+ -+ de = ext2_append_entry(dentry, &page); -+ if (IS_ERR(de)) -+ return PTR_ERR(de); -+ -+ err = -EEXIST; -+ if (ext2_match (namelen, name, de)) { -+ if ((de->file_type == EXT2_FT_WHT) || -+ (de->file_type == EXT2_FT_FALLTHRU)) -+ goto got_it; -+ goto out_unlock; -+ } -+ -+got_it: -+ name_len = EXT2_DIR_REC_LEN(de->name_len); -+ rec_len = ext2_rec_len_from_disk(de->rec_len); -+ - pos = page_offset(page) + - (char*)de - (char*)page_address(page); - err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0, - &page, NULL); - if (err) - goto out_unlock; -- if (de->inode) { -+ if (de->inode || (((de->file_type == EXT2_FT_WHT) || -+ (de->file_type == EXT2_FT_FALLTHRU)) && -+ !ext2_match (namelen, name, de))) { - ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len); - de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len); - de->rec_len = ext2_rec_len_to_disk(name_len); -@@ -563,7 +642,60 @@ got_it: - /* OFFSET_CACHE */ - out_put: - ext2_put_page(page); --out: -+ return err; -+out_unlock: -+ unlock_page(page); -+ goto out_put; -+} -+ -+/* -+ * Create a fallthru entry. -+ */ -+int ext2_fallthru_entry (struct inode *dir, struct dentry *dentry) -+{ -+ const char *name = dentry->d_name.name; -+ int namelen = dentry->d_name.len; -+ unsigned short rec_len, name_len; -+ ext2_dirent * de; -+ struct page *page; -+ loff_t pos; -+ int err; -+ -+ de = ext2_append_entry(dentry, &page); -+ if (IS_ERR(de)) -+ return PTR_ERR(de); -+ -+ err = -EEXIST; -+ if (ext2_match (namelen, name, de)) -+ goto out_unlock; -+ -+ name_len = EXT2_DIR_REC_LEN(de->name_len); -+ rec_len = ext2_rec_len_from_disk(de->rec_len); -+ -+ pos = page_offset(page) + -+ (char*)de - (char*)page_address(page); -+ err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0, -+ &page, NULL); -+ if (err) -+ goto out_unlock; -+ if (de->inode || (de->file_type == EXT2_FT_WHT) || -+ (de->file_type == EXT2_FT_FALLTHRU)) { -+ ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len); -+ de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len); -+ de->rec_len = ext2_rec_len_to_disk(name_len); -+ de = de1; -+ } -+ de->name_len = namelen; -+ memcpy(de->name, name, namelen); -+ de->inode = 0; -+ de->file_type = EXT2_FT_FALLTHRU; -+ err = ext2_commit_chunk(page, pos, rec_len); -+ dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC; -+ EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL; -+ mark_inode_dirty(dir); -+ /* OFFSET_CACHE */ -+out_put: -+ ext2_put_page(page); - return err; - out_unlock: - unlock_page(page); -@@ -616,6 +748,70 @@ out: - return err; - } - -+int ext2_whiteout_entry (struct inode * dir, struct dentry * dentry, -+ struct ext2_dir_entry_2 * de, struct page * page) -+{ -+ const char *name = dentry->d_name.name; -+ int namelen = dentry->d_name.len; -+ unsigned short rec_len, name_len; -+ loff_t pos; -+ int err; -+ -+ if (!de) { -+ de = ext2_append_entry(dentry, &page); -+ BUG_ON(!de); -+ } -+ -+ err = -EEXIST; -+ if (ext2_match (namelen, name, de) && -+ (de->file_type == EXT2_FT_WHT)) { -+ ext2_error(dir->i_sb, __func__, -+ "entry is already a whiteout in directory #%lu", -+ dir->i_ino); -+ goto out_unlock; -+ } -+ -+ name_len = EXT2_DIR_REC_LEN(de->name_len); -+ rec_len = ext2_rec_len_from_disk(de->rec_len); -+ -+ pos = page_offset(page) + -+ (char*)de - (char*)page_address(page); -+ err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0, -+ &page, NULL); -+ if (err) -+ goto out_unlock; -+ /* -+ * We whiteout an existing entry. Do what ext2_delete_entry() would do, -+ * except that we don't need to merge with the previous entry since -+ * we are going to reuse it. -+ */ -+ if (ext2_match (namelen, name, de)) -+ de->inode = 0; -+ if (de->inode || (((de->file_type == EXT2_FT_WHT) || -+ (de->file_type == EXT2_FT_FALLTHRU)) && -+ !ext2_match (namelen, name, de))) { -+ ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len); -+ de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len); -+ de->rec_len = ext2_rec_len_to_disk(name_len); -+ de = de1; -+ } -+ de->name_len = namelen; -+ memcpy(de->name, name, namelen); -+ de->inode = 0; -+ de->file_type = EXT2_FT_WHT; -+ err = ext2_commit_chunk(page, pos, rec_len); -+ dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC; -+ EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL; -+ mark_inode_dirty(dir); -+ /* OFFSET_CACHE */ -+out_put: -+ ext2_put_page(page); -+ return err; -+out_unlock: -+ unlock_page(page); -+ goto out_put; -+} -+ - /* - * Set the first fragment of directory. - */ ---- a/fs/ext2/ext2.h -+++ b/fs/ext2/ext2.h -@@ -102,9 +102,13 @@ extern void ext2_rsv_window_add(struct s - /* dir.c */ - extern int ext2_add_link (struct dentry *, struct inode *); - extern ino_t ext2_inode_by_name(struct inode *, struct qstr *); -+extern ino_t ext2_inode_by_dentry(struct inode *, struct dentry *); - extern int ext2_make_empty(struct inode *, struct inode *); - extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,struct qstr *, struct page **); - extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *); -+extern int ext2_whiteout_entry (struct inode *, struct dentry *, -+ struct ext2_dir_entry_2 *, struct page *); -+extern int ext2_fallthru_entry (struct inode *, struct dentry *); - extern int ext2_empty_dir (struct inode *); - extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **); - extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int); ---- a/fs/ext2/inode.c -+++ b/fs/ext2/inode.c -@@ -1178,7 +1178,8 @@ void ext2_set_inode_flags(struct inode * - { - unsigned int flags = EXT2_I(inode)->i_flags; - -- inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC); -+ inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC| -+ S_OPAQUE); - if (flags & EXT2_SYNC_FL) - inode->i_flags |= S_SYNC; - if (flags & EXT2_APPEND_FL) -@@ -1189,6 +1190,8 @@ void ext2_set_inode_flags(struct inode * - inode->i_flags |= S_NOATIME; - if (flags & EXT2_DIRSYNC_FL) - inode->i_flags |= S_DIRSYNC; -+ if (flags & EXT2_OPAQUE_FL) -+ inode->i_flags |= S_OPAQUE; - } - - /* Propagate flags from i_flags to EXT2_I(inode)->i_flags */ -@@ -1196,8 +1199,8 @@ void ext2_get_inode_flags(struct ext2_in - { - unsigned int flags = ei->vfs_inode.i_flags; - -- ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL| -- EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL); -+ ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|EXT2_IMMUTABLE_FL| -+ EXT2_NOATIME_FL|EXT2_DIRSYNC_FL|EXT2_OPAQUE_FL); - if (flags & S_SYNC) - ei->i_flags |= EXT2_SYNC_FL; - if (flags & S_APPEND) -@@ -1208,6 +1211,8 @@ void ext2_get_inode_flags(struct ext2_in - ei->i_flags |= EXT2_NOATIME_FL; - if (flags & S_DIRSYNC) - ei->i_flags |= EXT2_DIRSYNC_FL; -+ if (flags & S_OPAQUE) -+ ei->i_flags |= EXT2_OPAQUE_FL; - } - - struct inode *ext2_iget (struct super_block *sb, unsigned long ino) ---- a/fs/ext2/namei.c -+++ b/fs/ext2/namei.c -@@ -54,15 +54,16 @@ static inline int ext2_add_nondir(struct - * Methods themselves. - */ - --static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd) -+static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, -+ struct nameidata *nd) - { - struct inode * inode; - ino_t ino; -- -+ - if (dentry->d_name.len > EXT2_NAME_LEN) - return ERR_PTR(-ENAMETOOLONG); - -- ino = ext2_inode_by_name(dir, &dentry->d_name); -+ ino = ext2_inode_by_dentry(dir, dentry); - inode = NULL; - if (ino) { - inode = ext2_iget(dir->i_sb, ino); -@@ -230,6 +231,10 @@ static int ext2_mkdir(struct inode * dir - else - inode->i_mapping->a_ops = &ext2_aops; - -+ /* if we call mkdir on a whiteout create an opaque directory */ -+ if (dentry->d_flags & DCACHE_WHITEOUT) -+ inode->i_flags |= S_OPAQUE; -+ - inode_inc_link_count(inode); - - err = ext2_make_empty(inode, dir); -@@ -293,6 +298,78 @@ static int ext2_rmdir (struct inode * di - return err; - } - -+/* -+ * Create a whiteout for the dentry -+ */ -+static int ext2_whiteout(struct inode *dir, struct dentry *dentry, -+ struct dentry *new_dentry) -+{ -+ struct inode * inode = dentry->d_inode; -+ struct ext2_dir_entry_2 * de = NULL; -+ struct page * page; -+ int err = -ENOTEMPTY; -+ -+ if (!EXT2_HAS_INCOMPAT_FEATURE(dir->i_sb, -+ EXT2_FEATURE_INCOMPAT_FILETYPE)) { -+ ext2_error (dir->i_sb, "ext2_whiteout", -+ "can't set whiteout filetype"); -+ err = -EPERM; -+ goto out; -+ } -+ -+ if (inode) { -+ if (S_ISDIR(inode->i_mode) && !ext2_empty_dir(inode)) -+ goto out; -+ -+ err = -ENOENT; -+ de = ext2_find_entry (dir, &dentry->d_name, &page); -+ if (!de) -+ goto out; -+ lock_page(page); -+ } -+ -+ err = ext2_whiteout_entry (dir, dentry, de, page); -+ if (err) -+ goto out; -+ -+ spin_lock(&new_dentry->d_lock); -+ new_dentry->d_flags &= ~DCACHE_FALLTHRU; -+ new_dentry->d_flags |= DCACHE_WHITEOUT; -+ spin_unlock(&new_dentry->d_lock); -+ d_add(new_dentry, NULL); -+ -+ if (inode) { -+ inode->i_ctime = dir->i_ctime; -+ inode_dec_link_count(inode); -+ if (S_ISDIR(inode->i_mode)) { -+ inode->i_size = 0; -+ inode_dec_link_count(inode); -+ inode_dec_link_count(dir); -+ } -+ } -+ err = 0; -+out: -+ return err; -+} -+ -+/* -+ * Create a fallthru entry. -+ */ -+static int ext2_fallthru (struct inode *dir, struct dentry *dentry) -+{ -+ int err; -+ -+ err = ext2_fallthru_entry(dir, dentry); -+ if (err) -+ return err; -+ -+ d_instantiate(dentry, NULL); -+ spin_lock(&dentry->d_lock); -+ dentry->d_flags |= DCACHE_FALLTHRU; -+ spin_unlock(&dentry->d_lock); -+ return 0; -+} -+ - static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry, - struct inode * new_dir, struct dentry * new_dentry ) - { -@@ -392,6 +469,8 @@ const struct inode_operations ext2_dir_i - .mkdir = ext2_mkdir, - .rmdir = ext2_rmdir, - .mknod = ext2_mknod, -+ .whiteout = ext2_whiteout, -+ .fallthru = ext2_fallthru, - .rename = ext2_rename, - #ifdef CONFIG_EXT2_FS_XATTR - .setxattr = generic_setxattr, ---- a/fs/ext2/super.c -+++ b/fs/ext2/super.c -@@ -1062,6 +1062,13 @@ static int ext2_fill_super(struct super_ - if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL)) - ext2_warning(sb, __func__, - "mounting ext3 filesystem as ext2"); -+ -+ /* -+ * Whiteouts (and fallthrus) require explicit whiteout support. -+ */ -+ if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_WHITEOUT)) -+ sb->s_flags |= MS_WHITEOUT; -+ - ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY); - return 0; - ---- a/fs/Kconfig -+++ b/fs/Kconfig -@@ -59,6 +59,14 @@ source "fs/notify/Kconfig" - - source "fs/quota/Kconfig" - -+config UNION_MOUNT -+ bool "Union mount support (EXPERIMENTAL)" -+ depends on EXPERIMENTAL -+ ---help--- -+ If you say Y here, you will be able to mount file systems as -+ union mount stacks. This is a VFS based implementation and -+ should work with all file systems. If unsure, say N. -+ - source "fs/autofs/Kconfig" - source "fs/autofs4/Kconfig" - source "fs/fuse/Kconfig" ---- a/fs/libfs.c -+++ b/fs/libfs.c -@@ -133,6 +133,7 @@ int dcache_readdir(struct file * filp, v - struct dentry *cursor = filp->private_data; - struct list_head *p, *q = &cursor->d_u.d_child; - ino_t ino; -+ int d_type; - int i = filp->f_pos; - - switch (i) { -@@ -158,14 +159,25 @@ int dcache_readdir(struct file * filp, v - for (p=q->next; p != &dentry->d_subdirs; p=p->next) { - struct dentry *next; - next = list_entry(p, struct dentry, d_u.d_child); -- if (d_unhashed(next) || !next->d_inode) -+ if (d_unhashed(next) || (!next->d_inode && !d_is_fallthru(next))) - continue; - -+ if (d_is_fallthru(next)) { -+ /* XXX Make up things we can -+ * only get out of the inode. -+ * Should probably really do a -+ * lookup instead. */ -+ ino = 100; /* XXX Made up number of no significance */ -+ d_type = DT_UNKNOWN; -+ } else { -+ ino = next->d_inode->i_ino; -+ d_type = dt_type(next->d_inode); -+ } -+ - spin_unlock(&dcache_lock); - if (filldir(dirent, next->d_name.name, - next->d_name.len, filp->f_pos, -- next->d_inode->i_ino, -- dt_type(next->d_inode)) < 0) -+ ino, d_type) < 0) - return 0; - spin_lock(&dcache_lock); - /* next is still alive */ ---- a/fs/Makefile -+++ b/fs/Makefile -@@ -52,6 +52,7 @@ obj-$(CONFIG_NFS_COMMON) += nfs_common/ - obj-$(CONFIG_GENERIC_ACL) += generic_acl.o - - obj-y += quota/ -+obj-$(CONFIG_UNION_MOUNT) += union.o - - obj-$(CONFIG_PROC_FS) += proc/ - obj-y += partitions/ ---- a/fs/namei.c -+++ b/fs/namei.c -@@ -33,6 +33,7 @@ - #include <linux/fcntl.h> - #include <linux/device_cgroup.h> - #include <linux/fs_struct.h> -+#include <linux/union.h> - #include <asm/uaccess.h> - - #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE]) -@@ -242,16 +243,17 @@ int generic_permission(struct inode *ino - } - - /** -- * inode_permission - check for access rights to a given inode -+ * __inode_permission - check for access rights to a given inode - * @inode: inode to check permission on - * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) -+ * @rofs: check for read-only fs - * - * Used to check for read/write/execute permissions on an inode. - * We use "fsuid" for this, letting us set arbitrary permissions - * for filesystem access without changing the "normal" uids which - * are used for other things. - */ --int inode_permission(struct inode *inode, int mask) -+int __inode_permission(struct inode *inode, int mask, int rofs) - { - int retval; - -@@ -261,7 +263,7 @@ int inode_permission(struct inode *inode - /* - * Nobody gets write access to a read-only fs. - */ -- if (IS_RDONLY(inode) && -+ if ((rofs & IS_RDONLY(inode)) && - (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) - return -EROFS; - -@@ -289,6 +291,18 @@ int inode_permission(struct inode *inode - } - - /** -+ * inode_permission - check for access rights to a given inode -+ * @inode: inode to check permission on -+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) -+ * -+ * This version pays attention to the MS_RDONLY flag on the fs. -+ */ -+int inode_permission(struct inode *inode, int mask) -+{ -+ return __inode_permission(inode, mask, 1); -+} -+ -+/** - * file_permission - check for additional access rights to a given file - * @file: file to check access rights for - * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) -@@ -417,15 +431,10 @@ do_revalidate(struct dentry *dentry, str - * Internal lookup() using the new generic dcache. - * SMP-safe - */ --static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd) -+static struct dentry *cache_lookup(struct dentry *parent, struct qstr *name, -+ struct nameidata *nd) - { -- struct dentry * dentry = __d_lookup(parent, name); -- -- /* lockess __d_lookup may fail due to concurrent d_move() -- * in some unrelated directory, so try with d_lookup -- */ -- if (!dentry) -- dentry = d_lookup(parent, name); -+ struct dentry *dentry = d_lookup(parent, name); - - if (dentry && dentry->d_op && dentry->d_op->d_revalidate) - dentry = do_revalidate(dentry, nd); -@@ -434,6 +443,208 @@ static struct dentry * cached_lookup(str - } - - /* -+ * Theory of operation for opaque, whiteout, and fallthru: -+ * -+ * whiteout: Unconditionally stop lookup here - ENOENT -+ * -+ * opaque: Don't lookup in directories lower in the union stack -+ * -+ * fallthru: While looking up an entry, ignore the opaque flag for the -+ * current directory only. -+ * -+ * A union stack is a linked list of directory dentries which appear -+ * in the same place in the namespace. When constructing the union -+ * stack, we include directories below opaque directories so that we -+ * can properly handle fallthrus. All non-fallthru lookups have to -+ * check for the opaque flag on the parent directory and obey it. -+ * -+ * In general, the code pattern is to lookup the the topmost entry -+ * first (either the first visible non-negative dentry or a negative -+ * dentry in the topmost layer of the union), then build the union -+ * stack for the newly looked-up entry (if it is a directory). -+ */ -+ -+/** -+ * __cache_lookup_topmost - lookup the topmost (non-)negative dentry -+ * -+ * @nd - parent's nameidata -+ * @name - pathname part to lookup -+ * @path - found dentry for pathname part -+ * -+ * This is used for union mount lookups from dcache. The first non-negative -+ * dentry is searched on all layers of the union stack. Otherwise the topmost -+ * negative dentry is returned. -+ */ -+static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct dentry *dentry; -+ -+ dentry = d_lookup(nd->path.dentry, name); -+ if (dentry && dentry->d_op && dentry->d_op->d_revalidate) -+ dentry = do_revalidate(dentry, nd); -+ -+ /* -+ * Remember the topmost negative dentry in case we don't find anything -+ */ -+ path->dentry = dentry; -+ path->mnt = dentry ? nd->path.mnt : NULL; -+ -+ if (!dentry || (dentry->d_inode || d_is_whiteout(dentry))) -+ return !dentry; -+ -+ /* Keep going through opaque directories if we found a fallthru */ -+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry)) -+ return !dentry; -+ -+ /* look for the first non-negative or whiteout dentry */ -+ -+ while (follow_union_down(&nd->path)) { -+ dentry = d_hash_and_lookup(nd->path.dentry, name); -+ -+ /* -+ * If parts of the union stack are not in the dcache we need -+ * to do a real lookup -+ */ -+ if (!dentry) -+ goto out_dput; -+ -+ /* -+ * If parts of the union don't survive the revalidation we -+ * need to do a real lookup -+ */ -+ if (dentry->d_op && dentry->d_op->d_revalidate) { -+ dentry = do_revalidate(dentry, nd); -+ if (!dentry) -+ goto out_dput; -+ } -+ -+ if (dentry->d_inode || d_is_whiteout(dentry)) -+ goto out_dput; -+ -+ /* Stop the lookup on opaque parent and non-fallthru child */ -+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry)) -+ goto out_dput; -+ -+ dput(dentry); -+ } -+ -+ return !dentry; -+ -+out_dput: -+ dput(path->dentry); -+ path->dentry = dentry; -+ path->mnt = dentry ? mntget(nd->path.mnt) : NULL; -+ return !dentry; -+} -+ -+/** -+ * __cache_lookup_build_union - build the union stack for this part, -+ * cached version -+ * -+ * This is called after you have the topmost dentry in @path. -+ */ -+static int __cache_lookup_build_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path last = *path; -+ struct dentry *dentry; -+ -+ while (follow_union_down(&nd->path)) { -+ dentry = d_hash_and_lookup(nd->path.dentry, name); -+ if (!dentry) -+ return 1; -+ -+ if (dentry->d_op && dentry->d_op->d_revalidate) { -+ dentry = do_revalidate(dentry, nd); -+ if (!dentry) -+ return 1; -+ } -+ -+ if (d_is_whiteout(dentry)) { -+ dput(dentry); -+ break; -+ } -+ -+ if (!dentry->d_inode) { -+ dput(dentry); -+ continue; -+ } -+ -+ /* only directories can be part of a union stack */ -+ if (!S_ISDIR(dentry->d_inode->i_mode)) { -+ dput(dentry); -+ break; -+ } -+ -+ /* Add the newly discovered dir to the union stack */ -+ append_to_union(last.mnt, last.dentry, nd->path.mnt, dentry); -+ -+ if (last.dentry != path->dentry) -+ path_put(&last); -+ last.dentry = dentry; -+ last.mnt = mntget(nd->path.mnt); -+ } -+ -+ if (last.dentry != path->dentry) -+ path_put(&last); -+ -+ return 0; -+} -+ -+/** -+ * cache_lookup_union - lookup a single pathname part from dcache -+ * -+ * This is a union mount capable version of what d_lookup() & revalidate() -+ * would do. This function returns a valid (union) dentry on success. -+ * -+ * Remember: On failure it means that parts of the union aren't cached. You -+ * should call real_lookup() afterwards to find the proper (union) dentry. -+ */ -+static int cache_lookup_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ int res ; -+ -+ if (!IS_MNT_UNION(nd->path.mnt)) { -+ path->dentry = cache_lookup(nd->path.dentry, name, nd); -+ path->mnt = path->dentry ? nd->path.mnt : NULL; -+ res = path->dentry ? 0 : 1; -+ } else { -+ struct path safe = { -+ .dentry = nd->path.dentry, -+ .mnt = nd->path.mnt -+ }; -+ -+ path_get(&safe); -+ res = __cache_lookup_topmost(nd, name, path); -+ if (res) -+ goto out; -+ -+ /* only directories can be part of a union stack */ -+ if (!path->dentry->d_inode || -+ !S_ISDIR(path->dentry->d_inode->i_mode)) -+ goto out; -+ -+ /* Build the union stack for this part */ -+ res = __cache_lookup_build_union(nd, name, path); -+ if (res) { -+ dput(path->dentry); -+ if (path->mnt != safe.mnt) -+ mntput(path->mnt); -+ goto out; -+ } -+ -+out: -+ path_put(&nd->path); -+ nd->path.dentry = safe.dentry; -+ nd->path.mnt = safe.mnt; -+ } -+ -+ return res; -+} -+ -+/* - * Short-cut version of permission(), for calling by - * path_walk(), when dcache lock is held. Combines parts - * of permission() and generic_permission(), and tests ONLY for -@@ -473,10 +684,11 @@ ok: - * make sure that nobody added the entry to the dcache in the meantime.. - * SMP-safe - */ --static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd) -+static int real_lookup(struct nameidata *nd, struct qstr *name, -+ struct path *path) - { -- struct dentry * result; -- struct inode *dir = parent->d_inode; -+ struct inode *dir = nd->path.dentry->d_inode; -+ int res = 0; - - mutex_lock(&dir->i_mutex); - /* -@@ -493,27 +705,36 @@ static struct dentry * real_lookup(struc - * - * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup - */ -- result = d_lookup(parent, name); -- if (!result) { -+ path->dentry = d_lookup(nd->path.dentry, name); -+ path->mnt = nd->path.mnt; -+ if (!path->dentry) { - struct dentry *dentry; - - /* Don't create child dentry for a dead directory. */ -- result = ERR_PTR(-ENOENT); -- if (IS_DEADDIR(dir)) -+ if (IS_DEADDIR(dir)) { -+ res = -ENOENT; - goto out_unlock; -+ } - -- dentry = d_alloc(parent, name); -- result = ERR_PTR(-ENOMEM); -+ dentry = d_alloc(nd->path.dentry, name); - if (dentry) { -- result = dir->i_op->lookup(dir, dentry, nd); -- if (result) -+ path->dentry = dir->i_op->lookup(dir, dentry, nd); -+ if (path->dentry) { - dput(dentry); -- else -- result = dentry; -+ if (IS_ERR(path->dentry)) { -+ res = PTR_ERR(path->dentry); -+ path->dentry = NULL; -+ path->mnt = NULL; -+ } -+ } else -+ path->dentry = dentry; -+ } else { -+ res = -ENOMEM; -+ path->mnt = NULL; - } - out_unlock: - mutex_unlock(&dir->i_mutex); -- return result; -+ return res; - } - - /* -@@ -521,12 +742,170 @@ out_unlock: - * we waited on the semaphore. Need to revalidate. - */ - mutex_unlock(&dir->i_mutex); -- if (result->d_op && result->d_op->d_revalidate) { -- result = do_revalidate(result, nd); -- if (!result) -- result = ERR_PTR(-ENOENT); -+ if (path->dentry->d_op && path->dentry->d_op->d_revalidate) { -+ path->dentry = do_revalidate(path->dentry, nd); -+ if (!path->dentry) { -+ res = -ENOENT; -+ path->mnt = NULL; -+ } -+ if (IS_ERR(path->dentry)) { -+ res = PTR_ERR(path->dentry); -+ path->dentry = NULL; -+ path->mnt = NULL; -+ } - } -- return result; -+ -+ return res; -+} -+ -+/** -+ * __real_lookup_topmost - lookup topmost dentry, non-cached version -+ * -+ * If we reach a dentry with restricted access, we just stop the lookup -+ * because we shouldn't see through that dentry. Same thing for dentry -+ * type mismatch and whiteouts. -+ * -+ * FIXME: -+ * - handle union stacks in use -+ * - handle union stacks mounted upon union stacks -+ * - avoid unnecessary allocations of union locks -+ */ -+static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path next; -+ int err; -+ -+ err = real_lookup(nd, name, path); -+ if (err) -+ return err; -+ -+ if (path->dentry->d_inode || d_is_whiteout(path->dentry)) -+ return 0; -+ -+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry)) -+ return 0; -+ -+ while (follow_union_down(&nd->path)) { -+ name->hash = full_name_hash(name->name, name->len); -+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) { -+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry, -+ name); -+ if (err < 0) -+ goto out; -+ } -+ -+ err = real_lookup(nd, name, &next); -+ if (err) -+ goto out; -+ -+ if (next.dentry->d_inode || d_is_whiteout(next.dentry)) { -+ dput(path->dentry); -+ mntget(next.mnt); -+ *path = next; -+ goto out; -+ } -+ -+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry)) -+ goto out; -+ -+ dput(next.dentry); -+ } -+out: -+ if (err) -+ dput(path->dentry); -+ return err; -+} -+ -+/** -+ * __real_lookup_build_union: build the union stack for this pathname -+ * part, non-cached version -+ * -+ * Called when not all parts of the union stack are in cache -+ */ -+ -+static int __real_lookup_build_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path last = *path; -+ struct path next; -+ int err = 0; -+ -+ while (follow_union_down(&nd->path)) { -+ /* We need to recompute the hash for lower layer lookups */ -+ name->hash = full_name_hash(name->name, name->len); -+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) { -+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry, -+ name); -+ if (err < 0) -+ goto out; -+ } -+ -+ err = real_lookup(nd, name, &next); -+ if (err) -+ goto out; -+ -+ if (d_is_whiteout(next.dentry)) { -+ dput(next.dentry); -+ break; -+ } -+ -+ if (!next.dentry->d_inode) { -+ dput(next.dentry); -+ continue; -+ } -+ -+ /* only directories can be part of a union stack */ -+ if (!S_ISDIR(next.dentry->d_inode->i_mode)) { -+ dput(next.dentry); -+ break; -+ } -+ -+ /* now we know we found something "real" */ -+ append_to_union(last.mnt, last.dentry, next.mnt, next.dentry); -+ -+ if (last.dentry != path->dentry) -+ path_put(&last); -+ last.dentry = next.dentry; -+ last.mnt = mntget(next.mnt); -+ } -+ -+ if (last.dentry != path->dentry) -+ path_put(&last); -+out: -+ return err; -+} -+ -+static int real_lookup_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt }; -+ int res ; -+ -+ path_get(&safe); -+ res = __real_lookup_topmost(nd, name, path); -+ if (res) -+ goto out; -+ -+ /* only directories can be part of a union stack */ -+ if (!path->dentry->d_inode || -+ !S_ISDIR(path->dentry->d_inode->i_mode)) -+ goto out; -+ -+ /* Build the union stack for this part */ -+ res = __real_lookup_build_union(nd, name, path); -+ if (res) { -+ dput(path->dentry); -+ if (path->mnt != safe.mnt) -+ mntput(path->mnt); -+ goto out; -+ } -+ -+out: -+ path_put(&nd->path); -+ nd->path.dentry = safe.dentry; -+ nd->path.mnt = safe.mnt; -+ return res; - } - - /* -@@ -629,11 +1008,8 @@ static __always_inline int __do_follow_l - touch_atime(path->mnt, dentry); - nd_set_link(nd, NULL); - -- if (path->mnt != nd->path.mnt) { -- path_to_nameidata(path, nd); -- dget(dentry); -- } -- mntget(path->mnt); -+ if (path->mnt == nd->path.mnt) -+ mntget(nd->path.mnt); - cookie = dentry->d_inode->i_op->follow_link(dentry, nd); - error = PTR_ERR(cookie); - if (!IS_ERR(cookie)) { -@@ -721,7 +1097,7 @@ static int __follow_mount(struct path *p - return res; - } - --static void follow_mount(struct path *path) -+void follow_mount(struct path *path) - { - while (d_mountpoint(path->dentry)) { - struct vfsmount *mounted = lookup_mnt(path); -@@ -786,6 +1162,7 @@ static __always_inline void follow_dotdo - nd->path.mnt = parent; - } - follow_mount(&nd->path); -+ follow_union_mount(&nd->path); - } - - /* -@@ -796,35 +1173,55 @@ static __always_inline void follow_dotdo - static int do_lookup(struct nameidata *nd, struct qstr *name, - struct path *path) - { -- struct vfsmount *mnt = nd->path.mnt; -- struct dentry *dentry = __d_lookup(nd->path.dentry, name); -+ int err; -+ -+ if (IS_MNT_UNION(nd->path.mnt)) -+ goto need_union_lookup; - -- if (!dentry) -+ path->dentry = __d_lookup(nd->path.dentry, name); -+ path->mnt = nd->path.mnt; -+ if (!path->dentry) - goto need_lookup; -- if (dentry->d_op && dentry->d_op->d_revalidate) -+ if (path->dentry->d_op && path->dentry->d_op->d_revalidate) - goto need_revalidate; -+ - done: -- path->mnt = mnt; -- path->dentry = dentry; -- __follow_mount(path); -+ if (nd->path.mnt != path->mnt) { -+ nd->um_flags |= LAST_LOWLEVEL; -+ follow_mount(path); -+ } else -+ __follow_mount(path); -+ follow_union_mount(path); - return 0; - - need_lookup: -- dentry = real_lookup(nd->path.dentry, name, nd); -- if (IS_ERR(dentry)) -+ err = real_lookup(nd, name, path); -+ if (err) -+ goto fail; -+ goto done; -+ -+need_union_lookup: -+ err = cache_lookup_union(nd, name, path); -+ if (!err && path->dentry) -+ goto done; -+ -+ err = real_lookup_union(nd, name, path); -+ if (err) - goto fail; - goto done; - - need_revalidate: -- dentry = do_revalidate(dentry, nd); -- if (!dentry) -+ path->dentry = do_revalidate(path->dentry, nd); -+ if (!path->dentry) - goto need_lookup; -- if (IS_ERR(dentry)) -+ if (IS_ERR(path->dentry)) { -+ err = PTR_ERR(path->dentry); - goto fail; -+ } - goto done; - - fail: -- return PTR_ERR(dentry); -+ return err; - } - - /* -@@ -851,6 +1248,8 @@ static int __link_path_walk(const char * - if (nd->depth) - lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE); - -+ follow_union_mount(&nd->path); -+ - /* At this point we know we have a real path component. */ - for(;;) { - unsigned long hash; -@@ -913,6 +1312,44 @@ static int __link_path_walk(const char * - if (err) - break; - -+ /* -+ * We want to create this element on the top level -+ * file system in two cases: -+ * -+ * - We are specifically told to - LOOKUP_TOPMOST. -+ * - This is a directory, and it does not yet exist on -+ * the top level. Various tricks only work if -+ * directories always exist on the top level. -+ * -+ * In either case, only create this element on the top -+ * level if the last element is located on the lower -+ * level. If the last element is located on the top -+ * level, then every single element in the path -+ * already exists on the top level. -+ * -+ * Note that we can assume that the parent is on the -+ * top level since we always create the directory on -+ * the top level. -+ */ -+ -+ if ((nd->um_flags & LAST_LOWLEVEL) && -+ ((next.dentry->d_inode && -+ S_ISDIR(next.dentry->d_inode->i_mode) && -+ (nd->path.mnt != next.mnt)) || -+ (nd->flags & LOOKUP_TOPMOST))) { -+ struct dentry *dentry; -+ -+ dentry = union_create_topmost(nd, &this, &next); -+ if (IS_ERR(dentry)) { -+ err = PTR_ERR(dentry); -+ goto out_dput; -+ } -+ path_put_conditional(&next, nd); -+ next.mnt = nd->path.mnt; -+ next.dentry = dentry; -+ nd->um_flags &= ~LAST_LOWLEVEL; -+ } -+ - err = -ENOENT; - inode = next.dentry->d_inode; - if (!inode) -@@ -962,6 +1399,25 @@ last_component: - err = do_lookup(nd, &this, &next); - if (err) - break; -+ -+ if ((nd->um_flags & LAST_LOWLEVEL) && -+ ((next.dentry->d_inode && -+ S_ISDIR(next.dentry->d_inode->i_mode) && -+ (nd->path.mnt != next.mnt)) || -+ (nd->flags & LOOKUP_TOPMOST))) { -+ struct dentry *dentry; -+ -+ dentry = union_create_topmost(nd, &this, &next); -+ if (IS_ERR(dentry)) { -+ err = PTR_ERR(dentry); -+ goto out_dput; -+ } -+ path_put_conditional(&next, nd); -+ next.mnt = nd->path.mnt; -+ next.dentry = dentry; -+ nd->um_flags &= ~LAST_LOWLEVEL; -+ } -+ - inode = next.dentry->d_inode; - if ((lookup_flags & LOOKUP_FOLLOW) - && inode && inode->i_op->follow_link) { -@@ -1029,6 +1485,7 @@ static int path_init(int dfd, const char - - nd->last_type = LAST_ROOT; /* if there are only slashes... */ - nd->flags = flags; -+ nd->um_flags = 0; - nd->depth = 0; - nd->root.mnt = NULL; - -@@ -1172,61 +1629,437 @@ static int path_lookup_open(int dfd, con - } - - static struct dentry *__lookup_hash(struct qstr *name, -- struct dentry *base, struct nameidata *nd) -+ struct dentry *base, struct nameidata *nd) -+{ -+ struct dentry *dentry; -+ struct inode *inode; -+ int err; -+ -+ inode = base->d_inode; -+ -+ /* -+ * See if the low-level filesystem might want -+ * to use its own hash.. -+ */ -+ if (base->d_op && base->d_op->d_hash) { -+ err = base->d_op->d_hash(base, name); -+ dentry = ERR_PTR(err); -+ if (err < 0) -+ goto out; -+ } -+ -+ dentry = cache_lookup(base, name, nd); -+ if (!dentry) { -+ struct dentry *new; -+ -+ /* Don't create child dentry for a dead directory. */ -+ dentry = ERR_PTR(-ENOENT); -+ if (IS_DEADDIR(inode)) -+ goto out; -+ -+ new = d_alloc(base, name); -+ dentry = ERR_PTR(-ENOMEM); -+ if (!new) -+ goto out; -+ dentry = inode->i_op->lookup(inode, new, nd); -+ if (!dentry) -+ dentry = new; -+ else -+ dput(new); -+ } -+out: -+ return dentry; -+} -+ -+/* -+ * Restricted form of lookup. Doesn't follow links, single-component only, -+ * needs parent already locked. Doesn't follow mounts. -+ * SMP-safe. -+ */ -+static int lookup_hash(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ int err; -+ -+ err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC); -+ if (err) -+ return err; -+ path->mnt = nd->path.mnt; -+ path->dentry = __lookup_hash(name, nd->path.dentry, nd); -+ if (IS_ERR(path->dentry)) { -+ err = PTR_ERR(path->dentry); -+ path->dentry = NULL; -+ path->mnt = NULL; -+ } -+ return err; -+} -+ -+static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path next; -+ int err; -+ -+ err = lookup_hash(nd, name, path); -+ if (err) -+ return err; -+ -+ if (path->dentry->d_inode || d_is_whiteout(path->dentry)) -+ return 0; -+ -+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry)) -+ return 0; -+ -+ while (follow_union_down(&nd->path)) { -+ name->hash = full_name_hash(name->name, name->len); -+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) { -+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry, -+ name); -+ if (err < 0) -+ goto out; -+ } -+ -+ mutex_lock(&nd->path.dentry->d_inode->i_mutex); -+ err = lookup_hash(nd, name, &next); -+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex); -+ if (err) -+ goto out; -+ -+ if (next.dentry->d_inode || d_is_whiteout(next.dentry)) { -+ dput(path->dentry); -+ mntget(next.mnt); -+ *path = next; -+ goto out; -+ } -+ -+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry)) -+ goto out; -+ -+ dput(next.dentry); -+ } -+out: -+ if (err) -+ dput(path->dentry); -+ return err; -+} -+ -+static int __hash_lookup_build_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path last = *path; -+ struct path next; -+ int err = 0; -+ -+ while (follow_union_down(&nd->path)) { -+ /* We need to recompute the hash for lower layer lookups */ -+ name->hash = full_name_hash(name->name, name->len); -+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) { -+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry, -+ name); -+ if (err < 0) -+ goto out; -+ } -+ -+ mutex_lock(&nd->path.dentry->d_inode->i_mutex); -+ err = lookup_hash(nd, name, &next); -+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex); -+ if (err) -+ goto out; -+ -+ if (d_is_whiteout(next.dentry)) { -+ dput(next.dentry); -+ break; -+ } -+ -+ if (!next.dentry->d_inode) { -+ dput(next.dentry); -+ continue; -+ } -+ -+ /* only directories can be part of a union stack */ -+ if (!S_ISDIR(next.dentry->d_inode->i_mode)) { -+ dput(next.dentry); -+ break; -+ } -+ -+ /* now we know we found something "real" */ -+ append_to_union(last.mnt, last.dentry, next.mnt, next.dentry); -+ -+ if (last.dentry != path->dentry) -+ path_put(&last); -+ last.dentry = next.dentry; -+ last.mnt = mntget(next.mnt); -+ } -+ -+ if (last.dentry != path->dentry) -+ path_put(&last); -+out: -+ return err; -+} -+ -+int hash_lookup_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt }; -+ int res ; -+ -+ path_get(&safe); -+ res = __hash_lookup_topmost(nd, name, path); -+ if (res) -+ goto out; -+ -+ /* only directories can be part of a union stack */ -+ if (!path->dentry->d_inode || -+ !S_ISDIR(path->dentry->d_inode->i_mode)) -+ goto out; -+ -+ /* Build the union stack for this part */ -+ res = __hash_lookup_build_union(nd, name, path); -+ if (res) { -+ dput(path->dentry); -+ if (path->mnt != safe.mnt) -+ mntput(path->mnt); -+ goto out; -+ } -+ -+out: -+ path_put(&nd->path); -+ nd->path.dentry = safe.dentry; -+ nd->path.mnt = safe.mnt; -+ return res; -+} -+ -+/** -+ * do_union_hash_lookup() - walk down the union stack and lookup_hash() -+ * @nd: nameidata of parent to lookup from -+ * @name: pathname component to lookup -+ * @path: path to store result of lookup in -+ * -+ * Walk down the union stack and search for single pathname component name. It -+ * is assumed that the caller already did a lookup_hash() in the topmost parent -+ * that gave negative lookup result. Therefore this does call lookup_hash() in -+ * every lower layer (!) of the union stack. If a directory is found the union -+ * stack for that is assembled as well. -+ * -+ * Note: -+ * The caller needs to take care of holding a valid reference to the topmost -+ * parent. -+ * On error we leave @path untouched as well as when we don't find anything. -+ */ -+static int do_union_hash_lookup(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path next; -+ int err = 0; -+ -+ while (follow_union_down(&nd->path)) { -+ /* rehash because of d_op->d_hash() by the previous layer */ -+ name->hash = full_name_hash(name->name, name->len); -+ -+ mutex_lock(&nd->path.dentry->d_inode->i_mutex); -+ err = lookup_hash(nd, name, &next); -+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex); -+ -+ if (err) -+ break; -+ -+ if (next.dentry->d_inode) { -+ mntget(next.mnt); -+ if (!S_ISDIR(next.dentry->d_inode->i_mode)) { -+ *path = next; -+ break; -+ } -+ err = __hash_lookup_build_union(nd, name, &next); -+ if (err) -+ path_put(&next); -+ else -+ *path = next; -+ break; -+ } -+ -+ path_put_conditional(&next, nd); -+ -+ if ((IS_OPAQUE(nd->path.dentry->d_inode) && -+ !d_is_fallthru(next.dentry)) || -+ d_is_whiteout(next.dentry)) -+ break; -+ } -+ -+ return err; -+} -+ -+/** -+ * _hash_lookup_union() - lookup single pathname component -+ * @nd: nameidata of parent to lookup from -+ * @name: pathname component to lookup -+ * @path: path to store result of lookup in -+ * -+ * Returns the topmost parent locked and the target dentry found in the union -+ * or the topmost negative target dentry otherwise. -+ * -+ * Note: -+ * Returns topmost parent locked even on error. -+ */ -+static int _hash_lookup_union(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct path parent = nd->path; -+ struct path topmost; -+ int err; -+ -+ mutex_lock(&nd->path.dentry->d_inode->i_mutex); -+ err = lookup_hash(nd, name, path); -+ if (err) -+ return err; -+ -+ /* return if we found something and it isn't a directory we are done */ -+ if (path->dentry->d_inode && !S_ISDIR(path->dentry->d_inode->i_mode)) -+ return 0; -+ -+ /* stop lookup if the parent directory is marked opaque */ -+ if ((IS_OPAQUE(nd->path.dentry->d_inode) && -+ !d_is_fallthru(path->dentry)) || -+ d_is_whiteout(path->dentry)) -+ return 0; -+ -+ if (!strcmp(path->mnt->mnt_sb->s_type->name, "proc") || -+ !strcmp(path->mnt->mnt_sb->s_type->name, "sysfs")) -+ return 0; -+ -+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex); -+ -+ /* -+ * safe a reference to the topmost parent for walking the union stack -+ */ -+ path_get(&parent); -+ topmost = *path; -+ -+ if (path->dentry->d_inode && S_ISDIR(path->dentry->d_inode->i_mode)) { -+ err = __hash_lookup_build_union(nd, name, path); -+ if (err) -+ goto err_lock_parent; -+ goto out_lock_and_revalidate_parent; -+ } -+ -+ err = do_union_hash_lookup(nd, name, path); -+ if (err) -+ goto err_lock_parent; -+ -+out_lock_and_revalidate_parent: -+ /* seems that we haven't found anything, so return the topmost */ -+ path_to_nameidata(&parent, nd); -+ mutex_lock(&nd->path.dentry->d_inode->i_mutex); -+ -+ if (topmost.dentry == path->dentry) { -+ spin_lock(&path->dentry->d_lock); -+ if (nd->path.dentry != path->dentry->d_parent) { -+ spin_unlock(&path->dentry->d_lock); -+ dput(path->dentry); -+ name->hash = full_name_hash(name->name, name->len); -+ err = lookup_hash(nd, name, path); -+ if (err) -+ return err; -+ /* FIXME: What if we find a directory here ... */ -+ return err; -+ } -+ spin_unlock(&path->dentry->d_lock); -+ } else -+ dput(topmost.dentry); -+ -+ return 0; -+ -+err_lock_parent: -+ path_to_nameidata(&parent, nd); -+ path_put_conditional(path, nd); -+ mutex_lock(&nd->path.dentry->d_inode->i_mutex); -+ return err; -+} -+ -+/** -+ * lookup_rename_source() - lookup the source used by rename -+ * -+ * This is a special version of _hash_lookup_union() which becomes necessary -+ * for finding the source of a rename on union mounts. -+ * -+ * See comment for _hash_lookup_union() above. -+ */ -+static int lookup_rename_source(struct nameidata *oldnd, -+ struct nameidata *newnd, -+ struct dentry **trap, struct qstr *name, -+ struct path *old) - { -- struct dentry *dentry; -- struct inode *inode; -+ struct path parent = oldnd->path; -+ struct path topmost; - int err; - -- inode = base->d_inode; -+ err = lookup_hash(oldnd, name, old); -+ if (err) -+ return err; -+ -+ /* return if we found something and it isn't a directory we are done */ -+ if (old->dentry->d_inode && !S_ISDIR(old->dentry->d_inode->i_mode)) -+ return 0; -+ -+ /* stop lookup if the parent directory is marked opaque */ -+ if ((IS_OPAQUE(oldnd->path.dentry->d_inode) && -+ !d_is_fallthru(old->dentry)) || -+ d_is_whiteout(old->dentry)) -+ return 0; -+ -+ if (!strcmp(old->mnt->mnt_sb->s_type->name, "proc") || -+ !strcmp(old->mnt->mnt_sb->s_type->name, "sysfs")) -+ return 0; -+ -+ unlock_rename(oldnd->path.dentry, newnd->path.dentry); - - /* -- * See if the low-level filesystem might want -- * to use its own hash.. -+ * safe a reference to the topmost parent for walking the union stack - */ -- if (base->d_op && base->d_op->d_hash) { -- err = base->d_op->d_hash(base, name); -- dentry = ERR_PTR(err); -- if (err < 0) -- goto out; -+ path_get(&parent); -+ topmost = *old; -+ -+ if (old->dentry->d_inode && S_ISDIR(old->dentry->d_inode->i_mode)) { -+ err = __hash_lookup_build_union(oldnd, name, old); -+ if (err) -+ goto err_lock; -+ goto out_lock_and_revalidate_parent; - } - -- dentry = cached_lookup(base, name, nd); -- if (!dentry) { -- struct dentry *new; -+ err = do_union_hash_lookup(oldnd, name, old); -+ if (err) -+ goto err_lock; - -- /* Don't create child dentry for a dead directory. */ -- dentry = ERR_PTR(-ENOENT); -- if (IS_DEADDIR(inode)) -- goto out; -+out_lock_and_revalidate_parent: -+ path_to_nameidata(&parent, oldnd); -+ *trap = lock_rename(oldnd->path.dentry, newnd->path.dentry); - -- new = d_alloc(base, name); -- dentry = ERR_PTR(-ENOMEM); -- if (!new) -- goto out; -- dentry = inode->i_op->lookup(inode, new, nd); -- if (!dentry) -- dentry = new; -- else -- dput(new); -- } --out: -- return dentry; --} -+ /* -+ * If we return the topmost dentry we have to make sure that it has not -+ * been moved away while we gave up the topmost parents i_mutex lock. -+ */ -+ if (topmost.dentry == old->dentry) { -+ spin_lock(&old->dentry->d_lock); -+ if (oldnd->path.dentry != old->dentry->d_parent) { -+ spin_unlock(&old->dentry->d_lock); -+ dput(old->dentry); -+ name->hash = full_name_hash(name->name, name->len); -+ err = lookup_hash(oldnd, name, old); -+ if (err) -+ return err; -+ /* FIXME: What if we find a directory here ... */ -+ return err; -+ } -+ spin_unlock(&old->dentry->d_lock); -+ } else -+ dput(topmost.dentry); - --/* -- * Restricted form of lookup. Doesn't follow links, single-component only, -- * needs parent already locked. Doesn't follow mounts. -- * SMP-safe. -- */ --static struct dentry *lookup_hash(struct nameidata *nd) --{ -- int err; -+ return 0; - -- err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC); -- if (err) -- return ERR_PTR(err); -- return __lookup_hash(&nd->last, nd->path.dentry, nd); -+err_lock: -+ path_to_nameidata(&parent, oldnd); -+ path_put_conditional(old, oldnd); -+ *trap = lock_rename(oldnd->path.dentry, newnd->path.dentry); -+ return err; - } - - static int __lookup_one_len(const char *name, struct qstr *this, -@@ -1502,8 +2335,9 @@ int vfs_create(struct inode *dir, struct - return error; - } - --int may_open(struct path *path, int acc_mode, int flag) -+int may_open(struct nameidata *nd, int acc_mode, int flag) - { -+ struct path *path = &nd->path; - struct dentry *dentry = path->dentry; - struct inode *inode = dentry->d_inode; - int error; -@@ -1529,7 +2363,7 @@ int may_open(struct path *path, int acc_ - break; - } - -- error = inode_permission(inode, acc_mode); -+ error = union_permission(path, acc_mode); - if (error) - return error; - -@@ -1577,6 +2411,9 @@ int may_open(struct path *path, int acc_ - if (!error) - error = security_path_truncate(path, 0, - ATTR_MTIME|ATTR_CTIME|ATTR_OPEN); -+ /* XXX don't copy up file data */ -+ if (is_unionized(path->dentry, path->mnt)) -+ error = union_copyup(nd, flag /* XXX not used */); - if (!error) { - vfs_dq_init(inode); - -@@ -1623,7 +2460,7 @@ out_unlock: - if (error) - return error; - /* Don't check for write permission, don't truncate */ -- return may_open(&nd->path, 0, flag & ~O_TRUNC); -+ return may_open(nd, 0, flag & ~O_TRUNC); - } - - /* -@@ -1738,12 +2575,10 @@ struct file *do_filp_open(int dfd, const - if (flag & O_EXCL) - nd.flags |= LOOKUP_EXCL; - mutex_lock(&dir->d_inode->i_mutex); -- path.dentry = lookup_hash(&nd); -- path.mnt = nd.path.mnt; -+ error = hash_lookup_union(&nd, &nd.last, &path); - - do_last: -- error = PTR_ERR(path.dentry); -- if (IS_ERR(path.dentry)) { -+ if (error) { - mutex_unlock(&dir->d_inode->i_mutex); - goto exit; - } -@@ -1803,10 +2638,23 @@ do_last: - if (path.dentry->d_inode->i_op->follow_link) - goto do_link; - -- path_to_nameidata(&path, &nd); - error = -EISDIR; - if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode)) -- goto exit; -+ goto exit_dput; -+ -+ /* -+ * If this file is on a lower layer of the union stack, copy it to the -+ * topmost layer before opening it -+ */ -+ if (path.dentry->d_inode && -+ (path.dentry->d_parent != dir) && -+ S_ISREG(path.dentry->d_inode->i_mode)) { -+ error = __union_copyup(&path, &nd, &path); -+ if (error) -+ goto exit_dput; -+ } -+ -+ path_to_nameidata(&path, &nd); - ok: - /* - * Consider: -@@ -1824,12 +2672,18 @@ ok: - if (error) - goto exit; - } -- error = may_open(&nd.path, acc_mode, flag); -+ error = may_open(&nd, acc_mode, flag); - if (error) { - if (will_write) - mnt_drop_write(nd.path.mnt); - goto exit; - } -+ /* Okay, all permissions go, now copy up */ -+ if (!(flag & O_CREAT) && (flag & FMODE_WRITE)) { -+ error = union_copyup(&nd, flag /* XXX not used */); -+ if (error) -+ goto exit; -+ } - filp = nameidata_to_filp(&nd, open_flag); - if (IS_ERR(filp)) - ima_counts_put(&nd.path, -@@ -1904,8 +2758,7 @@ do_link: - } - dir = nd.path.dentry; - mutex_lock(&dir->d_inode->i_mutex); -- path.dentry = lookup_hash(&nd); -- path.mnt = nd.path.mnt; -+ error = hash_lookup_union(&nd, &nd.last, &path); - __putname(nd.last.name); - goto do_last; - } -@@ -1939,7 +2792,8 @@ EXPORT_SYMBOL(filp_open); - */ - struct dentry *lookup_create(struct nameidata *nd, int is_dir) - { -- struct dentry *dentry = ERR_PTR(-EEXIST); -+ struct path path = { .dentry = ERR_PTR(-EEXIST) } ; -+ int err; - - mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); - /* -@@ -1955,11 +2809,13 @@ struct dentry *lookup_create(struct name - /* - * Do the final lookup. - */ -- dentry = lookup_hash(nd); -- if (IS_ERR(dentry)) -+ err = hash_lookup_union(nd, &nd->last, &path); -+ if (err) { -+ path.dentry = ERR_PTR(err); - goto fail; -+ } - -- if (dentry->d_inode) -+ if (path.dentry->d_inode) - goto eexist; - /* - * Special case - lookup gave negative, but... we had foo/bar/ -@@ -1968,15 +2824,17 @@ struct dentry *lookup_create(struct name - * been asking for (non-existent) directory. -ENOENT for you. - */ - if (unlikely(!is_dir && nd->last.name[nd->last.len])) { -- dput(dentry); -- dentry = ERR_PTR(-ENOENT); -+ path_put_conditional(&path, nd); -+ path.dentry = ERR_PTR(-ENOENT); - } -- return dentry; -+ if (nd->path.mnt != path.mnt) -+ mntput(path.mnt); -+ return path.dentry; - eexist: -- dput(dentry); -- dentry = ERR_PTR(-EEXIST); -+ path_put_conditional(&path, nd); -+ path.dentry = ERR_PTR(-EEXIST); - fail: -- return dentry; -+ return path.dentry; - } - EXPORT_SYMBOL_GPL(lookup_create); - -@@ -2088,6 +2946,7 @@ SYSCALL_DEFINE3(mknod, const char __user - int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) - { - int error = may_create(dir, dentry); -+ int opaque = 0; - - if (error) - return error; -@@ -2101,9 +2960,18 @@ int vfs_mkdir(struct inode *dir, struct - return error; - - vfs_dq_init(dir); -+ -+ if (d_is_whiteout(dentry)) -+ opaque = 1; -+ - error = dir->i_op->mkdir(dir, dentry, mode); -- if (!error) -+ if (!error) { - fsnotify_mkdir(dir, dentry); -+ if (opaque) { -+ dentry->d_inode->i_flags |= S_OPAQUE; -+ mark_inode_dirty(dentry->d_inode); -+ } -+ } - return error; - } - -@@ -2149,6 +3017,212 @@ SYSCALL_DEFINE2(mkdir, const char __user - return sys_mkdirat(AT_FDCWD, pathname, mode); - } - -+ -+/* Checks on the victim for whiteout */ -+static inline int may_whiteout(struct inode *dir, struct dentry *victim, -+ int isdir) -+{ -+ int err; -+ -+ /* from may_create() */ -+ if (IS_DEADDIR(dir)) -+ return -ENOENT; -+ err = inode_permission(dir, MAY_WRITE | MAY_EXEC); -+ if (err) -+ return err; -+ -+ /* from may_delete() */ -+ if (IS_APPEND(dir)) -+ return -EPERM; -+ if (!victim->d_inode) -+ return 0; -+ if (check_sticky(dir, victim->d_inode) || -+ IS_APPEND(victim->d_inode) || -+ IS_IMMUTABLE(victim->d_inode)) -+ return -EPERM; -+ if (isdir) { -+ if (!S_ISDIR(victim->d_inode->i_mode)) -+ return -ENOTDIR; -+ if (IS_ROOT(victim)) -+ return -EBUSY; -+ } else if (S_ISDIR(victim->d_inode->i_mode)) -+ return -EISDIR; -+ if (victim->d_flags & DCACHE_NFSFS_RENAMED) -+ return -EBUSY; -+ return 0; -+} -+ -+/** -+ * vfs_whiteout: creates a white-out for the given directory entry -+ * @dir: parent inode -+ * @dentry: directory entry to white-out -+ * -+ * Simply white-out a given directory entry. This functionality is usually used -+ * in the sense of unlink. Therefore the given dentry can still be in-use and -+ * contains an in-use inode. The filesystem has to do what unlink or rmdir -+ * would in that case. Since the dentry still might be in-use we have to -+ * provide a fresh unhashed dentry that whiteout can fill the new inode into. -+ * In that case the given dentry is dropped and the fresh dentry containing the -+ * whiteout is rehashed instead. If the given dentry is unused, the whiteout -+ * inode is instantiated into it instead. -+ * -+ * After this returns with success, don't make any assumptions about the inode. -+ * Just dput() it dentry. -+ */ -+static int vfs_whiteout(struct inode *dir, struct dentry *dentry, int isdir) -+{ -+ int err; -+ struct inode *old_inode = dentry->d_inode; -+ struct dentry *parent, *whiteout; -+ -+ err = may_whiteout(dir, dentry, isdir); -+ if (err) -+ return err; -+ -+ BUG_ON(dentry->d_parent->d_inode != dir); -+ -+ if (!dir->i_op || !dir->i_op->whiteout) -+ return -EOPNOTSUPP; -+ -+ if (old_inode) { -+ vfs_dq_init(dir); -+ -+ mutex_lock(&old_inode->i_mutex); -+ if (isdir) -+ dentry_unhash(dentry); -+ if (d_mountpoint(dentry)) -+ err = -EBUSY; -+ else { -+ if (isdir) -+ err = security_inode_rmdir(dir, dentry); -+ else -+ err = security_inode_unlink(dir, dentry); -+ } -+ } -+ -+ parent = dget_parent(dentry); -+ whiteout = d_alloc_name(parent, dentry->d_name.name); -+ -+ if (!err) -+ err = dir->i_op->whiteout(dir, dentry, whiteout); -+ -+ if (old_inode) { -+ mutex_unlock(&old_inode->i_mutex); -+ if (!err) { -+ fsnotify_link_count(old_inode); -+ d_delete(dentry); -+ } -+ if (isdir) -+ dput(dentry); -+ } -+ -+ dput(whiteout); -+ dput(parent); -+ return err; -+} -+ -+int path_whiteout(struct path *dir_path, struct dentry *dentry, int isdir) -+{ -+ int error = mnt_want_write(dir_path->mnt); -+ -+ if (!error) { -+ error = vfs_whiteout(dir_path->dentry->d_inode, dentry, isdir); -+ mnt_drop_write(dir_path->mnt); -+ } -+ -+ return error; -+} -+EXPORT_SYMBOL(path_whiteout); -+ -+/* -+ * This is abusing readdir to check if a union directory is logically empty. -+ * Al Viro barfed when he saw this, but Val said: "Well, at this point I'm -+ * aiming for working, pretty can come later" -+ */ -+static int filldir_is_empty(void *__buf, const char *name, int namlen, -+ loff_t offset, u64 ino, unsigned int d_type) -+{ -+ int *is_empty = (int *)__buf; -+ -+ switch (namlen) { -+ case 2: -+ if (name[1] != '.') -+ break; -+ case 1: -+ if (name[0] != '.') -+ break; -+ return 0; -+ } -+ -+ if (d_type == DT_WHT) -+ return 0; -+ -+ (*is_empty) = 0; -+ return 0; -+} -+ -+static int directory_is_empty(struct dentry *dentry, struct vfsmount *mnt) -+{ -+ struct file *file; -+ int err; -+ int is_empty = 1; -+ -+ BUG_ON(!S_ISDIR(dentry->d_inode->i_mode)); -+ -+ /* references for the file pointer */ -+ dget(dentry); -+ mntget(mnt); -+ -+ file = dentry_open(dentry, mnt, O_RDONLY, current_cred()); -+ if (IS_ERR(file)) -+ return 0; -+ -+ err = vfs_readdir(file, filldir_is_empty, &is_empty); -+ -+ fput(file); -+ return is_empty; -+} -+ -+static int do_whiteout(struct nameidata *nd, struct path *path, int isdir) -+{ -+ struct path safe = { .dentry = dget(nd->path.dentry), -+ .mnt = mntget(nd->path.mnt) }; -+ struct dentry *dentry = path->dentry; -+ int err; -+ -+ err = may_whiteout(nd->path.dentry->d_inode, dentry, isdir); -+ if (err) -+ goto out; -+ -+ err = -ENOENT; -+ if (!dentry->d_inode) -+ goto out; -+ -+ err = -ENOTEMPTY; -+ if (isdir && !directory_is_empty(path->dentry, path->mnt)) -+ goto out; -+ -+ if (nd->path.dentry != dentry->d_parent) { -+ dentry = __lookup_hash(&path->dentry->d_name, nd->path.dentry, -+ nd); -+ err = PTR_ERR(dentry); -+ if (IS_ERR(dentry)) -+ goto out; -+ -+ dput(path->dentry); -+ if (path->mnt != safe.mnt) -+ mntput(path->mnt); -+ path->mnt = nd->path.mnt; -+ path->dentry = dentry; -+ } -+ -+ err = vfs_whiteout(nd->path.dentry->d_inode, dentry, isdir); -+ -+out: -+ path_put(&safe); -+ return err; -+} -+ - /* - * We try to drop the dentry early: we should have - * a usage count of 2 if we're the only user of this -@@ -2213,7 +3287,7 @@ static long do_rmdir(int dfd, const char - { - int error = 0; - char * name; -- struct dentry *dentry; -+ struct path path; - struct nameidata nd; - - error = user_path_parent(dfd, pathname, &nd, &name); -@@ -2235,21 +3309,24 @@ static long do_rmdir(int dfd, const char - nd.flags &= ~LOOKUP_PARENT; - - mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); -- dentry = lookup_hash(&nd); -- error = PTR_ERR(dentry); -- if (IS_ERR(dentry)) -+ error = hash_lookup_union(&nd, &nd.last, &path); -+ if (error) - goto exit2; -+ if (is_unionized(nd.path.dentry, nd.path.mnt)) { -+ error = do_whiteout(&nd, &path, 1); -+ goto exit3; -+ } - error = mnt_want_write(nd.path.mnt); - if (error) - goto exit3; -- error = security_path_rmdir(&nd.path, dentry); -+ error = security_path_rmdir(&nd.path, path.dentry); - if (error) - goto exit4; -- error = vfs_rmdir(nd.path.dentry->d_inode, dentry); -+ error = vfs_rmdir(nd.path.dentry->d_inode, path.dentry); - exit4: - mnt_drop_write(nd.path.mnt); - exit3: -- dput(dentry); -+ path_put_conditional(&path, &nd); - exit2: - mutex_unlock(&nd.path.dentry->d_inode->i_mutex); - exit1: -@@ -2304,7 +3381,7 @@ static long do_unlinkat(int dfd, const c - { - int error; - char *name; -- struct dentry *dentry; -+ struct path path; - struct nameidata nd; - struct inode *inode = NULL; - -@@ -2319,26 +3396,29 @@ static long do_unlinkat(int dfd, const c - nd.flags &= ~LOOKUP_PARENT; - - mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); -- dentry = lookup_hash(&nd); -- error = PTR_ERR(dentry); -- if (!IS_ERR(dentry)) { -+ error = hash_lookup_union(&nd, &nd.last, &path); -+ if (!error) { - /* Why not before? Because we want correct error value */ - if (nd.last.name[nd.last.len]) - goto slashes; -- inode = dentry->d_inode; -+ inode = path.dentry->d_inode; - if (inode) - atomic_inc(&inode->i_count); -+ if (is_unionized(nd.path.dentry, nd.path.mnt)) { -+ error = do_whiteout(&nd, &path, 0); -+ goto exit2; -+ } - error = mnt_want_write(nd.path.mnt); - if (error) - goto exit2; -- error = security_path_unlink(&nd.path, dentry); -+ error = security_path_unlink(&nd.path, path.dentry); - if (error) - goto exit3; -- error = vfs_unlink(nd.path.dentry->d_inode, dentry); -+ error = vfs_unlink(nd.path.dentry->d_inode, path.dentry); - exit3: - mnt_drop_write(nd.path.mnt); - exit2: -- dput(dentry); -+ path_put_conditional(&path, &nd); - } - mutex_unlock(&nd.path.dentry->d_inode->i_mutex); - if (inode) -@@ -2349,8 +3429,8 @@ exit1: - return error; - - slashes: -- error = !dentry->d_inode ? -ENOENT : -- S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; -+ error = !path.dentry->d_inode ? -ENOENT : -+ S_ISDIR(path.dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; - goto exit2; - } - -@@ -2686,11 +3766,96 @@ int vfs_rename(struct inode *old_dir, st - return error; - } - -+static int vfs_rename_union(struct nameidata *oldnd, struct path *old, -+ struct nameidata *newnd, struct path *new) -+{ -+ struct inode *old_dir = oldnd->path.dentry->d_inode; -+ struct inode *new_dir = newnd->path.dentry->d_inode; -+ struct qstr old_name; -+ char *name; -+ struct dentry *dentry; -+ int error; -+ -+ if (old->dentry->d_inode == new->dentry->d_inode) -+ return 0; -+ error = may_whiteout(old_dir, old->dentry, 0); -+ if (error) -+ return error; -+ if (!old_dir->i_op || !old_dir->i_op->whiteout) -+ return -EPERM; -+ -+ if (!new->dentry->d_inode) -+ error = may_create(new_dir, new->dentry); -+ else -+ error = may_delete(new_dir, new->dentry, 0); -+ if (error) -+ return error; -+ -+ vfs_dq_init(old_dir); -+ vfs_dq_init(new_dir); -+ -+ error = -EBUSY; -+ if (d_mountpoint(old->dentry) || d_mountpoint(new->dentry)) -+ return error; -+ -+ error = -ENOMEM; -+ name = kmalloc(old->dentry->d_name.len, GFP_KERNEL); -+ if (!name) -+ return error; -+ strncpy(name, old->dentry->d_name.name, old->dentry->d_name.len); -+ name[old->dentry->d_name.len] = 0; -+ old_name.len = old->dentry->d_name.len; -+ old_name.hash = old->dentry->d_name.hash; -+ old_name.name = name; -+ -+ /* possibly delete the existing new file */ -+ if ((newnd->path.dentry == new->dentry->d_parent) && -+ new->dentry->d_inode) { -+ /* FIXME: inode may be truncated while we hold a lock */ -+ error = vfs_unlink(new_dir, new->dentry); -+ if (error) -+ goto freename; -+ -+ dentry = __lookup_hash(&new->dentry->d_name, -+ newnd->path.dentry, newnd); -+ if (IS_ERR(dentry)) -+ goto freename; -+ -+ dput(new->dentry); -+ new->dentry = dentry; -+ } -+ -+ /* copyup to the new file */ -+ error = __union_copyup(old, newnd, new); -+ if (error) -+ goto freename; -+ -+ /* whiteout the old file */ -+ dentry = __lookup_hash(&old_name, oldnd->path.dentry, oldnd); -+ error = PTR_ERR(dentry); -+ if (IS_ERR(dentry)) -+ goto freename; -+ error = vfs_whiteout(old_dir, dentry, 0); -+ dput(dentry); -+ -+ /* FIXME: This is acutally unlink() && create() ... */ -+/* -+ if (!error) { -+ const char *new_name = old_dentry->d_name.name; -+ fsnotify_move(old_dir, new_dir, old_name.name, new_name, 0, -+ new_dentry->d_inode, old_dentry->d_inode); -+ } -+*/ -+freename: -+ kfree(old_name.name); -+ return error; -+} -+ - SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, - int, newdfd, const char __user *, newname) - { - struct dentry *old_dir, *new_dir; -- struct dentry *old_dentry, *new_dentry; -+ struct path old, new; - struct dentry *trap; - struct nameidata oldnd, newnd; - char *from; -@@ -2724,16 +3889,28 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c - - trap = lock_rename(new_dir, old_dir); - -- old_dentry = lookup_hash(&oldnd); -- error = PTR_ERR(old_dentry); -- if (IS_ERR(old_dentry)) -+ /* -+ * For union mounts we need to call a giant lookup_rename_source() -+ * instead. -+ * First lock_rename() and look on the topmost fs like you would do in -+ * the normal rename, if you find something which is not a directory, -+ * go ahead and lookup target and do normal rename. -+ * If you find a negative dentry, unlock_rename() and continue as -+ * _hash_lookup_union() would do without locking the topmost parent -+ * at the end. After that do lock_rename() of the source parent and the -+ * target parent and do a copyup with additional whiteout creation at -+ * the end. -+ */ -+// error = hash_lookup_union(&oldnd, &oldnd.last, &old); -+ error = lookup_rename_source(&oldnd, &newnd, &trap, &oldnd.last, &old); -+ if (error) - goto exit3; - /* source must exist */ - error = -ENOENT; -- if (!old_dentry->d_inode) -+ if (!old.dentry->d_inode) - goto exit4; - /* unless the source is a directory trailing slashes give -ENOTDIR */ -- if (!S_ISDIR(old_dentry->d_inode->i_mode)) { -+ if (!S_ISDIR(old.dentry->d_inode->i_mode)) { - error = -ENOTDIR; - if (oldnd.last.name[oldnd.last.len]) - goto exit4; -@@ -2742,32 +3919,44 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c - } - /* source should not be ancestor of target */ - error = -EINVAL; -- if (old_dentry == trap) -+ if (old.dentry == trap) - goto exit4; -- new_dentry = lookup_hash(&newnd); -- error = PTR_ERR(new_dentry); -- if (IS_ERR(new_dentry)) -+ /* target is always on topmost fs, even with unions */ -+ error = lookup_hash(&newnd, &newnd.last, &new); -+ if (error) - goto exit4; - /* target should not be an ancestor of source */ - error = -ENOTEMPTY; -- if (new_dentry == trap) -+ if (new.dentry == trap) -+ goto exit5; -+ /* renaming of directories on unions is done by the user-space */ -+ error = -EXDEV; -+ if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) && -+ S_ISDIR(old.dentry->d_inode->i_mode)) - goto exit5; -+// if (is_unionized(newnd.path.dentry, newnd.path.mnt)) -+// goto exit5; - - error = mnt_want_write(oldnd.path.mnt); - if (error) - goto exit5; -- error = security_path_rename(&oldnd.path, old_dentry, -- &newnd.path, new_dentry); -+ error = security_path_rename(&oldnd.path, old.dentry, -+ &newnd.path, new.dentry); - if (error) - goto exit6; -- error = vfs_rename(old_dir->d_inode, old_dentry, -- new_dir->d_inode, new_dentry); -+ if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) && -+ (old.dentry->d_parent != oldnd.path.dentry)) { -+ error = vfs_rename_union(&oldnd, &old, &newnd, &new); -+ goto exit6; -+ } -+ error = vfs_rename(old_dir->d_inode, old.dentry, -+ new_dir->d_inode, new.dentry); - exit6: - mnt_drop_write(oldnd.path.mnt); - exit5: -- dput(new_dentry); -+ path_put_conditional(&new, &newnd); - exit4: -- dput(old_dentry); -+ path_put_conditional(&old, &oldnd); - exit3: - unlock_rename(new_dir, old_dir); - exit2: ---- a/fs/namespace.c -+++ b/fs/namespace.c -@@ -29,6 +29,7 @@ - #include <linux/log2.h> - #include <linux/idr.h> - #include <linux/fs_struct.h> -+#include <linux/union.h> - #include <asm/uaccess.h> - #include <asm/unistd.h> - #include "pnode.h" -@@ -150,6 +151,9 @@ struct vfsmount *alloc_vfsmnt(const char - INIT_LIST_HEAD(&mnt->mnt_share); - INIT_LIST_HEAD(&mnt->mnt_slave_list); - INIT_LIST_HEAD(&mnt->mnt_slave); -+#ifdef CONFIG_UNION_MOUNT -+ INIT_LIST_HEAD(&mnt->mnt_unions); -+#endif - #ifdef CONFIG_SMP - mnt->mnt_writers = alloc_percpu(int); - if (!mnt->mnt_writers) -@@ -469,6 +473,7 @@ static void __touch_mnt_namespace(struct - - static void detach_mnt(struct vfsmount *mnt, struct path *old_path) - { -+ detach_mnt_union(mnt); - old_path->dentry = mnt->mnt_mountpoint; - old_path->mnt = mnt->mnt_parent; - mnt->mnt_parent = mnt; -@@ -492,6 +497,7 @@ static void attach_mnt(struct vfsmount * - list_add_tail(&mnt->mnt_hash, mount_hashtable + - hash(path->mnt, path->dentry)); - list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts); -+ attach_mnt_union(mnt, path->mnt, path->dentry); - } - - /* -@@ -514,6 +520,7 @@ static void commit_tree(struct vfsmount - list_add_tail(&mnt->mnt_hash, mount_hashtable + - hash(parent, mnt->mnt_mountpoint)); - list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); -+ attach_mnt_union(mnt, mnt->mnt_parent, mnt->mnt_mountpoint); - touch_mnt_namespace(n); - } - -@@ -770,6 +777,7 @@ static void show_mnt_opts(struct seq_fil - { MNT_NODIRATIME, ",nodiratime" }, - { MNT_RELATIME, ",relatime" }, - { MNT_STRICTATIME, ",strictatime" }, -+ { MNT_UNION, ",union" }, - { 0, NULL } - }; - const struct proc_fs_info *fs_infop; -@@ -984,6 +992,7 @@ void release_mounts(struct list_head *he - struct dentry *dentry; - struct vfsmount *m; - spin_lock(&vfsmount_lock); -+ detach_mnt_union(mnt); - dentry = mnt->mnt_mountpoint; - m = mnt->mnt_parent; - mnt->mnt_mountpoint = mnt->mnt_root; -@@ -1102,6 +1111,11 @@ static int do_umount(struct vfsmount *mn - spin_unlock(&vfsmount_lock); - if (retval) - security_sb_umount_busy(mnt); -+ /* If this was a union mount, we are no longer a read-only -+ * user on the underlying mount */ -+ if (mnt->mnt_flags & MNT_UNION) -+ mnt->mnt_parent->mnt_sb->s_readonly_users--; -+ - up_write(&namespace_sem); - release_mounts(&umount_list); - return retval; -@@ -1426,6 +1440,10 @@ static int do_change_type(struct path *p - if (path->dentry != path->mnt->mnt_root) - return -EINVAL; - -+ /* Don't change the type of union mounts */ -+ if (IS_MNT_UNION(path->mnt)) -+ return -EINVAL; -+ - down_write(&namespace_sem); - if (type == MS_SHARED) { - err = invent_group_ids(mnt, recurse); -@@ -1444,10 +1462,65 @@ static int do_change_type(struct path *p - } - - /* -+ * Mount-time check of upper and lower layer file systems to see if we -+ * can union mount one on the other. -+ * -+ * Union mounts must follow these rules: -+ * -+ * - The lower layer must be read-only. This avoids lots of nasty -+ * unsolvable races where file system structures disappear suddenly. -+ * XXX - Checking the vfsmnt for read-only is a temporary hack; the -+ * file system could be mounted read-write elsewhere. We need to -+ * enforce read-only at the superblock level (patches coming). -+ * -+ * - The upper layer must be writable. This isn't an absolute -+ * requirement; right now we need it to make readdir() work since we -+ * copy up directory entries to the top level. A possible -+ * workaround is to mount a tmpfs file system transparently over the -+ * top. -+ * -+ * - The upper layer must support whiteouts and fallthrus (if it is -+ * writeable). -+ * -+ * - The lower layer must not also be a union mount. This is just to -+ * make life simpler for now, there is no inherent limitation on the -+ * number of layers. -+ * -+ * XXX - Check other mount flags for incompatibilities - I'm sure -+ * there are some. -+ */ -+ -+static int -+check_union_mnt(struct path *mntpnt, struct vfsmount *top_mnt, int mnt_flags) -+{ -+ struct vfsmount *lower_mnt = mntpnt->mnt; -+ -+ /* Is this even a union mount? */ -+ if (!(mnt_flags & MNT_UNION)) -+ return 0; -+ -+ /* Lower layer must be read-only and not a union mount */ -+ if (!(lower_mnt->mnt_sb->s_flags & MS_RDONLY) || -+ (lower_mnt->mnt_flags & MNT_UNION)) -+ return -EBUSY; -+ -+ /* Upper layer must be writable */ -+ if (mnt_flags & MNT_READONLY) -+ return -EROFS; -+ -+ /* Upper layer must support whiteouts and fallthrus */ -+ if (!(top_mnt->mnt_sb->s_flags & MS_WHITEOUT)) -+ return -EINVAL; -+ -+ /* All good! */ -+ return 0; -+} -+ -+/* - * do loopback mount. - */ --static int do_loopback(struct path *path, char *old_name, -- int recurse) -+static int do_loopback(struct path *path, char *old_name, int recurse, -+ int mnt_flags) - { - struct path old_path; - struct vfsmount *mnt = NULL; -@@ -1477,6 +1550,13 @@ static int do_loopback(struct path *path - if (!mnt) - goto out; - -+ err = check_union_mnt(&old_path, mnt, mnt_flags); -+ if (err) -+ goto out; -+ -+ if (mnt_flags & MNT_UNION) -+ mnt->mnt_flags |= MNT_UNION; -+ - err = graft_tree(mnt, path); - if (err) { - LIST_HEAD(umount_list); -@@ -1486,6 +1566,10 @@ static int do_loopback(struct path *path - release_mounts(&umount_list); - } - -+ /* If this is a union mount, add ourselves to the readonly users */ -+ if (mnt_flags & MNT_UNION) -+ mnt->mnt_parent->mnt_sb->s_readonly_users++; -+ - out: - up_write(&namespace_sem); - path_put(&old_path); -@@ -1570,6 +1654,13 @@ static int do_move_mount(struct path *pa - if (err) - return err; - -+ /* moving to or from a union mount is not supported */ -+ err = -EINVAL; -+ if (IS_MNT_UNION(path->mnt)) -+ goto exit; -+ if (IS_MNT_UNION(old_path.mnt)) -+ goto exit; -+ - down_write(&namespace_sem); - while (d_mountpoint(path->dentry) && - follow_down(path)) -@@ -1627,6 +1718,7 @@ out: - up_write(&namespace_sem); - if (!err) - path_put(&parent_path); -+exit: - path_put(&old_path); - return err; - } -@@ -1684,10 +1776,18 @@ int do_add_mount(struct vfsmount *newmnt - if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) - goto unlock; - -+ err = check_union_mnt(path, newmnt, mnt_flags); -+ if (err) -+ goto unlock; -+ - newmnt->mnt_flags = mnt_flags; - if ((err = graft_tree(newmnt, path))) - goto unlock; - -+ /* If this is a union mount, add ourselves to the readonly users */ -+ if (mnt_flags & MNT_UNION) -+ newmnt->mnt_parent->mnt_sb->s_readonly_users++; -+ - if (fslist) /* add to the specified expiration list */ - list_add_tail(&newmnt->mnt_expire, fslist); - -@@ -1940,10 +2040,12 @@ long do_mount(char *dev_name, char *dir_ - mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); - if (flags & MS_RDONLY) - mnt_flags |= MNT_READONLY; -+ if (flags & MS_UNION) -+ mnt_flags |= MNT_UNION; - - flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | - MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | -- MS_STRICTATIME); -+ MS_STRICTATIME | MS_UNION); - - /* ... and get the mountpoint */ - retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); -@@ -1959,7 +2061,8 @@ long do_mount(char *dev_name, char *dir_ - retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, - data_page); - else if (flags & MS_BIND) -- retval = do_loopback(&path, dev_name, flags & MS_REC); -+ retval = do_loopback(&path, dev_name, flags & MS_REC, -+ mnt_flags); - else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) - retval = do_change_type(&path, flags); - else if (flags & MS_MOVE) -@@ -2196,6 +2299,8 @@ SYSCALL_DEFINE2(pivot_root, const char _ - if (d_unlinked(old.dentry)) - goto out2; - error = -EBUSY; -+ follow_union_down(&new); -+ follow_union_down(&root); - if (new.mnt == root.mnt || - old.mnt == root.mnt) - goto out2; /* loop, on the same file system */ ---- a/fs/nfsctl.c -+++ b/fs/nfsctl.c -@@ -38,10 +38,10 @@ static struct file *do_open(char *name, - return ERR_PTR(error); - - if (flags == O_RDWR) -- error = may_open(&nd.path, MAY_READ|MAY_WRITE, -- FMODE_READ|FMODE_WRITE); -+ error = may_open(&nd, MAY_READ|MAY_WRITE, -+ FMODE_READ|FMODE_WRITE); - else -- error = may_open(&nd.path, MAY_WRITE, FMODE_WRITE); -+ error = may_open(&nd, MAY_WRITE, FMODE_WRITE); - - if (!error) - return dentry_open(nd.path.dentry, nd.path.mnt, flags, ---- a/fs/nfsd/nfs3xdr.c -+++ b/fs/nfsd/nfs3xdr.c -@@ -898,6 +898,11 @@ encode_entry(struct readdir_cd *ccd, con - int elen; /* estimated entry length in words */ - int num_entry_words = 0; /* actual number of words */ - -+ if (d_type == DT_WHT) { -+ cd->common.err = nfs_ok; -+ return 0; -+ } -+ - if (cd->offset) { - u64 offset64 = offset; - ---- a/fs/nfsd/nfs4xdr.c -+++ b/fs/nfsd/nfs4xdr.c -@@ -2261,7 +2261,7 @@ nfsd4_encode_dirent(void *ccdv, const ch - __be32 nfserr = nfserr_toosmall; - - /* In nfsv4, "." and ".." never make it onto the wire.. */ -- if (name && isdotent(name, namlen)) { -+ if (d_type == DT_WHT || (name && isdotent(name, namlen))) { - cd->common.err = nfs_ok; - return 0; - } ---- a/fs/nfsd/nfsxdr.c -+++ b/fs/nfsd/nfsxdr.c -@@ -513,6 +513,10 @@ nfssvc_encode_entry(void *ccdv, const ch - namlen, name, offset, ino); - */ - -+ if (d_type == DT_WHT) { -+ cd->common.err = nfs_ok; -+ return 0; -+ } - if (offset > ~((u32) 0)) { - cd->common.err = nfserr_fbig; - return -EINVAL; ---- a/fs/open.c -+++ b/fs/open.c -@@ -30,6 +30,7 @@ - #include <linux/audit.h> - #include <linux/falloc.h> - #include <linux/fs_struct.h> -+#include <linux/union.h> - - int vfs_statfs(struct dentry *dentry, struct kstatfs *buf) - { -@@ -224,69 +225,69 @@ int do_truncate(struct dentry *dentry, l - return ret; - } - --static long do_sys_truncate(const char __user *pathname, loff_t length) -+static int __do_ftruncate(struct file *file, unsigned long length, int small) - { -- struct path path; -- struct inode *inode; -+ struct inode * inode; -+ struct dentry *dentry; - int error; - - error = -EINVAL; -- if (length < 0) /* sorry, but loff_t says... */ -+ if (length < 0) - goto out; -+ /* explicitly opened as large or we are on 64-bit box */ -+ if (file->f_flags & O_LARGEFILE) -+ small = 0; - -- error = user_path(pathname, &path); -- if (error) -+ dentry = file->f_path.dentry; -+ inode = dentry->d_inode; -+ error = -EINVAL; -+ if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE)) - goto out; -- inode = path.dentry->d_inode; -- -- /* For directories it's -EISDIR, for other non-regulars - -EINVAL */ -- error = -EISDIR; -- if (S_ISDIR(inode->i_mode)) -- goto dput_and_out; - - error = -EINVAL; -- if (!S_ISREG(inode->i_mode)) -- goto dput_and_out; -- -- error = mnt_want_write(path.mnt); -- if (error) -- goto dput_and_out; -+ /* Cannot ftruncate over 2^31 bytes without large file support */ -+ if (small && length > MAX_NON_LFS) - -- error = inode_permission(inode, MAY_WRITE); -- if (error) -- goto mnt_drop_write_and_out; -+ goto out; - - error = -EPERM; - if (IS_APPEND(inode)) -- goto mnt_drop_write_and_out; -+ goto out; - -- error = get_write_access(inode); -- if (error) -- goto mnt_drop_write_and_out; -+ error = locks_verify_truncate(inode, file, length); -+ if (!error) -+ error = security_path_truncate(&file->f_path, length, -+ ATTR_MTIME|ATTR_CTIME); -+ if (!error) -+ /* Already copied up for union, opened with write */ -+ error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file); -+out: -+ return error; -+} - -- /* -- * Make sure that there are no leases. get_write_access() protects -- * against the truncate racing with a lease-granting setlease(). -- */ -- error = break_lease(inode, FMODE_WRITE); -- if (error) -- goto put_write_and_out; -+static long do_sys_truncate(const char __user *pathname, loff_t length) -+{ -+ struct file *file; -+ char *tmp; -+ int error; - -- error = locks_verify_truncate(inode, NULL, length); -- if (!error) -- error = security_path_truncate(&path, length, 0); -- if (!error) { -- vfs_dq_init(inode); -- error = do_truncate(path.dentry, length, 0, NULL); -- } -+ error = -EINVAL; -+ if (length < 0) /* sorry, but loff_t says... */ -+ return error; - --put_write_and_out: -- put_write_access(inode); --mnt_drop_write_and_out: -- mnt_drop_write(path.mnt); --dput_and_out: -- path_put(&path); --out: -+ tmp = getname(pathname); -+ if (IS_ERR(tmp)) -+ return PTR_ERR(tmp); -+ -+ file = filp_open(tmp, O_RDWR | O_LARGEFILE, 0); -+ putname(tmp); -+ -+ if (IS_ERR(file)) -+ return PTR_ERR(file); -+ -+ error = __do_ftruncate(file, length, 0); -+ -+ fput(file); - return error; - } - -@@ -297,45 +298,16 @@ SYSCALL_DEFINE2(truncate, const char __u - - static long do_sys_ftruncate(unsigned int fd, loff_t length, int small) - { -- struct inode * inode; -- struct dentry *dentry; - struct file * file; - int error; - -- error = -EINVAL; -- if (length < 0) -- goto out; - error = -EBADF; - file = fget(fd); - if (!file) - goto out; - -- /* explicitly opened as large or we are on 64-bit box */ -- if (file->f_flags & O_LARGEFILE) -- small = 0; -- -- dentry = file->f_path.dentry; -- inode = dentry->d_inode; -- error = -EINVAL; -- if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE)) -- goto out_putf; -- -- error = -EINVAL; -- /* Cannot ftruncate over 2^31 bytes without large file support */ -- if (small && length > MAX_NON_LFS) -- goto out_putf; -+ error = __do_ftruncate(file, length, small); - -- error = -EPERM; -- if (IS_APPEND(inode)) -- goto out_putf; -- -- error = locks_verify_truncate(inode, file, length); -- if (!error) -- error = security_path_truncate(&file->f_path, length, -- ATTR_MTIME|ATTR_CTIME); -- if (!error) -- error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file); --out_putf: - fput(file); - out: - return error; -@@ -494,7 +466,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con - goto out_path_release; - } - -- res = inode_permission(inode, mode | MAY_ACCESS); -+ res = union_permission(&path, mode | MAY_ACCESS); -+ - /* SuS v2 requires we report a read only fs too */ - if (res || !(mode & S_IWOTH) || special_file(inode->i_mode)) - goto out_path_release; -@@ -508,7 +481,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con - * inherently racy and know that the fs may change - * state before we even see this result. - */ -- if (__mnt_is_readonly(path.mnt)) -+ if ((!is_unionized(path.dentry, path.mnt) && -+ (__mnt_is_readonly(path.mnt)))) - res = -EROFS; - - out_path_release: -@@ -554,20 +528,19 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd - error = -EBADF; - file = fget(fd); - if (!file) -- goto out; -+ return error; - - inode = file->f_path.dentry->d_inode; - - error = -ENOTDIR; - if (!S_ISDIR(inode->i_mode)) -- goto out_putf; -+ goto out; - - error = inode_permission(inode, MAY_EXEC | MAY_ACCESS); - if (!error) - set_fs_pwd(current->fs, &file->f_path); --out_putf: -- fput(file); - out: -+ fput(file); - return error; - } - ---- a/fs/readdir.c -+++ b/fs/readdir.c -@@ -16,6 +16,7 @@ - #include <linux/security.h> - #include <linux/syscalls.h> - #include <linux/unistd.h> -+#include <linux/union.h> - - #include <asm/uaccess.h> - -@@ -36,9 +37,24 @@ int vfs_readdir(struct file *file, filld - - res = -ENOENT; - if (!IS_DEADDIR(inode)) { -+ /* -+ * XXX Think harder about locking for -+ * union_copyup_dir. Currently we lock the topmost -+ * directory and hold that lock while sequentially -+ * acquiring and dropping locks for the directories -+ * below this one in the union stack. -+ */ -+ if (is_unionized(file->f_path.dentry, file->f_path.mnt) && -+ !IS_OPAQUE(inode)) { -+ res = union_copyup_dir(&file->f_path); -+ if (res) -+ goto out_unlock; -+ } -+ - res = file->f_op->readdir(file, buf, filler); - file_accessed(file); - } -+out_unlock: - mutex_unlock(&inode->i_mutex); - out: - return res; -@@ -77,6 +93,9 @@ static int fillonedir(void * __buf, cons - struct old_linux_dirent __user * dirent; - unsigned long d_ino; - -+ if (d_type == DT_WHT) -+ return 0; -+ - if (buf->result) - return -EINVAL; - d_ino = ino; -@@ -154,6 +173,9 @@ static int filldir(void * __buf, const c - unsigned long d_ino; - int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(long)); - -+ if (d_type == DT_WHT) -+ return 0; -+ - buf->error = -EINVAL; /* only used if we fail.. */ - if (reclen > buf->count) - return -EINVAL; -@@ -239,6 +261,9 @@ static int filldir64(void * __buf, const - struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf; - int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 1, sizeof(u64)); - -+ if (d_type == DT_WHT) -+ return 0; -+ - buf->error = -EINVAL; /* only used if we fail.. */ - if (reclen > buf->count) - return -EINVAL; ---- a/fs/super.c -+++ b/fs/super.c -@@ -596,6 +596,15 @@ int do_remount_sb(struct super_block *sb - } - remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY); - -+ /* If we are remounting read/write, make sure that none of the -+ users require read-only for correct operation (such as -+ union mounts). */ -+ if (remount_rw && sb->s_readonly_users) { -+ printk(KERN_INFO "%s: In use by %d read-only user(s)\n", -+ sb->s_id, sb->s_readonly_users); -+ return -EROFS; -+ } -+ - if (sb->s_op->remount_fs) { - retval = sb->s_op->remount_fs(sb, &flags, data); - if (retval) -@@ -953,6 +962,11 @@ vfs_kern_mount(struct file_system_type * - WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " - "negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes); - -+ error = -EROFS; -+ if (!(flags & MS_RDONLY) && -+ (mnt->mnt_sb->s_readonly_users)) -+ goto out_sb; -+ - mnt->mnt_mountpoint = mnt->mnt_root; - mnt->mnt_parent = mnt; - up_write(&mnt->mnt_sb->s_umount); ---- /dev/null -+++ b/fs/union.c -@@ -0,0 +1,981 @@ -+/* -+ * VFS based union mount for Linux -+ * -+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH. -+ * Copyright (C) 2007-2009 Novell Inc. -+ * -+ * Author(s): Jan Blunck (j.blunck@tu-harburg.de) -+ * Valerie Aurora <vaurora@redhat.com> -+ * -+ * This program is free software; you can redistribute it and/or modify it -+ * under the terms of the GNU General Public License as published by the Free -+ * Software Foundation; either version 2 of the License, or (at your option) -+ * any later version. -+ */ -+ -+#include <linux/bootmem.h> -+#include <linux/init.h> -+#include <linux/module.h> -+#include <linux/types.h> -+#include <linux/hash.h> -+#include <linux/fs.h> -+#include <linux/mount.h> -+#include <linux/fs_struct.h> -+#include <linux/union.h> -+#include <linux/namei.h> -+#include <linux/file.h> -+#include <linux/mm.h> -+#include <linux/quotaops.h> -+#include <linux/dnotify.h> -+#include <linux/security.h> -+#include <linux/pipe_fs_i.h> -+#include <linux/splice.h> -+ -+/* -+ * This is borrowed from fs/inode.c. The hashtable for lookups. Somebody -+ * should try to make this good - I've just made it work. -+ */ -+static unsigned int union_hash_mask __read_mostly; -+static unsigned int union_hash_shift __read_mostly; -+static struct hlist_head *union_hashtable __read_mostly; -+static unsigned int union_rhash_mask __read_mostly; -+static unsigned int union_rhash_shift __read_mostly; -+static struct hlist_head *union_rhashtable __read_mostly; -+ -+/* -+ * Locking Rules: -+ * - dcache_lock (for union_rlookup() only) -+ * - union_lock -+ */ -+DEFINE_SPINLOCK(union_lock); -+ -+static struct kmem_cache *union_cache __read_mostly; -+ -+static unsigned long hash(struct dentry *dentry, struct vfsmount *mnt) -+{ -+ unsigned long tmp; -+ -+ tmp = ((unsigned long)mnt * (unsigned long)dentry) ^ -+ (GOLDEN_RATIO_PRIME + (unsigned long)mnt) / L1_CACHE_BYTES; -+ tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> union_hash_shift); -+ return tmp & union_hash_mask; -+} -+ -+static __initdata unsigned long union_hash_entries; -+ -+static int __init set_union_hash_entries(char *str) -+{ -+ if (!str) -+ return 0; -+ union_hash_entries = simple_strtoul(str, &str, 0); -+ return 1; -+} -+ -+__setup("union_hash_entries=", set_union_hash_entries); -+ -+static int __init init_union(void) -+{ -+ int loop; -+ -+ union_cache = KMEM_CACHE(union_mount, SLAB_PANIC | SLAB_MEM_SPREAD); -+ union_hashtable = alloc_large_system_hash("Union-cache", -+ sizeof(struct hlist_head), -+ union_hash_entries, -+ 14, -+ 0, -+ &union_hash_shift, -+ &union_hash_mask, -+ 0); -+ -+ for (loop = 0; loop < (1 << union_hash_shift); loop++) -+ INIT_HLIST_HEAD(&union_hashtable[loop]); -+ -+ -+ union_rhashtable = alloc_large_system_hash("rUnion-cache", -+ sizeof(struct hlist_head), -+ union_hash_entries, -+ 14, -+ 0, -+ &union_rhash_shift, -+ &union_rhash_mask, -+ 0); -+ -+ for (loop = 0; loop < (1 << union_rhash_shift); loop++) -+ INIT_HLIST_HEAD(&union_rhashtable[loop]); -+ -+ return 0; -+} -+ -+fs_initcall(init_union); -+ -+struct union_mount *union_alloc(struct dentry *this, struct vfsmount *this_mnt, -+ struct dentry *next, struct vfsmount *next_mnt) -+{ -+ struct union_mount *um; -+ -+ BUG_ON(!S_ISDIR(this->d_inode->i_mode)); -+ BUG_ON(!S_ISDIR(next->d_inode->i_mode)); -+ -+ um = kmem_cache_alloc(union_cache, GFP_ATOMIC); -+ if (!um) -+ return NULL; -+ -+ atomic_set(&um->u_count, 1); -+ INIT_LIST_HEAD(&um->u_unions); -+ INIT_LIST_HEAD(&um->u_list); -+ INIT_HLIST_NODE(&um->u_hash); -+ INIT_HLIST_NODE(&um->u_rhash); -+ -+ um->u_this.mnt = this_mnt; -+ um->u_this.dentry = this; -+ um->u_next.mnt = mntget(next_mnt); -+ um->u_next.dentry = dget(next); -+ -+ return um; -+} -+ -+struct union_mount *union_get(struct union_mount *um) -+{ -+ BUG_ON(!atomic_read(&um->u_count)); -+ atomic_inc(&um->u_count); -+ return um; -+} -+ -+static int __union_put(struct union_mount *um) -+{ -+ if (!atomic_dec_and_test(&um->u_count)) -+ return 0; -+ -+ BUG_ON(!hlist_unhashed(&um->u_hash)); -+ BUG_ON(!hlist_unhashed(&um->u_rhash)); -+ -+ kmem_cache_free(union_cache, um); -+ return 1; -+} -+ -+void union_put(struct union_mount *um) -+{ -+ struct path tmp = um->u_next; -+ -+ if (__union_put(um)) -+ path_put(&tmp); -+} -+ -+static void __union_hash(struct union_mount *um) -+{ -+ hlist_add_head(&um->u_hash, union_hashtable + -+ hash(um->u_this.dentry, um->u_this.mnt)); -+ hlist_add_head(&um->u_rhash, union_rhashtable + -+ hash(um->u_next.dentry, um->u_next.mnt)); -+} -+ -+static void __union_unhash(struct union_mount *um) -+{ -+ hlist_del_init(&um->u_hash); -+ hlist_del_init(&um->u_rhash); -+} -+ -+struct union_mount *union_lookup(struct dentry *dentry, struct vfsmount *mnt) -+{ -+ struct hlist_head *head = union_hashtable + hash(dentry, mnt); -+ struct hlist_node *node; -+ struct union_mount *um; -+ -+ hlist_for_each_entry(um, node, head, u_hash) { -+ if ((um->u_this.dentry == dentry) && -+ (um->u_this.mnt == mnt)) -+ return um; -+ } -+ -+ return NULL; -+} -+ -+struct union_mount *union_rlookup(struct dentry *dentry, struct vfsmount *mnt) -+{ -+ struct hlist_head *head = union_rhashtable + hash(dentry, mnt); -+ struct hlist_node *node; -+ struct union_mount *um; -+ -+ hlist_for_each_entry(um, node, head, u_rhash) { -+ if ((um->u_next.dentry == dentry) && -+ (um->u_next.mnt == mnt)) -+ return um; -+ } -+ -+ return NULL; -+} -+ -+/* -+ * is_unionized - check if a dentry lives on a union mounted file system -+ * -+ * This tests if a dentry is living on an union mounted file system by walking -+ * the file system hierarchy. -+ */ -+int is_unionized(struct dentry *dentry, struct vfsmount *mnt) -+{ -+ struct path this = { .mnt = mntget(mnt), -+ .dentry = dget(dentry) }; -+ struct vfsmount *tmp; -+ -+ do { -+ /* check if there is an union mounted on top of us */ -+ spin_lock(&vfsmount_lock); -+ list_for_each_entry(tmp, &this.mnt->mnt_mounts, mnt_child) { -+ if (!(tmp->mnt_flags & MNT_UNION)) -+ continue; -+ /* Isn't this a bug? */ -+ if (this.dentry->d_sb != tmp->mnt_mountpoint->d_sb) -+ continue; -+ if (is_subdir(this.dentry, tmp->mnt_mountpoint)) { -+ spin_unlock(&vfsmount_lock); -+ path_put(&this); -+ return 1; -+ } -+ } -+ spin_unlock(&vfsmount_lock); -+ -+ /* check our mountpoint next */ -+ tmp = mntget(this.mnt->mnt_parent); -+ dput(this.dentry); -+ this.dentry = dget(this.mnt->mnt_mountpoint); -+ mntput(this.mnt); -+ this.mnt = tmp; -+ } while (this.mnt != this.mnt->mnt_parent); -+ -+ path_put(&this); -+ return 0; -+} -+ -+int append_to_union(struct vfsmount *mnt, struct dentry *dentry, -+ struct vfsmount *dest_mnt, struct dentry *dest_dentry) -+{ -+ struct union_mount *this, *um; -+ -+ BUG_ON(!IS_MNT_UNION(mnt)); -+ -+ this = union_alloc(dentry, mnt, dest_dentry, dest_mnt); -+ if (!this) -+ return -ENOMEM; -+ -+ spin_lock(&union_lock); -+ um = union_lookup(dentry, mnt); -+ if (um) { -+ BUG_ON((um->u_next.dentry != dest_dentry) || -+ (um->u_next.mnt != dest_mnt)); -+ spin_unlock(&union_lock); -+ union_put(this); -+ return 0; -+ } -+ list_add(&this->u_list, &mnt->mnt_unions); -+ list_add(&this->u_unions, &dentry->d_unions); -+ dest_dentry->d_unionized++; -+ __union_hash(this); -+ spin_unlock(&union_lock); -+ return 0; -+} -+ -+/* -+ * follow_union_down - follow the union stack one layer down -+ * -+ * This is called to traverse the union stack from one layer to the next -+ * overlayed one. follow_union_down() is called by various lookup functions -+ * that are aware of union mounts. -+ * -+ * Returns non-zero if followed to the next layer, zero otherwise. -+ */ -+int follow_union_down(struct path *path) -+{ -+ struct union_mount *um; -+ -+ if (!IS_MNT_UNION(path->mnt)) -+ return 0; -+ -+ spin_lock(&union_lock); -+ um = union_lookup(path->dentry, path->mnt); -+ spin_unlock(&union_lock); -+ if (um) { -+ path_get(&um->u_next); -+ dput(path->dentry); -+ path->dentry = um->u_next.dentry; -+ mntput(path->mnt); -+ path->mnt = um->u_next.mnt; -+ return 1; -+ } -+ return 0; -+} -+ -+/* -+ * follow_union_mount - follow the union stack to the topmost layer -+ * -+ * This is called to traverse the union stack to the topmost layer. This is -+ * necessary for following parent pointers in an union mount. -+ * -+ * Returns none zero if followed to the topmost layer, zero otherwise. -+ */ -+int follow_union_mount(struct path *path) -+{ -+ struct union_mount *um; -+ int res = 0; -+ -+ while (IS_UNION(path->dentry)) { -+ spin_lock(&dcache_lock); -+ spin_lock(&union_lock); -+ um = union_rlookup(path->dentry, path->mnt); -+ if (um) -+ path_get(&um->u_this); -+ spin_unlock(&union_lock); -+ spin_unlock(&dcache_lock); -+ -+ /* -+ * Q: Aaargh, how do I validate the topmost dentry pointer? -+ * A: Eeeeasy! We took the dcache_lock and union_lock. Since -+ * this protects from any dput'ng going on, we know that the -+ * dentry is valid since the union is unhashed under -+ * dcache_lock too. -+ */ -+ if (!um) -+ break; -+ dput(path->dentry); -+ path->dentry = um->u_this.dentry; -+ mntput(path->mnt); -+ path->mnt = um->u_this.mnt; -+ res = 1; -+ } -+ -+ return res; -+} -+ -+/* -+ * Union mount copyup support -+ */ -+ -+extern int hash_lookup_union(struct nameidata *, struct qstr *, struct path *); -+extern void follow_mount(struct path *); -+ -+/* -+ * union_relookup_topmost - lookup and create the topmost path to dentry -+ * @nd: pointer to nameidata -+ * @flags: lookup flags -+ */ -+static int union_relookup_topmost(struct nameidata *nd, int flags) -+{ -+ int err; -+ char *kbuf, *name; -+ struct nameidata this; -+ -+ kbuf = (char *)__get_free_page(GFP_KERNEL); -+ if (!kbuf) -+ return -ENOMEM; -+ -+ name = d_path(&nd->path, kbuf, PAGE_SIZE); -+ err = PTR_ERR(name); -+ if (IS_ERR(name)) -+ goto free_page; -+ -+ err = path_lookup(name, flags|LOOKUP_CREATE|LOOKUP_TOPMOST, &this); -+ if (err) -+ goto free_page; -+ -+ path_put(&nd->path); -+ nd->path.dentry = this.path.dentry; -+ nd->path.mnt = this.path.mnt; -+ -+ /* -+ * the nd->flags should be unchanged -+ */ -+ BUG_ON(this.um_flags & LAST_LOWLEVEL); -+ nd->um_flags &= ~LAST_LOWLEVEL; -+ free_page: -+ free_page((unsigned long)kbuf); -+ return err; -+} -+ -+static void __update_fs_pwd(struct path *path, struct dentry *dentry, -+ struct vfsmount *mnt) -+{ -+ struct path old = { NULL, NULL }; -+ -+ write_lock(¤t->fs->lock); -+ if (current->fs->pwd.dentry == path->dentry) { -+ old = current->fs->pwd; -+ path_get(¤t->fs->pwd); -+ } -+ write_unlock(¤t->fs->lock); -+ -+ if (old.dentry) -+ path_put(&old); -+ -+ return; -+} -+ -+/** -+ * union_permission - check for access rights to a given inode -+ * @inode: inode to check permission on -+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) -+ * -+ * In a union mount, the top layer is always read-write and the bottom -+ * is always read-only. Ignore the read-only flag on the lower fs. -+ * -+ * Only need for certain activities, like checking to see if write -+ * access is ok. -+ */ -+ -+int union_permission(struct path *path, int mask) -+{ -+ struct inode *inode = path->dentry->d_inode; -+ -+ if (!is_unionized(path->dentry, path->mnt)) -+ return inode_permission(inode, mask); -+ -+ /* Tell __inode_permission to ignore MS_RDONLY */ -+ return __inode_permission(inode, mask, 0); -+} -+ -+/* -+ * union_create_topmost - create the topmost path component -+ * @nd: pointer to nameidata of the base directory -+ * @name: pointer to file name -+ * @path: pointer to path of the overlaid file -+ * -+ * This is called by __link_path_walk() to create the directories on a path -+ * when it is called with LOOKUP_TOPMOST. -+ */ -+struct dentry *union_create_topmost(struct nameidata *nd, struct qstr *name, -+ struct path *path) -+{ -+ struct dentry *dentry, *parent = nd->path.dentry; -+ int res, mode = path->dentry->d_inode->i_mode; -+ -+ if (parent->d_sb == path->dentry->d_sb) -+ return ERR_PTR(-EEXIST); -+ -+ mutex_lock(&parent->d_inode->i_mutex); -+ dentry = lookup_one_len(name->name, nd->path.dentry, name->len); -+ if (IS_ERR(dentry)) -+ goto out_unlock; -+ -+ switch (mode & S_IFMT) { -+ case S_IFREG: -+ /* -+ * FIXME: Does this make any sense in this case? -+ * Special case - lookup gave negative, but... we had foo/bar/ -+ * From the vfs_mknod() POV we just have a negative dentry - -+ * all is fine. Let's be bastards - you had / on the end,you've -+ * been asking for (non-existent) directory. -ENOENT for you. -+ */ -+ if (name->name[name->len] && !dentry->d_inode) { -+ dput(dentry); -+ dentry = ERR_PTR(-ENOENT); -+ goto out_unlock; -+ } -+ -+ res = vfs_create(parent->d_inode, dentry, mode, nd); -+ if (res) { -+ dput(dentry); -+ dentry = ERR_PTR(res); -+ goto out_unlock; -+ } -+ break; -+ case S_IFDIR: -+ res = vfs_mkdir(parent->d_inode, dentry, mode); -+ if (res) { -+ dput(dentry); -+ dentry = ERR_PTR(res); -+ goto out_unlock; -+ } -+ -+ res = append_to_union(nd->path.mnt, dentry, path->mnt, -+ path->dentry); -+ if (res) { -+ dput(dentry); -+ dentry = ERR_PTR(res); -+ goto out_unlock; -+ } -+ break; -+ default: -+ dput(dentry); -+ dentry = ERR_PTR(-EINVAL); -+ goto out_unlock; -+ } -+ -+ /* FIXME: Really necessary ??? */ -+/* __update_fs_pwd(path, dentry, nd->path.mnt); */ -+ -+ out_unlock: -+ mutex_unlock(&parent->d_inode->i_mutex); -+ return dentry; -+} -+ -+static int union_copy_file(struct dentry *old_dentry, struct vfsmount *old_mnt, -+ struct dentry *new_dentry, struct vfsmount *new_mnt) -+{ -+ int ret; -+ size_t size; -+ loff_t offset; -+ struct file *old_file, *new_file; -+ const struct cred *cred = current_cred(); -+ -+ dget(old_dentry); -+ mntget(old_mnt); -+ old_file = dentry_open(old_dentry, old_mnt, O_RDONLY, cred); -+ if (IS_ERR(old_file)) -+ return PTR_ERR(old_file); -+ -+ dget(new_dentry); -+ mntget(new_mnt); -+ new_file = dentry_open(new_dentry, new_mnt, O_WRONLY, cred); -+ ret = PTR_ERR(new_file); -+ if (IS_ERR(new_file)) -+ goto fput_old; -+ -+ /* XXX be smart by using a length param, which indicates max -+ * data we'll want (e.g., we are about to truncate to 0 or 10 -+ * bytes or something */ -+ size = i_size_read(old_file->f_path.dentry->d_inode); -+ if (((size_t)size != size) || ((ssize_t)size != size)) { -+ ret = -EFBIG; -+ goto fput_new; -+ } -+ -+ offset = 0; -+ ret = do_splice_direct(old_file, &offset, new_file, size, -+ SPLICE_F_MOVE); -+ if (ret >= 0) -+ ret = 0; -+ fput_new: -+ fput(new_file); -+ fput_old: -+ fput(old_file); -+ return ret; -+} -+ -+/** -+ * __union_copyup - copy a file to the topmost directory -+ * @old: pointer to path of the old file name -+ * @new_nd: pointer to nameidata of the topmost directory -+ * @new: pointer to path of the new file name -+ * -+ * The topmost directory @new_nd must already be locked. Creates the topmost -+ * file if it doesn't exist yet. -+ */ -+int __union_copyup(struct path *old, struct nameidata *new_nd, -+ struct path *new) -+{ -+ struct dentry *dentry; -+ int error; -+ -+ /* Maybe this should be -EINVAL */ -+ if (S_ISDIR(old->dentry->d_inode->i_mode)) -+ return -EISDIR; -+ -+ if (new_nd->path.dentry != new->dentry->d_parent) { -+ mutex_lock(&new_nd->path.dentry->d_inode->i_mutex); -+ dentry = lookup_one_len(new->dentry->d_name.name, -+ new_nd->path.dentry, -+ new->dentry->d_name.len); -+ mutex_unlock(&new_nd->path.dentry->d_inode->i_mutex); -+ if (IS_ERR(dentry)) -+ return PTR_ERR(dentry); -+ error = -EEXIST; -+ if (dentry->d_inode) -+ goto out_dput; -+ } else -+ dentry = dget(new->dentry); -+ -+ if (!dentry->d_inode) { -+ error = vfs_create(new_nd->path.dentry->d_inode, dentry, -+ old->dentry->d_inode->i_mode, new_nd); -+ if (error) -+ goto out_dput; -+ } -+ -+ BUG_ON(!S_ISREG(old->dentry->d_inode->i_mode)); -+ error = union_copy_file(old->dentry, old->mnt, dentry, -+ new_nd->path.mnt); -+ if (error) { -+ /* FIXME: are there return value we should not -+ * BUG() on ? */ -+ BUG_ON(vfs_unlink(new_nd->path.dentry->d_inode, -+ dentry)); -+ goto out_dput; -+ } -+ -+ dput(new->dentry); -+ new->dentry = dentry; -+ if (new->mnt != new_nd->path.mnt) -+ mntput(new->mnt); -+ new->mnt = new_nd->path.mnt; -+ return error; -+ -+out_dput: -+ dput(dentry); -+ return error; -+} -+ -+/* -+ * union_copyup - copy a file to the topmost layer of the union stack -+ * @nd: nameidata pointer to the file -+ * @flags: flags given to open_namei -+ */ -+int union_copyup(struct nameidata *nd, int flags /* XXX not used */) -+{ -+ struct qstr this; -+ char *name; -+ struct dentry *dir; -+ struct path path; -+ int err; -+ -+ if (!is_unionized(nd->path.dentry, nd->path.mnt)) -+ return 0; -+ if (!S_ISREG(nd->path.dentry->d_inode->i_mode)) -+ return 0; -+ -+ /* safe the name for hash_lookup_union() */ -+ this.len = nd->path.dentry->d_name.len; -+ this.hash = nd->path.dentry->d_name.hash; -+ name = kmalloc(this.len + 1, GFP_KERNEL); -+ if (!name) -+ return -ENOMEM; -+ this.name = name; -+ memcpy(name, nd->path.dentry->d_name.name, nd->path.dentry->d_name.len); -+ name[this.len] = 0; -+ -+ err = union_relookup_topmost(nd, nd->flags|LOOKUP_PARENT); -+ if (err) { -+ kfree(name); -+ return err; -+ } -+ nd->flags &= ~LOOKUP_PARENT; -+ -+ dir = nd->path.dentry; -+ mutex_lock(&dir->d_inode->i_mutex); -+ err = hash_lookup_union(nd, &this, &path); -+ mutex_unlock(&dir->d_inode->i_mutex); -+ kfree(name); -+ if (err) -+ return err; -+ -+ err = -ENOENT; -+ if (!path.dentry->d_inode) -+ goto exit_dput; -+ -+ /* Necessary?! I guess not ... */ -+ follow_mount(&path); -+ -+ err = -ENOENT; -+ if (!path.dentry->d_inode) -+ goto exit_dput; -+ -+ err = -EISDIR; -+ if (!S_ISREG(path.dentry->d_inode->i_mode)) -+ goto exit_dput; -+ -+ if (path.dentry->d_parent != nd->path.dentry) { -+ err = __union_copyup(&path, nd, &path); -+ if (err) -+ goto exit_dput; -+ } -+ -+ dput(nd->path.dentry); -+ if (nd->path.mnt != path.mnt) -+ mntput(nd->path.mnt); -+ nd->path = path; -+ return 0; -+ -+exit_dput: -+ dput(path.dentry); -+ if (path.mnt != nd->path.mnt) -+ mntput(path.mnt); -+ return err; -+} -+ -+/* -+ * This must be called when unhashing a dentry. This is called with dcache_lock -+ * and unhashes all unions this dentry is in. -+ */ -+void __d_drop_unions(struct dentry *dentry) -+{ -+ struct union_mount *this, *next; -+ -+ spin_lock(&union_lock); -+ list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) -+ __union_unhash(this); -+ spin_unlock(&union_lock); -+} -+EXPORT_SYMBOL_GPL(__d_drop_unions); -+ -+/* -+ * This must be called after __d_drop_unions() without holding any locks. -+ * Note: The dentry might still be reachable via a lookup but at that time it -+ * already a negative dentry. Otherwise it would be unhashed. The union_mount -+ * structure itself is still reachable through mnt->mnt_unions (which we -+ * protect against with union_lock). -+ */ -+void shrink_d_unions(struct dentry *dentry) -+{ -+ struct union_mount *this, *next; -+ -+repeat: -+ spin_lock(&union_lock); -+ list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) { -+ BUG_ON(!hlist_unhashed(&this->u_hash)); -+ BUG_ON(!hlist_unhashed(&this->u_rhash)); -+ list_del(&this->u_list); -+ list_del(&this->u_unions); -+ this->u_next.dentry->d_unionized--; -+ spin_unlock(&union_lock); -+ union_put(this); -+ goto repeat; -+ } -+ spin_unlock(&union_lock); -+} -+ -+extern void __dput(struct dentry *, struct list_head *, int); -+ -+/* -+ * This is the special variant for use in dput() only. -+ */ -+void __shrink_d_unions(struct dentry *dentry, struct list_head *list) -+{ -+ struct union_mount *this, *next; -+ -+ BUG_ON(!d_unhashed(dentry)); -+ -+repeat: -+ spin_lock(&union_lock); -+ list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) { -+ struct dentry *n_dentry = this->u_next.dentry; -+ struct vfsmount *n_mnt = this->u_next.mnt; -+ -+ BUG_ON(!hlist_unhashed(&this->u_hash)); -+ BUG_ON(!hlist_unhashed(&this->u_rhash)); -+ list_del(&this->u_list); -+ list_del(&this->u_unions); -+ this->u_next.dentry->d_unionized--; -+ spin_unlock(&union_lock); -+ if (__union_put(this)) { -+ __dput(n_dentry, list, 0); -+ mntput(n_mnt); -+ } -+ goto repeat; -+ } -+ spin_unlock(&union_lock); -+} -+ -+/* -+ * Remove all union_mounts structures belonging to this vfsmount from the -+ * union lookup hashtable and so on ... -+ */ -+void shrink_mnt_unions(struct vfsmount *mnt) -+{ -+ struct union_mount *this, *next; -+ -+repeat: -+ spin_lock(&union_lock); -+ list_for_each_entry_safe(this, next, &mnt->mnt_unions, u_list) { -+ if (this->u_this.dentry == mnt->mnt_root) -+ continue; -+ __union_unhash(this); -+ list_del(&this->u_list); -+ list_del(&this->u_unions); -+ this->u_next.dentry->d_unionized--; -+ spin_unlock(&union_lock); -+ union_put(this); -+ goto repeat; -+ } -+ spin_unlock(&union_lock); -+} -+ -+int attach_mnt_union(struct vfsmount *mnt, struct vfsmount *dest_mnt, -+ struct dentry *dest_dentry) -+{ -+ if (!IS_MNT_UNION(mnt)) -+ return 0; -+ -+ return append_to_union(mnt, mnt->mnt_root, dest_mnt, dest_dentry); -+} -+ -+void detach_mnt_union(struct vfsmount *mnt) -+{ -+ struct union_mount *um; -+ -+ if (!IS_MNT_UNION(mnt)) -+ return; -+ -+ shrink_mnt_unions(mnt); -+ -+ spin_lock(&union_lock); -+ um = union_lookup(mnt->mnt_root, mnt); -+ __union_unhash(um); -+ list_del(&um->u_list); -+ list_del(&um->u_unions); -+ um->u_next.dentry->d_unionized--; -+ spin_unlock(&union_lock); -+ union_put(um); -+ return; -+} -+ -+/** -+ * union_copyup_dir_one - copy up a single directory entry -+ * -+ * Individual directory entry copyup function for union_copyup_dir. -+ * We get the entries from higher level layers first. -+ */ -+ -+static int union_copyup_dir_one(void *buf, const char *name, int namlen, -+ loff_t offset, u64 ino, unsigned int d_type) -+{ -+ struct dentry *topmost_dentry = (struct dentry *) buf; -+ struct dentry *dentry; -+ int err = 0; -+ -+ switch (namlen) { -+ case 2: -+ if (name[1] != '.') -+ break; -+ case 1: -+ if (name[0] != '.') -+ break; -+ return 0; -+ } -+ -+ /* Lookup this entry in the topmost directory */ -+ dentry = lookup_one_len(name, topmost_dentry, namlen); -+ -+ if (IS_ERR(dentry)) { -+ printk(KERN_INFO "error looking up %s\n", dentry->d_name.name); -+ goto out; -+ } -+ -+ /* -+ * If the entry already exists, one of the following is true: -+ * it was already copied up (due to an earlier lookup), an -+ * entry with the same name already exists on the topmost file -+ * system, it is a whiteout, or it is a fallthru. In each -+ * case, the top level entry masks any entries from lower file -+ * systems, so don't copy up this entry. -+ */ -+ if (dentry->d_inode || d_is_whiteout(dentry) || -+ d_is_fallthru(dentry)) { -+ printk(KERN_INFO "skipping copy of %s\n", dentry->d_name.name); -+ goto out_dput; -+ } -+ -+ /* -+ * If the entry doesn't exist, create a fallthru entry in the -+ * topmost file system. All possible directory types are -+ * used, so each file system must implement its own way of -+ * storing a fallthru entry. -+ */ -+ printk(KERN_INFO "creating fallthru for %s\n", dentry->d_name.name); -+ err = topmost_dentry->d_inode->i_op->fallthru(topmost_dentry->d_inode, -+ dentry); -+ /* FIXME */ -+ BUG_ON(err); -+ /* -+ * At this point, we have a negative dentry marked as fallthru -+ * in the cache. We could potentially lookup the entry lower -+ * level file system and turn this into a positive dentry -+ * right now, but it is not clear that would be a performance -+ * win and adds more opportunities to fail. -+ */ -+out_dput: -+ dput(dentry); -+out: -+ return 0; -+} -+ -+/** -+ * union_copyup_dir - copy up low-level directory entries to topmost dir -+ * -+ * readdir() is difficult to support on union file systems for two -+ * reasons: We must eliminate duplicates and apply whiteouts, and we -+ * must return something in f_pos that lets us restart in the same -+ * place when we return. Our solution is to, on first readdir() of -+ * the directory, copy up all visible entries from the low-level file -+ * systems and mark the entries that refer to low-level file system -+ * objects as "fallthru" entries. -+ */ -+ -+int union_copyup_dir(struct path *topmost_path) -+{ -+ struct dentry *topmost_dentry = topmost_path->dentry; -+ struct path path = *topmost_path; -+ int res = 0; -+ -+ /* -+ * Skip opaque dirs. -+ */ -+ if (IS_OPAQUE(topmost_dentry->d_inode)) -+ return 0; -+ -+ /* -+ * Mark this dir opaque to show that we have already copied up -+ * the lower entries. Only fallthru entries pass through to -+ * the underlying file system. -+ * -+ * XXX Deal with the lower file system changing. This could -+ * be through running a tool over the top level file system to -+ * make directories transparent again, or we could check the -+ * mtime of the underlying directory. -+ */ -+ -+ topmost_dentry->d_inode->i_flags |= S_OPAQUE; -+ mark_inode_dirty(topmost_dentry->d_inode); -+ -+ /* -+ * Loop through each dir on each level copying up the entries -+ * to the topmost. -+ */ -+ -+ /* Don't drop the caller's reference to the topmost path */ -+ path_get(&path); -+ while (follow_union_down(&path)) { -+ struct file * ftmp; -+ struct inode * inode; -+ -+ /* XXX Permit fallthrus on lower-level? Would need to -+ * pass in opaque flag to union_copyup_dir_one() and -+ * only copy up fallthru entries there. We allow -+ * fallthrus in lower level opaque directories on -+ * lookup, so for consistency we should do one or the -+ * other in both places. */ -+ if (IS_OPAQUE(path.dentry->d_inode)) -+ break; -+ -+ /* dentry_open() doesn't get a path reference itself */ -+ path_get(&path); -+ ftmp = dentry_open(path.dentry, path.mnt, -+ O_RDONLY | O_DIRECTORY | O_NOATIME, -+ current_cred()); -+ if (IS_ERR(ftmp)) { -+ printk (KERN_ERR "unable to open dir %s for " -+ "directory copyup: %ld\n", -+ path.dentry->d_name.name, PTR_ERR(ftmp)); -+ continue; -+ } -+ -+ inode = path.dentry->d_inode; -+ mutex_lock(&inode->i_mutex); -+ -+ res = -ENOENT; -+ if (IS_DEADDIR(inode)) -+ goto out_fput; -+ /* -+ * Read the whole directory, calling our directory -+ * entry copyup function on each entry. Pass in the -+ * topmost dentry as our private data so we can create -+ * new entries in the topmost directory. -+ */ -+ res = ftmp->f_op->readdir(ftmp, topmost_dentry, -+ union_copyup_dir_one); -+out_fput: -+ mutex_unlock(&inode->i_mutex); -+ fput(ftmp); -+ -+ if (res) -+ break; -+ } -+ path_put(&path); -+ return res; -+} ---- a/include/linux/dcache.h -+++ b/include/linux/dcache.h -@@ -101,6 +101,15 @@ struct dentry { - struct dentry *d_parent; /* parent directory */ - struct qstr d_name; - -+#ifdef CONFIG_UNION_MOUNT -+ /* -+ * The following fields are used by the VFS based union mount -+ * implementation. Both are protected by union_lock! -+ */ -+ struct list_head d_unions; /* list of union_mount's */ -+ unsigned int d_unionized; /* unions referencing this dentry */ -+#endif -+ - struct list_head d_lru; /* LRU list */ - /* - * d_child and d_rcu can share memory -@@ -186,6 +195,9 @@ d_iput: no no no yes - - #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */ - -+#define DCACHE_WHITEOUT 0x0100 /* This negative dentry is a whiteout */ -+#define DCACHE_FALLTHRU 0x0200 /* Keep looking in the file system below */ -+ - extern spinlock_t dcache_lock; - extern seqlock_t rename_lock; - -@@ -205,12 +217,20 @@ extern seqlock_t rename_lock; - * __d_drop requires dentry->d_lock. - */ - -+#ifdef CONFIG_UNION_MOUNT -+extern void __d_drop_unions(struct dentry *); -+#endif -+ - static inline void __d_drop(struct dentry *dentry) - { - if (!(dentry->d_flags & DCACHE_UNHASHED)) { - dentry->d_flags |= DCACHE_UNHASHED; - hlist_del_rcu(&dentry->d_hash); - } -+#ifdef CONFIG_UNION_MOUNT -+ /* remove dentry from the union hashtable */ -+ __d_drop_unions(dentry); -+#endif - } - - static inline void d_drop(struct dentry *dentry) -@@ -358,6 +378,16 @@ static inline int d_unlinked(struct dent - return d_unhashed(dentry) && !IS_ROOT(dentry); - } - -+static inline int d_is_whiteout(struct dentry *dentry) -+{ -+ return (dentry->d_flags & DCACHE_WHITEOUT); -+} -+ -+static inline int d_is_fallthru(struct dentry *dentry) -+{ -+ return (dentry->d_flags & DCACHE_FALLTHRU); -+} -+ - static inline struct dentry *dget_parent(struct dentry *dentry) - { - struct dentry *ret; ---- a/include/linux/ext2_fs.h -+++ b/include/linux/ext2_fs.h -@@ -189,6 +189,7 @@ struct ext2_group_desc - #define EXT2_NOTAIL_FL FS_NOTAIL_FL /* file tail should not be merged */ - #define EXT2_DIRSYNC_FL FS_DIRSYNC_FL /* dirsync behaviour (directories only) */ - #define EXT2_TOPDIR_FL FS_TOPDIR_FL /* Top of directory hierarchies*/ -+#define EXT2_OPAQUE_FL 0x00040000 - #define EXT2_RESERVED_FL FS_RESERVED_FL /* reserved for ext2 lib */ - - #define EXT2_FL_USER_VISIBLE FS_FL_USER_VISIBLE /* User visible flags */ -@@ -503,10 +504,12 @@ struct ext2_super_block { - #define EXT3_FEATURE_INCOMPAT_RECOVER 0x0004 - #define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV 0x0008 - #define EXT2_FEATURE_INCOMPAT_META_BG 0x0010 -+#define EXT2_FEATURE_INCOMPAT_WHITEOUT 0x0020 - #define EXT2_FEATURE_INCOMPAT_ANY 0xffffffff - - #define EXT2_FEATURE_COMPAT_SUPP EXT2_FEATURE_COMPAT_EXT_ATTR - #define EXT2_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE| \ -+ EXT2_FEATURE_INCOMPAT_WHITEOUT| \ - EXT2_FEATURE_INCOMPAT_META_BG) - #define EXT2_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \ - EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \ -@@ -573,6 +576,8 @@ enum { - EXT2_FT_FIFO, - EXT2_FT_SOCK, - EXT2_FT_SYMLINK, -+ EXT2_FT_WHT, -+ EXT2_FT_FALLTHRU, - EXT2_FT_MAX - }; - ---- a/include/linux/fs.h -+++ b/include/linux/fs.h -@@ -188,6 +188,7 @@ struct inodes_stat_t { - #define MS_REMOUNT 32 /* Alter flags of a mounted FS */ - #define MS_MANDLOCK 64 /* Allow mandatory locks on an FS */ - #define MS_DIRSYNC 128 /* Directory modifications are synchronous */ -+#define MS_UNION 256 - #define MS_NOATIME 1024 /* Do not update access times. */ - #define MS_NODIRATIME 2048 /* Do not update directory access times */ - #define MS_BIND 4096 -@@ -205,6 +206,7 @@ struct inodes_stat_t { - #define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */ - #define MS_I_VERSION (1<<23) /* Update inode I_version field */ - #define MS_STRICTATIME (1<<24) /* Always perform atime updates */ -+#define MS_WHITEOUT (1<<26) /* fs does support white-out filetype */ - #define MS_ACTIVE (1<<30) - #define MS_NOUSER (1<<31) - -@@ -231,6 +233,7 @@ struct inodes_stat_t { - #define S_NOCMTIME 128 /* Do not update file c/mtime */ - #define S_SWAPFILE 256 /* Do not truncate: swapon got its bmaps */ - #define S_PRIVATE 512 /* Inode is fs-internal */ -+#define S_OPAQUE 1024 /* Directory is opaque */ - - /* - * Note that nosuid etc flags are inode-specific: setting some file-system -@@ -266,6 +269,8 @@ struct inodes_stat_t { - #define IS_SWAPFILE(inode) ((inode)->i_flags & S_SWAPFILE) - #define IS_PRIVATE(inode) ((inode)->i_flags & S_PRIVATE) - -+#define IS_OPAQUE(inode) ((inode)->i_flags & S_OPAQUE) -+ - /* the read-only stuff doesn't really belong here, but any other place is - probably as bad and I don't want to create yet another include file. */ - -@@ -1380,6 +1385,11 @@ struct super_block { - * generic_show_options() - */ - char *s_options; -+ -+ /* -+ * Users who require read-only access - e.g., union mounts -+ */ -+ int s_readonly_users; - }; - - extern struct timespec current_fs_time(struct super_block *sb); -@@ -1517,6 +1527,8 @@ struct inode_operations { - int (*mkdir) (struct inode *,struct dentry *,int); - int (*rmdir) (struct inode *,struct dentry *); - int (*mknod) (struct inode *,struct dentry *,int,dev_t); -+ int (*whiteout) (struct inode *, struct dentry *, struct dentry *); -+ int (*fallthru) (struct inode *, struct dentry *); - int (*rename) (struct inode *, struct dentry *, - struct inode *, struct dentry *); - int (*readlink) (struct dentry *, char __user *,int); -@@ -2108,6 +2120,7 @@ extern void emergency_remount(void); - extern sector_t bmap(struct inode *, sector_t); - #endif - extern int notify_change(struct dentry *, struct iattr *); -+extern int __inode_permission(struct inode *inode, int mask, int rofs); - extern int inode_permission(struct inode *, int); - extern int generic_permission(struct inode *, int, - int (*check_acl)(struct inode *, int)); -@@ -2135,7 +2148,7 @@ extern void free_write_pipe(struct file - - extern struct file *do_filp_open(int dfd, const char *pathname, - int open_flag, int mode, int acc_mode); --extern int may_open(struct path *, int, int); -+extern int may_open(struct nameidata *, int, int); - - extern int kernel_read(struct file *, loff_t, char *, unsigned long); - extern struct file * open_exec(const char *); ---- a/include/linux/mount.h -+++ b/include/linux/mount.h -@@ -35,6 +35,7 @@ struct mnt_namespace; - #define MNT_SHARED 0x1000 /* if the vfsmount is a shared mount */ - #define MNT_UNBINDABLE 0x2000 /* if the vfsmount is a unbindable mount */ - #define MNT_PNODE_MASK 0x3000 /* propagation flag mask */ -+#define MNT_UNION 0x4000 /* if the vfsmount is a union mount */ - - struct vfsmount { - struct list_head mnt_hash; -@@ -53,6 +54,9 @@ struct vfsmount { - struct list_head mnt_slave_list;/* list of slave mounts */ - struct list_head mnt_slave; /* slave list entry */ - struct vfsmount *mnt_master; /* slave is on master->mnt_slave_list */ -+#ifdef CONFIG_UNION_MOUNT -+ struct list_head mnt_unions; /* list of union_mount structures */ -+#endif - struct mnt_namespace *mnt_ns; /* containing namespace */ - int mnt_id; /* mount identifier */ - int mnt_group_id; /* peer group identifier */ ---- a/include/linux/namei.h -+++ b/include/linux/namei.h -@@ -20,6 +20,7 @@ struct nameidata { - struct qstr last; - struct path root; - unsigned int flags; -+ unsigned int um_flags; - int last_type; - unsigned depth; - char *saved_names[MAX_NESTED_LINKS + 1]; -@@ -35,6 +36,9 @@ struct nameidata { - */ - enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; - -+#define LAST_UNION 0x01 -+#define LAST_LOWLEVEL 0x02 -+ - /* - * The bitmask for a lookup event: - * - follow links at the end -@@ -49,6 +53,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA - #define LOOKUP_CONTINUE 4 - #define LOOKUP_PARENT 16 - #define LOOKUP_REVAL 64 -+#define LOOKUP_TOPMOST 128 -+ - /* - * Intent data - */ ---- /dev/null -+++ b/include/linux/union.h -@@ -0,0 +1,84 @@ -+/* -+ * VFS based union mount for Linux -+ * -+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH. -+ * Copyright (C) 2007 Novell Inc. -+ * Author(s): Jan Blunck (j.blunck@tu-harburg.de) -+ * -+ * This program is free software; you can redistribute it and/or modify it -+ * under the terms of the GNU General Public License as published by the Free -+ * Software Foundation; either version 2 of the License, or (at your option) -+ * any later version. -+ * -+ */ -+#ifndef __LINUX_UNION_H -+#define __LINUX_UNION_H -+#ifdef __KERNEL__ -+ -+#include <linux/list.h> -+#include <asm/atomic.h> -+ -+struct dentry; -+struct vfsmount; -+ -+#ifdef CONFIG_UNION_MOUNT -+ -+/* -+ * The new union mount structure. -+ */ -+struct union_mount { -+ atomic_t u_count; /* reference count */ -+ struct mutex u_mutex; -+ struct list_head u_unions; /* list head for d_unions */ -+ struct list_head u_list; /* list head for mnt_unions */ -+ struct hlist_node u_hash; /* list head for seaching */ -+ struct hlist_node u_rhash; /* list head for reverse seaching */ -+ -+ struct path u_this; /* this is me */ -+ struct path u_next; /* this is what I overlay */ -+}; -+ -+#define IS_UNION(dentry) (!list_empty(&(dentry)->d_unions) || \ -+ (dentry)->d_unionized) -+#define IS_MNT_UNION(mnt) ((mnt)->mnt_flags & MNT_UNION) -+ -+extern int is_unionized(struct dentry *, struct vfsmount *); -+extern int append_to_union(struct vfsmount *, struct dentry *, -+ struct vfsmount *, struct dentry *); -+extern int follow_union_down(struct path *); -+extern int follow_union_mount(struct path *); -+extern void __d_drop_unions(struct dentry *); -+extern void shrink_d_unions(struct dentry *); -+extern void __shrink_d_unions(struct dentry *, struct list_head *); -+extern int attach_mnt_union(struct vfsmount *, struct vfsmount *, -+ struct dentry *); -+extern void detach_mnt_union(struct vfsmount *); -+extern struct dentry *union_create_topmost(struct nameidata *, struct qstr *, -+ struct path *); -+extern int __union_copyup(struct path *, struct nameidata *, struct path *); -+extern int union_copyup(struct nameidata *, int); -+extern int union_copyup_dir(struct path *path); -+extern int union_permission(struct path *, int); -+ -+#else /* CONFIG_UNION_MOUNT */ -+ -+#define IS_UNION(x) (0) -+#define IS_MNT_UNION(x) (0) -+#define is_unionized(x, y) (0) -+#define append_to_union(x1, y1, x2, y2) ({ BUG(); (0); }) -+#define follow_union_down(x) ({ (0); }) -+#define follow_union_mount(x) ({ (0); }) -+#define __d_drop_unions(x) do { } while (0) -+#define shrink_d_unions(x) do { } while (0) -+#define __shrink_d_unions(x,y) do { } while (0) -+#define attach_mnt_union(x, y, z) do { } while (0) -+#define detach_mnt_union(x) do { } while (0) -+#define union_create_topmost(x, y, z) ({ BUG(); (NULL); }) -+#define __union_copyup(x, y, z) ({ BUG(); (0); }) -+#define union_copyup(x, y) ({ (0); }) -+#define union_copyup_dir(x) ({ BUG(); (0); }) -+#define union_permission(x, y) inode_permission(x->dentry->d_inode, y) -+ -+#endif /* CONFIG_UNION_MOUNT */ -+#endif /* __KERNEL__ */ -+#endif /* __LINUX_UNION_H */ ---- a/mm/shmem.c -+++ b/mm/shmem.c -@@ -1798,6 +1798,118 @@ static int shmem_statfs(struct dentry *d - return 0; - } - -+static int shmem_rmdir(struct inode *dir, struct dentry *dentry); -+static int shmem_unlink(struct inode *dir, struct dentry *dentry); -+ -+/* -+ * Create a dentry to signify a whiteout. -+ */ -+static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry, -+ struct dentry *new_dentry) -+{ -+ struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb); -+ struct dentry *dentry; -+ -+ if (!(dir->i_sb->s_flags & MS_WHITEOUT)) -+ return -EPERM; -+ -+ /* This gives us a proper initialized negative dentry */ -+ dentry = simple_lookup(dir, new_dentry, NULL); -+ if (dentry && IS_ERR(dentry)) -+ return PTR_ERR(dentry); -+ -+ /* -+ * No ordinary (disk based) filesystem counts whiteouts as inodes; -+ * but each new link needs a new dentry, pinning lowmem, and -+ * tmpfs dentries cannot be pruned until they are unlinked. -+ */ -+ if (sbinfo->max_inodes) { -+ spin_lock(&sbinfo->stat_lock); -+ if (!sbinfo->free_inodes) { -+ spin_unlock(&sbinfo->stat_lock); -+ return -ENOSPC; -+ } -+ sbinfo->free_inodes--; -+ spin_unlock(&sbinfo->stat_lock); -+ } -+ -+ if (old_dentry->d_inode || d_is_fallthru(old_dentry)) { -+ if (old_dentry->d_inode && S_ISDIR(old_dentry->d_inode->i_mode)) -+ shmem_rmdir(dir, old_dentry); -+ else -+ shmem_unlink(dir, old_dentry); -+ } -+ -+ dir->i_size += BOGO_DIRENT_SIZE; -+ dir->i_ctime = dir->i_mtime = CURRENT_TIME; -+ /* Extra pinning count for the created dentry */ -+ dget(new_dentry); -+ spin_lock(&new_dentry->d_lock); -+ new_dentry->d_flags |= DCACHE_WHITEOUT; -+ spin_unlock(&new_dentry->d_lock); -+ return 0; -+} -+ -+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry, -+ struct inode *inode); -+ -+/* -+ * Create a dentry to signify a fallthru. A fallthru lets us read the -+ * low-level dentries into the dcache once on the first readdir() and -+ * then -+ */ -+static int shmem_fallthru(struct inode *dir, struct dentry *dentry) -+{ -+ struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb); -+ -+ /* FIXME: this is stupid */ -+ if (!(dir->i_sb->s_flags & MS_WHITEOUT)) -+ return -EPERM; -+ -+ if (dentry->d_inode || d_is_fallthru(dentry) || d_is_whiteout(dentry)) -+ return -EEXIST; -+ -+ /* -+ * Each new link needs a new dentry, pinning lowmem, and tmpfs -+ * dentries cannot be pruned until they are unlinked. -+ */ -+ if (sbinfo->max_inodes) { -+ spin_lock(&sbinfo->stat_lock); -+ if (!sbinfo->free_inodes) { -+ spin_unlock(&sbinfo->stat_lock); -+ return -ENOSPC; -+ } -+ sbinfo->free_inodes--; -+ spin_unlock(&sbinfo->stat_lock); -+ } -+ -+ shmem_d_instantiate(dir, dentry, NULL); -+ dir->i_ctime = dir->i_mtime = CURRENT_TIME; -+ -+ spin_lock(&dentry->d_lock); -+ dentry->d_flags |= DCACHE_FALLTHRU; -+ spin_unlock(&dentry->d_lock); -+ return 0; -+} -+ -+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry, -+ struct inode *inode) -+{ -+ if (d_is_whiteout(dentry)) { -+ /* Re-using an existing whiteout */ -+ shmem_free_inode(dir->i_sb); -+ if (S_ISDIR(inode->i_mode)) -+ inode->i_mode |= S_OPAQUE; -+ } else if (d_is_fallthru(dentry)) { -+ shmem_free_inode(dir->i_sb); -+ } else { -+ /* New dentry */ -+ dir->i_size += BOGO_DIRENT_SIZE; -+ dget(dentry); /* Extra count - pin the dentry in core */ -+ } -+ /* Will clear DCACHE_WHITEOUT and DCACHE_FALLTHRU flags */ -+ d_instantiate(dentry, inode); -+} - /* - * File creation. Allocate an inode, and we're done.. - */ -@@ -1822,15 +1934,16 @@ shmem_mknod(struct inode *dir, struct de - iput(inode); - return error; - } -+ - if (dir->i_mode & S_ISGID) { - inode->i_gid = dir->i_gid; - if (S_ISDIR(mode)) - inode->i_mode |= S_ISGID; - } -- dir->i_size += BOGO_DIRENT_SIZE; -+ -+ shmem_d_instantiate(dir, dentry, inode); -+ - dir->i_ctime = dir->i_mtime = CURRENT_TIME; -- d_instantiate(dentry, inode); -- dget(dentry); /* Extra count - pin the dentry in core */ - } - return error; - } -@@ -1868,12 +1981,11 @@ static int shmem_link(struct dentry *old - if (ret) - goto out; - -- dir->i_size += BOGO_DIRENT_SIZE; -+ shmem_d_instantiate(dir, dentry, inode); -+ - inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; - inc_nlink(inode); - atomic_inc(&inode->i_count); /* New dentry reference */ -- dget(dentry); /* Extra pinning count for the created dentry */ -- d_instantiate(dentry, inode); - out: - return ret; - } -@@ -1882,21 +1994,63 @@ static int shmem_unlink(struct inode *di - { - struct inode *inode = dentry->d_inode; - -- if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) -- shmem_free_inode(inode->i_sb); -+ if (d_is_whiteout(dentry) || d_is_fallthru(dentry) || -+ (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))) -+ shmem_free_inode(dir->i_sb); - -+ if (inode) { -+ inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; -+ drop_nlink(inode); -+ } - dir->i_size -= BOGO_DIRENT_SIZE; -- inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; -- drop_nlink(inode); - dput(dentry); /* Undo the count from "create" - this does all the work */ - return 0; - } - -+static void shmem_dir_unlink_whiteouts(struct inode *dir, struct dentry *dentry) -+{ -+ if (!dentry->d_inode) -+ return; -+ -+ /* Remove whiteouts from logical empty directory */ -+ if (S_ISDIR(dentry->d_inode->i_mode) && -+ dentry->d_inode->i_sb->s_flags & MS_WHITEOUT) { -+ struct dentry *child, *next; -+ LIST_HEAD(list); -+ -+ spin_lock(&dcache_lock); -+ list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) { -+ spin_lock(&child->d_lock); -+ /* Unlink fallthrus too */ -+ if (d_is_whiteout(child) || d_is_fallthru(child)) { -+ __d_drop(child); -+ if (!list_empty(&child->d_lru)) { -+ list_del(&child->d_lru); -+ dentry_stat.nr_unused--; -+ } -+ list_add(&child->d_lru, &list); -+ } -+ spin_unlock(&child->d_lock); -+ } -+ spin_unlock(&dcache_lock); -+ -+ list_for_each_entry_safe(child, next, &list, d_lru) { -+ spin_lock(&child->d_lock); -+ list_del_init(&child->d_lru); -+ spin_unlock(&child->d_lock); -+ -+ shmem_unlink(dentry->d_inode, child); -+ } -+ } -+} -+ - static int shmem_rmdir(struct inode *dir, struct dentry *dentry) - { - if (!simple_empty(dentry)) - return -ENOTEMPTY; - -+ /* Remove whiteouts from logical empty directory */ -+ shmem_dir_unlink_whiteouts(dir, dentry); - drop_nlink(dentry->d_inode); - drop_nlink(dir); - return shmem_unlink(dir, dentry); -@@ -1905,7 +2059,7 @@ static int shmem_rmdir(struct inode *dir - /* - * The VFS layer already does all the dentry stuff for rename, - * we just have to decrement the usage count for the target if -- * it exists so that the VFS layer correctly free's it when it -+ * it exists so that the VFS layer correctly frees it when it - * gets overwritten. - */ - static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) -@@ -1916,7 +2070,12 @@ static int shmem_rename(struct inode *ol - if (!simple_empty(new_dentry)) - return -ENOTEMPTY; - -+ if (d_is_whiteout(new_dentry)) -+ shmem_unlink(new_dir, new_dentry); -+ - if (new_dentry->d_inode) { -+ /* Remove whiteouts from logical empty directory */ -+ shmem_dir_unlink_whiteouts(new_dir, new_dentry); - (void) shmem_unlink(new_dir, new_dentry); - if (they_are_dirs) - drop_nlink(old_dir); -@@ -1981,12 +2140,12 @@ static int shmem_symlink(struct inode *d - unlock_page(page); - page_cache_release(page); - } -+ -+ shmem_d_instantiate(dir, dentry, inode); -+ - if (dir->i_mode & S_ISGID) - inode->i_gid = dir->i_gid; -- dir->i_size += BOGO_DIRENT_SIZE; - dir->i_ctime = dir->i_mtime = CURRENT_TIME; -- d_instantiate(dentry, inode); -- dget(dentry); - return 0; - } - -@@ -2363,6 +2522,12 @@ int shmem_fill_super(struct super_block - if (!root) - goto failed_iput; - sb->s_root = root; -+ -+#ifdef CONFIG_TMPFS -+ if (!(sb->s_flags & MS_NOUSER)) -+ sb->s_flags |= MS_WHITEOUT; -+#endif -+ - return 0; - - failed_iput: -@@ -2463,6 +2628,8 @@ static const struct inode_operations shm - .rmdir = shmem_rmdir, - .mknod = shmem_mknod, - .rename = shmem_rename, -+ .whiteout = shmem_whiteout, -+ .fallthru = shmem_fallthru, - #endif - #ifdef CONFIG_TMPFS_POSIX_ACL - .setattr = shmem_notify_change, |