initial_commit

2 files changed, 503 insertions, 0 deletions

diff --git a/fs/exportfs/Makefile b/fs/exportfs/Makefile
new file mode 100644
index 00000000..d7c5d4dd
--- /dev/null
+++ b/fs/exportfs/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for the filesystem export support routines.
+
+obj-$(CONFIG_EXPORTFS) += exportfs.o
+
+exportfs-objs := expfs.o
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
new file mode 100644
index 00000000..b05acb79
--- /dev/null
+++ b/fs/exportfs/expfs.c
@@ -0,0 +1,497 @@
+/*
+ * Copyright (C) Neil Brown 2002
+ * Copyright (C) Christoph Hellwig 2007
+ *
+ * This file contains the code mapping from inodes to NFS file handles,
+ * and for mapping back from file handles to dentries.
+ *
+ * For details on why we do all the strange and hairy things in here
+ * take a look at Documentation/filesystems/nfs/Exporting.
+ */
+#include <linux/exportfs.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/sched.h>
+
+#define dprintk(fmt, args...) do{}while(0)
+
+
+static int get_name(struct vfsmount *mnt, struct dentry *dentry, char *name,
+		struct dentry *child);
+
+
+static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
+		char *name, struct dentry *child)
+{
+	const struct export_operations *nop = dir->d_sb->s_export_op;
+
+	if (nop->get_name)
+		return nop->get_name(dir, name, child);
+	else
+		return get_name(mnt, dir, name, child);
+}
+
+/*
+ * Check if the dentry or any of it's aliases is acceptable.
+ */
+static struct dentry *
+find_acceptable_alias(struct dentry *result,
+		int (*acceptable)(void *context, struct dentry *dentry),
+		void *context)
+{
+	struct dentry *dentry, *toput = NULL;
+	struct inode *inode;
+
+	if (acceptable(context, result))
+		return result;
+
+	inode = result->d_inode;
+	spin_lock(&inode->i_lock);
+	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+		dget(dentry);
+		spin_unlock(&inode->i_lock);
+		if (toput)
+			dput(toput);
+		if (dentry != result && acceptable(context, dentry)) {
+			dput(result);
+			return dentry;
+		}
+		spin_lock(&inode->i_lock);
+		toput = dentry;
+	}
+	spin_unlock(&inode->i_lock);
+
+	if (toput)
+		dput(toput);
+	return NULL;
+}
+
+/*
+ * Find root of a disconnected subtree and return a reference to it.
+ */
+static struct dentry *
+find_disconnected_root(struct dentry *dentry)
+{
+	dget(dentry);
+	while (!IS_ROOT(dentry)) {
+		struct dentry *parent = dget_parent(dentry);
+
+		if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
+			dput(parent);
+			break;
+		}
+
+		dput(dentry);
+		dentry = parent;
+	}
+	return dentry;
+}
+
+/*
+ * Make sure target_dir is fully connected to the dentry tree.
+ *
+ * It may already be, as the flag isn't always updated when connection happens.
+ */
+static int
+reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
+{
+	int noprogress = 0;
+	int err = -ESTALE;
+
+	/*
+	 * It is possible that a confused file system might not let us complete
+	 * the path to the root.  For example, if get_parent returns a directory
+	 * in which we cannot find a name for the child.  While this implies a
+	 * very sick filesystem we don't want it to cause knfsd to spin.  Hence
+	 * the noprogress counter.  If we go through the loop 10 times (2 is
+	 * probably enough) without getting anywhere, we just give up
+	 */
+	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
+		struct dentry *pd = find_disconnected_root(target_dir);
+
+		if (!IS_ROOT(pd)) {
+			/* must have found a connected parent - great */
+			spin_lock(&pd->d_lock);
+			pd->d_flags &= ~DCACHE_DISCONNECTED;
+			spin_unlock(&pd->d_lock);
+			noprogress = 0;
+		} else if (pd == mnt->mnt_sb->s_root) {
+			printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
+			spin_lock(&pd->d_lock);
+			pd->d_flags &= ~DCACHE_DISCONNECTED;
+			spin_unlock(&pd->d_lock);
+			noprogress = 0;
+		} else {
+			/*
+			 * We have hit the top of a disconnected path, try to
+			 * find parent and connect.
+			 *
+			 * Racing with some other process renaming a directory
+			 * isn't much of a problem here.  If someone renames
+			 * the directory, it will end up properly connected,
+			 * which is what we want
+			 *
+			 * Getting the parent can't be supported generically,
+			 * the locking is too icky.
+			 *
+			 * Instead we just return EACCES.  If server reboots
+			 * or inodes get flushed, you lose
+			 */
+			struct dentry *ppd = ERR_PTR(-EACCES);
+			struct dentry *npd;
+
+			mutex_lock(&pd->d_inode->i_mutex);
+			if (mnt->mnt_sb->s_export_op->get_parent)
+				ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
+			mutex_unlock(&pd->d_inode->i_mutex);
+
+			if (IS_ERR(ppd)) {
+				err = PTR_ERR(ppd);
+				dprintk("%s: get_parent of %ld failed, err %d\n",
+					__func__, pd->d_inode->i_ino, err);
+				dput(pd);
+				break;
+			}
+
+			dprintk("%s: find name of %lu in %lu\n", __func__,
+				pd->d_inode->i_ino, ppd->d_inode->i_ino);
+			err = exportfs_get_name(mnt, ppd, nbuf, pd);
+			if (err) {
+				dput(ppd);
+				dput(pd);
+				if (err == -ENOENT)
+					/* some race between get_parent and
+					 * get_name?  just try again
+					 */
+					continue;
+				break;
+			}
+			dprintk("%s: found name: %s\n", __func__, nbuf);
+			mutex_lock(&ppd->d_inode->i_mutex);
+			npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
+			mutex_unlock(&ppd->d_inode->i_mutex);
+			if (IS_ERR(npd)) {
+				err = PTR_ERR(npd);
+				dprintk("%s: lookup failed: %d\n",
+					__func__, err);
+				dput(ppd);
+				dput(pd);
+				break;
+			}
+			/* we didn't really want npd, we really wanted
+			 * a side-effect of the lookup.
+			 * hopefully, npd == pd, though it isn't really
+			 * a problem if it isn't
+			 */
+			if (npd == pd)
+				noprogress = 0;
+			else
+				printk("%s: npd != pd\n", __func__);
+			dput(npd);
+			dput(ppd);
+			if (IS_ROOT(pd)) {
+				/* something went wrong, we have to give up */
+				dput(pd);
+				break;
+			}
+		}
+		dput(pd);
+	}
+
+	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
+		/* something went wrong - oh-well */
+		if (!err)
+			err = -ESTALE;
+		return err;
+	}
+
+	return 0;
+}
+
+struct getdents_callback {
+	char *name;		/* name that was found. It already points to a
+				   buffer NAME_MAX+1 is size */
+	unsigned long ino;	/* the inum we are looking for */
+	int found;		/* inode matched? */
+	int sequence;		/* sequence counter */
+};
+
+/*
+ * A rather strange filldir function to capture
+ * the name matching the specified inode number.
+ */
+static int filldir_one(void * __buf, const char * name, int len,
+			loff_t pos, u64 ino, unsigned int d_type)
+{
+	struct getdents_callback *buf = __buf;
+	int result = 0;
+
+	buf->sequence++;
+	if (buf->ino == ino) {
+		memcpy(buf->name, name, len);
+		buf->name[len] = '\0';
+		buf->found = 1;
+		result = -1;
+	}
+	return result;
+}
+
+/**
+ * get_name - default export_operations->get_name function
+ * @dentry: the directory in which to find a name
+ * @name:   a pointer to a %NAME_MAX+1 char buffer to store the name
+ * @child:  the dentry for the child directory.
+ *
+ * calls readdir on the parent until it finds an entry with
+ * the same inode number as the child, and returns that.
+ */
+static int get_name(struct vfsmount *mnt, struct dentry *dentry,
+		char *name, struct dentry *child)
+{
+	const struct cred *cred = current_cred();
+	struct inode *dir = dentry->d_inode;
+	int error;
+	struct file *file;
+	struct getdents_callback buffer;
+
+	error = -ENOTDIR;
+	if (!dir || !S_ISDIR(dir->i_mode))
+		goto out;
+	error = -EINVAL;
+	if (!dir->i_fop)
+		goto out;
+	/*
+	 * Open the directory ...
+	 */
+	file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
+	error = PTR_ERR(file);
+	if (IS_ERR(file))
+		goto out;
+
+	error = -EINVAL;
+	if (!file->f_op->readdir)
+		goto out_close;
+
+	buffer.name = name;
+	buffer.ino = child->d_inode->i_ino;
+	buffer.found = 0;
+	buffer.sequence = 0;
+	while (1) {
+		int old_seq = buffer.sequence;
+
+		error = vfs_readdir(file, filldir_one, &buffer);
+		if (buffer.found) {
+			error = 0;
+			break;
+		}
+
+		if (error < 0)
+			break;
+
+		error = -ENOENT;
+		if (old_seq == buffer.sequence)
+			break;
+	}
+
+out_close:
+	fput(file);
+out:
+	return error;
+}
+
+/**
+ * export_encode_fh - default export_operations->encode_fh function
+ * @dentry:  the dentry to encode
+ * @fh:      where to store the file handle fragment
+ * @max_len: maximum length to store there
+ * @connectable: whether to store parent information
+ *
+ * This default encode_fh function assumes that the 32 inode number
+ * is suitable for locating an inode, and that the generation number
+ * can be used to check that it is still valid.  It places them in the
+ * filehandle fragment where export_decode_fh expects to find them.
+ */
+static int export_encode_fh(struct dentry *dentry, struct fid *fid,
+		int *max_len, int connectable)
+{
+	struct inode * inode = dentry->d_inode;
+	int len = *max_len;
+	int type = FILEID_INO32_GEN;
+
+	if (connectable && (len < 4)) {
+		*max_len = 4;
+		return 255;
+	} else if (len < 2) {
+		*max_len = 2;
+		return 255;
+	}
+
+	len = 2;
+	fid->i32.ino = inode->i_ino;
+	fid->i32.gen = inode->i_generation;
+	if (connectable && !S_ISDIR(inode->i_mode)) {
+		struct inode *parent;
+
+		spin_lock(&dentry->d_lock);
+		parent = dentry->d_parent->d_inode;
+		fid->i32.parent_ino = parent->i_ino;
+		fid->i32.parent_gen = parent->i_generation;
+		spin_unlock(&dentry->d_lock);
+		len = 4;
+		type = FILEID_INO32_GEN_PARENT;
+	}
+	*max_len = len;
+	return type;
+}
+
+int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
+		int connectable)
+{
+	const struct export_operations *nop = dentry->d_sb->s_export_op;
+	int error;
+
+	if (nop->encode_fh)
+		error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
+	else
+		error = export_encode_fh(dentry, fid, max_len, connectable);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(exportfs_encode_fh);
+
+struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+		int fh_len, int fileid_type,
+		int (*acceptable)(void *, struct dentry *), void *context)
+{
+	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
+	struct dentry *result, *alias;
+	char nbuf[NAME_MAX+1];
+	int err;
+
+	/*
+	 * Try to get any dentry for the given file handle from the filesystem.
+	 */
+	if (!nop || !nop->fh_to_dentry)
+		return ERR_PTR(-ESTALE);
+	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
+	if (!result)
+		result = ERR_PTR(-ESTALE);
+	if (IS_ERR(result))
+		return result;
+
+	if (S_ISDIR(result->d_inode->i_mode)) {
+		/*
+		 * This request is for a directory.
+		 *
+		 * On the positive side there is only one dentry for each
+		 * directory inode.  On the negative side this implies that we
+		 * to ensure our dentry is connected all the way up to the
+		 * filesystem root.
+		 */
+		if (result->d_flags & DCACHE_DISCONNECTED) {
+			err = reconnect_path(mnt, result, nbuf);
+			if (err)
+				goto err_result;
+		}
+
+		if (!acceptable(context, result)) {
+			err = -EACCES;
+			goto err_result;
+		}
+
+		return result;
+	} else {
+		/*
+		 * It's not a directory.  Life is a little more complicated.
+		 */
+		struct dentry *target_dir, *nresult;
+
+		/*
+		 * See if either the dentry we just got from the filesystem
+		 * or any alias for it is acceptable.  This is always true
+		 * if this filesystem is exported without the subtreecheck
+		 * option.  If the filesystem is exported with the subtree
+		 * check option there's a fair chance we need to look at
+		 * the parent directory in the file handle and make sure
+		 * it's connected to the filesystem root.
+		 */
+		alias = find_acceptable_alias(result, acceptable, context);
+		if (alias)
+			return alias;
+
+		/*
+		 * Try to extract a dentry for the parent directory from the
+		 * file handle.  If this fails we'll have to give up.
+		 */
+		err = -ESTALE;
+		if (!nop->fh_to_parent)
+			goto err_result;
+
+		target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
+				fh_len, fileid_type);
+		if (!target_dir)
+			goto err_result;
+		err = PTR_ERR(target_dir);
+		if (IS_ERR(target_dir))
+			goto err_result;
+
+		/*
+		 * And as usual we need to make sure the parent directory is
+		 * connected to the filesystem root.  The VFS really doesn't
+		 * like disconnected directories..
+		 */
+		err = reconnect_path(mnt, target_dir, nbuf);
+		if (err) {
+			dput(target_dir);
+			goto err_result;
+		}
+
+		/*
+		 * Now that we've got both a well-connected parent and a
+		 * dentry for the inode we're after, make sure that our
+		 * inode is actually connected to the parent.
+		 */
+		err = exportfs_get_name(mnt, target_dir, nbuf, result);
+		if (!err) {
+			mutex_lock(&target_dir->d_inode->i_mutex);
+			nresult = lookup_one_len(nbuf, target_dir,
+						 strlen(nbuf));
+			mutex_unlock(&target_dir->d_inode->i_mutex);
+			if (!IS_ERR(nresult)) {
+				if (nresult->d_inode) {
+					dput(result);
+					result = nresult;
+				} else
+					dput(nresult);
+			}
+		}
+
+		/*
+		 * At this point we are done with the parent, but it's pinned
+		 * by the child dentry anyway.
+		 */
+		dput(target_dir);
+
+		/*
+		 * And finally make sure the dentry is actually acceptable
+		 * to NFSD.
+		 */
+		alias = find_acceptable_alias(result, acceptable, context);
+		if (!alias) {
+			err = -EACCES;
+			goto err_result;
+		}
+
+		return alias;
+	}
+
+ err_result:
+	dput(result);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(exportfs_decode_fh);
+
+MODULE_LICENSE("GPL");