initial_commit

1 files changed, 1692 insertions, 0 deletions

diff --git a/fs/bio.c b/fs/bio.c
new file mode 100644
index 00000000..9bfade8a
--- /dev/null
+++ b/fs/bio.c
@@ -0,0 +1,1692 @@
+/*
+ * Copyright (C) 2001 Jens Axboe <axboe@kernel.dk>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public Licens
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
+ *
+ */
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mempool.h>
+#include <linux/workqueue.h>
+#include <scsi/sg.h>		/* for struct sg_iovec */
+
+#include <trace/events/block.h>
+
+/*
+ * Test patch to inline a certain number of bi_io_vec's inside the bio
+ * itself, to shrink a bio data allocation from two mempool calls to one
+ */
+#define BIO_INLINE_VECS		4
+
+static mempool_t *bio_split_pool __read_mostly;
+
+/*
+ * if you change this list, also change bvec_alloc or things will
+ * break badly! cannot be bigger than what you can fit into an
+ * unsigned short
+ */
+#define BV(x) { .nr_vecs = x, .name = "biovec-"__stringify(x) }
+static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = {
+	BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
+};
+#undef BV
+
+/*
+ * fs_bio_set is the bio_set containing bio and iovec memory pools used by
+ * IO code that does not need private memory pools.
+ */
+struct bio_set *fs_bio_set;
+
+/*
+ * Our slab pool management
+ */
+struct bio_slab {
+	struct kmem_cache *slab;
+	unsigned int slab_ref;
+	unsigned int slab_size;
+	char name[8];
+};
+static DEFINE_MUTEX(bio_slab_lock);
+static struct bio_slab *bio_slabs;
+static unsigned int bio_slab_nr, bio_slab_max;
+
+static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
+{
+	unsigned int sz = sizeof(struct bio) + extra_size;
+	struct kmem_cache *slab = NULL;
+	struct bio_slab *bslab;
+	unsigned int i, entry = -1;
+
+	mutex_lock(&bio_slab_lock);
+
+	i = 0;
+	while (i < bio_slab_nr) {
+		bslab = &bio_slabs[i];
+
+		if (!bslab->slab && entry == -1)
+			entry = i;
+		else if (bslab->slab_size == sz) {
+			slab = bslab->slab;
+			bslab->slab_ref++;
+			break;
+		}
+		i++;
+	}
+
+	if (slab)
+		goto out_unlock;
+
+	if (bio_slab_nr == bio_slab_max && entry == -1) {
+		bio_slab_max <<= 1;
+		bio_slabs = krealloc(bio_slabs,
+				     bio_slab_max * sizeof(struct bio_slab),
+				     GFP_KERNEL);
+		if (!bio_slabs)
+			goto out_unlock;
+	}
+	if (entry == -1)
+		entry = bio_slab_nr++;
+
+	bslab = &bio_slabs[entry];
+
+	snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
+	slab = kmem_cache_create(bslab->name, sz, 0, SLAB_HWCACHE_ALIGN, NULL);
+	if (!slab)
+		goto out_unlock;
+
+	printk(KERN_INFO "bio: create slab <%s> at %d\n", bslab->name, entry);
+	bslab->slab = slab;
+	bslab->slab_ref = 1;
+	bslab->slab_size = sz;
+out_unlock:
+	mutex_unlock(&bio_slab_lock);
+	return slab;
+}
+
+static void bio_put_slab(struct bio_set *bs)
+{
+	struct bio_slab *bslab = NULL;
+	unsigned int i;
+
+	mutex_lock(&bio_slab_lock);
+
+	for (i = 0; i < bio_slab_nr; i++) {
+		if (bs->bio_slab == bio_slabs[i].slab) {
+			bslab = &bio_slabs[i];
+			break;
+		}
+	}
+
+	if (WARN(!bslab, KERN_ERR "bio: unable to find slab!\n"))
+		goto out;
+
+	WARN_ON(!bslab->slab_ref);
+
+	if (--bslab->slab_ref)
+		goto out;
+
+	kmem_cache_destroy(bslab->slab);
+	bslab->slab = NULL;
+
+out:
+	mutex_unlock(&bio_slab_lock);
+}
+
+unsigned int bvec_nr_vecs(unsigned short idx)
+{
+	return bvec_slabs[idx].nr_vecs;
+}
+
+void bvec_free_bs(struct bio_set *bs, struct bio_vec *bv, unsigned int idx)
+{
+	BIO_BUG_ON(idx >= BIOVEC_NR_POOLS);
+
+	if (idx == BIOVEC_MAX_IDX)
+		mempool_free(bv, bs->bvec_pool);
+	else {
+		struct biovec_slab *bvs = bvec_slabs + idx;
+
+		kmem_cache_free(bvs->slab, bv);
+	}
+}
+
+struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx,
+			      struct bio_set *bs)
+{
+	struct bio_vec *bvl;
+
+	/*
+	 * see comment near bvec_array define!
+	 */
+	switch (nr) {
+	case 1:
+		*idx = 0;
+		break;
+	case 2 ... 4:
+		*idx = 1;
+		break;
+	case 5 ... 16:
+		*idx = 2;
+		break;
+	case 17 ... 64:
+		*idx = 3;
+		break;
+	case 65 ... 128:
+		*idx = 4;
+		break;
+	case 129 ... BIO_MAX_PAGES:
+		*idx = 5;
+		break;
+	default:
+		return NULL;
+	}
+
+	/*
+	 * idx now points to the pool we want to allocate from. only the
+	 * 1-vec entry pool is mempool backed.
+	 */
+	if (*idx == BIOVEC_MAX_IDX) {
+fallback:
+		bvl = mempool_alloc(bs->bvec_pool, gfp_mask);
+	} else {
+		struct biovec_slab *bvs = bvec_slabs + *idx;
+		gfp_t __gfp_mask = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
+
+		/*
+		 * Make this allocation restricted and don't dump info on
+		 * allocation failures, since we'll fallback to the mempool
+		 * in case of failure.
+		 */
+		__gfp_mask |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
+
+		/*
+		 * Try a slab allocation. If this fails and __GFP_WAIT
+		 * is set, retry with the 1-entry mempool
+		 */
+		bvl = kmem_cache_alloc(bvs->slab, __gfp_mask);
+		if (unlikely(!bvl && (gfp_mask & __GFP_WAIT))) {
+			*idx = BIOVEC_MAX_IDX;
+			goto fallback;
+		}
+	}
+
+	return bvl;
+}
+
+void bio_free(struct bio *bio, struct bio_set *bs)
+{
+	void *p;
+
+	if (bio_has_allocated_vec(bio))
+		bvec_free_bs(bs, bio->bi_io_vec, BIO_POOL_IDX(bio));
+
+	if (bio_integrity(bio))
+		bio_integrity_free(bio, bs);
+
+	/*
+	 * If we have front padding, adjust the bio pointer before freeing
+	 */
+	p = bio;
+	if (bs->front_pad)
+		p -= bs->front_pad;
+
+	mempool_free(p, bs->bio_pool);
+}
+EXPORT_SYMBOL(bio_free);
+
+void bio_init(struct bio *bio)
+{
+	memset(bio, 0, sizeof(*bio));
+	bio->bi_flags = 1 << BIO_UPTODATE;
+	bio->bi_comp_cpu = -1;
+	atomic_set(&bio->bi_cnt, 1);
+}
+EXPORT_SYMBOL(bio_init);
+
+/**
+ * bio_alloc_bioset - allocate a bio for I/O
+ * @gfp_mask:   the GFP_ mask given to the slab allocator
+ * @nr_iovecs:	number of iovecs to pre-allocate
+ * @bs:		the bio_set to allocate from.
+ *
+ * Description:
+ *   bio_alloc_bioset will try its own mempool to satisfy the allocation.
+ *   If %__GFP_WAIT is set then we will block on the internal pool waiting
+ *   for a &struct bio to become free.
+ *
+ *   Note that the caller must set ->bi_destructor on successful return
+ *   of a bio, to do the appropriate freeing of the bio once the reference
+ *   count drops to zero.
+ **/
+struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
+{
+	unsigned long idx = BIO_POOL_NONE;
+	struct bio_vec *bvl = NULL;
+	struct bio *bio;
+	void *p;
+
+	p = mempool_alloc(bs->bio_pool, gfp_mask);
+	if (unlikely(!p))
+		return NULL;
+	bio = p + bs->front_pad;
+
+	bio_init(bio);
+
+	if (unlikely(!nr_iovecs))
+		goto out_set;
+
+	if (nr_iovecs <= BIO_INLINE_VECS) {
+		bvl = bio->bi_inline_vecs;
+		nr_iovecs = BIO_INLINE_VECS;
+	} else {
+		bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
+		if (unlikely(!bvl))
+			goto err_free;
+
+		nr_iovecs = bvec_nr_vecs(idx);
+	}
+out_set:
+	bio->bi_flags |= idx << BIO_POOL_OFFSET;
+	bio->bi_max_vecs = nr_iovecs;
+	bio->bi_io_vec = bvl;
+	return bio;
+
+err_free:
+	mempool_free(p, bs->bio_pool);
+	return NULL;
+}
+EXPORT_SYMBOL(bio_alloc_bioset);
+
+static void bio_fs_destructor(struct bio *bio)
+{
+	bio_free(bio, fs_bio_set);
+}
+
+/**
+ *	bio_alloc - allocate a new bio, memory pool backed
+ *	@gfp_mask: allocation mask to use
+ *	@nr_iovecs: number of iovecs
+ *
+ *	bio_alloc will allocate a bio and associated bio_vec array that can hold
+ *	at least @nr_iovecs entries. Allocations will be done from the
+ *	fs_bio_set. Also see @bio_alloc_bioset and @bio_kmalloc.
+ *
+ *	If %__GFP_WAIT is set, then bio_alloc will always be able to allocate
+ *	a bio. This is due to the mempool guarantees. To make this work, callers
+ *	must never allocate more than 1 bio at a time from this pool. Callers
+ *	that need to allocate more than 1 bio must always submit the previously
+ *	allocated bio for IO before attempting to allocate a new one. Failure to
+ *	do so can cause livelocks under memory pressure.
+ *
+ *	RETURNS:
+ *	Pointer to new bio on success, NULL on failure.
+ */
+struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)
+{
+	struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
+
+	if (bio)
+		bio->bi_destructor = bio_fs_destructor;
+
+	return bio;
+}
+EXPORT_SYMBOL(bio_alloc);
+
+static void bio_kmalloc_destructor(struct bio *bio)
+{
+	if (bio_integrity(bio))
+		bio_integrity_free(bio, fs_bio_set);
+	kfree(bio);
+}
+
+/**
+ * bio_kmalloc - allocate a bio for I/O using kmalloc()
+ * @gfp_mask:   the GFP_ mask given to the slab allocator
+ * @nr_iovecs:	number of iovecs to pre-allocate
+ *
+ * Description:
+ *   Allocate a new bio with @nr_iovecs bvecs.  If @gfp_mask contains
+ *   %__GFP_WAIT, the allocation is guaranteed to succeed.
+ *
+ **/
+struct bio *bio_kmalloc(gfp_t gfp_mask, int nr_iovecs)
+{
+	struct bio *bio;
+
+	if (nr_iovecs > UIO_MAXIOV)
+		return NULL;
+
+	bio = kmalloc(sizeof(struct bio) + nr_iovecs * sizeof(struct bio_vec),
+		      gfp_mask);
+	if (unlikely(!bio))
+		return NULL;
+
+	bio_init(bio);
+	bio->bi_flags |= BIO_POOL_NONE << BIO_POOL_OFFSET;
+	bio->bi_max_vecs = nr_iovecs;
+	bio->bi_io_vec = bio->bi_inline_vecs;
+	bio->bi_destructor = bio_kmalloc_destructor;
+
+	return bio;
+}
+EXPORT_SYMBOL(bio_kmalloc);
+
+void zero_fill_bio(struct bio *bio)
+{
+	unsigned long flags;
+	struct bio_vec *bv;
+	int i;
+
+	bio_for_each_segment(bv, bio, i) {
+		char *data = bvec_kmap_irq(bv, &flags);
+		memset(data, 0, bv->bv_len);
+		flush_dcache_page(bv->bv_page);
+		bvec_kunmap_irq(data, &flags);
+	}
+}
+EXPORT_SYMBOL(zero_fill_bio);
+
+/**
+ * bio_put - release a reference to a bio
+ * @bio:   bio to release reference to
+ *
+ * Description:
+ *   Put a reference to a &struct bio, either one you have gotten with
+ *   bio_alloc, bio_get or bio_clone. The last put of a bio will free it.
+ **/
+void bio_put(struct bio *bio)
+{
+	BIO_BUG_ON(!atomic_read(&bio->bi_cnt));
+
+	/*
+	 * last put frees it
+	 */
+	if (atomic_dec_and_test(&bio->bi_cnt)) {
+		bio->bi_next = NULL;
+		bio->bi_destructor(bio);
+	}
+}
+EXPORT_SYMBOL(bio_put);
+
+inline int bio_phys_segments(struct request_queue *q, struct bio *bio)
+{
+	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, bio);
+
+	return bio->bi_phys_segments;
+}
+EXPORT_SYMBOL(bio_phys_segments);
+
+/**
+ * 	__bio_clone	-	clone a bio
+ * 	@bio: destination bio
+ * 	@bio_src: bio to clone
+ *
+ *	Clone a &bio. Caller will own the returned bio, but not
+ *	the actual data it points to. Reference count of returned
+ * 	bio will be one.
+ */
+void __bio_clone(struct bio *bio, struct bio *bio_src)
+{
+	memcpy(bio->bi_io_vec, bio_src->bi_io_vec,
+		bio_src->bi_max_vecs * sizeof(struct bio_vec));
+
+	/*
+	 * most users will be overriding ->bi_bdev with a new target,
+	 * so we don't set nor calculate new physical/hw segment counts here
+	 */
+	bio->bi_sector = bio_src->bi_sector;
+	bio->bi_bdev = bio_src->bi_bdev;
+	bio->bi_flags |= 1 << BIO_CLONED;
+	bio->bi_rw = bio_src->bi_rw;
+	bio->bi_vcnt = bio_src->bi_vcnt;
+	bio->bi_size = bio_src->bi_size;
+	bio->bi_idx = bio_src->bi_idx;
+}
+EXPORT_SYMBOL(__bio_clone);
+
+/**
+ *	bio_clone	-	clone a bio
+ *	@bio: bio to clone
+ *	@gfp_mask: allocation priority
+ *
+ * 	Like __bio_clone, only also allocates the returned bio
+ */
+struct bio *bio_clone(struct bio *bio, gfp_t gfp_mask)
+{
+	struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, fs_bio_set);
+
+	if (!b)
+		return NULL;
+
+	b->bi_destructor = bio_fs_destructor;
+	__bio_clone(b, bio);
+
+	if (bio_integrity(bio)) {
+		int ret;
+
+		ret = bio_integrity_clone(b, bio, gfp_mask, fs_bio_set);
+
+		if (ret < 0) {
+			bio_put(b);
+			return NULL;
+		}
+	}
+
+	return b;
+}
+EXPORT_SYMBOL(bio_clone);
+
+/**
+ *	bio_get_nr_vecs		- return approx number of vecs
+ *	@bdev:  I/O target
+ *
+ *	Return the approximate number of pages we can send to this target.
+ *	There's no guarantee that you will be able to fit this number of pages
+ *	into a bio, it does not account for dynamic restrictions that vary
+ *	on offset.
+ */
+int bio_get_nr_vecs(struct block_device *bdev)
+{
+	struct request_queue *q = bdev_get_queue(bdev);
+	int nr_pages;
+
+	nr_pages = ((queue_max_sectors(q) << 9) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if (nr_pages > queue_max_segments(q))
+		nr_pages = queue_max_segments(q);
+
+	return nr_pages;
+}
+EXPORT_SYMBOL(bio_get_nr_vecs);
+
+static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
+			  *page, unsigned int len, unsigned int offset,
+			  unsigned short max_sectors)
+{
+	int retried_segments = 0;
+	struct bio_vec *bvec;
+
+	/*
+	 * cloned bio must not modify vec list
+	 */
+	if (unlikely(bio_flagged(bio, BIO_CLONED)))
+		return 0;
+
+	if (((bio->bi_size + len) >> 9) > max_sectors)
+		return 0;
+
+	/*
+	 * For filesystems with a blocksize smaller than the pagesize
+	 * we will often be called with the same page as last time and
+	 * a consecutive offset.  Optimize this special case.
+	 */
+	if (bio->bi_vcnt > 0) {
+		struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
+
+		if (page == prev->bv_page &&
+		    offset == prev->bv_offset + prev->bv_len) {
+			unsigned int prev_bv_len = prev->bv_len;
+			prev->bv_len += len;
+
+			if (q->merge_bvec_fn) {
+				struct bvec_merge_data bvm = {
+					/* prev_bvec is already charged in
+					   bi_size, discharge it in order to
+					   simulate merging updated prev_bvec
+					   as new bvec. */
+					.bi_bdev = bio->bi_bdev,
+					.bi_sector = bio->bi_sector,
+					.bi_size = bio->bi_size - prev_bv_len,
+					.bi_rw = bio->bi_rw,
+				};
+
+				if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len) {
+					prev->bv_len -= len;
+					return 0;
+				}
+			}
+
+			goto done;
+		}
+	}
+
+	if (bio->bi_vcnt >= bio->bi_max_vecs)
+		return 0;
+
+	/*
+	 * we might lose a segment or two here, but rather that than
+	 * make this too complex.
+	 */
+
+	while (bio->bi_phys_segments >= queue_max_segments(q)) {
+
+		if (retried_segments)
+			return 0;
+
+		retried_segments = 1;
+		blk_recount_segments(q, bio);
+	}
+
+	/*
+	 * setup the new entry, we might clear it again later if we
+	 * cannot add the page
+	 */
+	bvec = &bio->bi_io_vec[bio->bi_vcnt];
+	bvec->bv_page = page;
+	bvec->bv_len = len;
+	bvec->bv_offset = offset;
+
+	/*
+	 * if queue has other restrictions (eg varying max sector size
+	 * depending on offset), it can specify a merge_bvec_fn in the
+	 * queue to get further control
+	 */
+	if (q->merge_bvec_fn) {
+		struct bvec_merge_data bvm = {
+			.bi_bdev = bio->bi_bdev,
+			.bi_sector = bio->bi_sector,
+			.bi_size = bio->bi_size,
+			.bi_rw = bio->bi_rw,
+		};
+
+		/*
+		 * merge_bvec_fn() returns number of bytes it can accept
+		 * at this offset
+		 */
+		if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len) {
+			bvec->bv_page = NULL;
+			bvec->bv_len = 0;
+			bvec->bv_offset = 0;
+			return 0;
+		}
+	}
+
+	/* If we may be able to merge these biovecs, force a recount */
+	if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
+		bio->bi_flags &= ~(1 << BIO_SEG_VALID);
+
+	bio->bi_vcnt++;
+	bio->bi_phys_segments++;
+ done:
+	bio->bi_size += len;
+	return len;
+}
+
+/**
+ *	bio_add_pc_page	-	attempt to add page to bio
+ *	@q: the target queue
+ *	@bio: destination bio
+ *	@page: page to add
+ *	@len: vec entry length
+ *	@offset: vec entry offset
+ *
+ *	Attempt to add a page to the bio_vec maplist. This can fail for a
+ *	number of reasons, such as the bio being full or target block device
+ *	limitations. The target block device must allow bio's up to PAGE_SIZE,
+ *	so it is always possible to add a single page to an empty bio.
+ *
+ *	This should only be used by REQ_PC bios.
+ */
+int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page *page,
+		    unsigned int len, unsigned int offset)
+{
+	return __bio_add_page(q, bio, page, len, offset,
+			      queue_max_hw_sectors(q));
+}
+EXPORT_SYMBOL(bio_add_pc_page);
+
+/**
+ *	bio_add_page	-	attempt to add page to bio
+ *	@bio: destination bio
+ *	@page: page to add
+ *	@len: vec entry length
+ *	@offset: vec entry offset
+ *
+ *	Attempt to add a page to the bio_vec maplist. This can fail for a
+ *	number of reasons, such as the bio being full or target block device
+ *	limitations. The target block device must allow bio's up to PAGE_SIZE,
+ *	so it is always possible to add a single page to an empty bio.
+ */
+int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
+		 unsigned int offset)
+{
+	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+	return __bio_add_page(q, bio, page, len, offset, queue_max_sectors(q));
+}
+EXPORT_SYMBOL(bio_add_page);
+
+struct bio_map_data {
+	struct bio_vec *iovecs;
+	struct sg_iovec *sgvecs;
+	int nr_sgvecs;
+	int is_our_pages;
+};
+
+static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
+			     struct sg_iovec *iov, int iov_count,
+			     int is_our_pages)
+{
+	memcpy(bmd->iovecs, bio->bi_io_vec, sizeof(struct bio_vec) * bio->bi_vcnt);
+	memcpy(bmd->sgvecs, iov, sizeof(struct sg_iovec) * iov_count);
+	bmd->nr_sgvecs = iov_count;
+	bmd->is_our_pages = is_our_pages;
+	bio->bi_private = bmd;
+}
+
+static void bio_free_map_data(struct bio_map_data *bmd)
+{
+	kfree(bmd->iovecs);
+	kfree(bmd->sgvecs);
+	kfree(bmd);
+}
+
+static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count,
+					       gfp_t gfp_mask)
+{
+	struct bio_map_data *bmd;
+
+	if (iov_count > UIO_MAXIOV)
+		return NULL;
+
+	bmd = kmalloc(sizeof(*bmd), gfp_mask);
+	if (!bmd)
+		return NULL;
+
+	bmd->iovecs = kmalloc(sizeof(struct bio_vec) * nr_segs, gfp_mask);
+	if (!bmd->iovecs) {
+		kfree(bmd);
+		return NULL;
+	}
+
+	bmd->sgvecs = kmalloc(sizeof(struct sg_iovec) * iov_count, gfp_mask);
+	if (bmd->sgvecs)
+		return bmd;
+
+	kfree(bmd->iovecs);
+	kfree(bmd);
+	return NULL;
+}
+
+static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
+			  struct sg_iovec *iov, int iov_count,
+			  int to_user, int from_user, int do_free_page)
+{
+	int ret = 0, i;
+	struct bio_vec *bvec;
+	int iov_idx = 0;
+	unsigned int iov_off = 0;
+
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		char *bv_addr = page_address(bvec->bv_page);
+		unsigned int bv_len = iovecs[i].bv_len;
+
+		while (bv_len && iov_idx < iov_count) {
+			unsigned int bytes;
+			char __user *iov_addr;
+
+			bytes = min_t(unsigned int,
+				      iov[iov_idx].iov_len - iov_off, bv_len);
+			iov_addr = iov[iov_idx].iov_base + iov_off;
+
+			if (!ret) {
+				if (to_user)
+					ret = copy_to_user(iov_addr, bv_addr,
+							   bytes);
+
+				if (from_user)
+					ret = copy_from_user(bv_addr, iov_addr,
+							     bytes);
+
+				if (ret)
+					ret = -EFAULT;
+			}
+
+			bv_len -= bytes;
+			bv_addr += bytes;
+			iov_addr += bytes;
+			iov_off += bytes;
+
+			if (iov[iov_idx].iov_len == iov_off) {
+				iov_idx++;
+				iov_off = 0;
+			}
+		}
+
+		if (do_free_page)
+			__free_page(bvec->bv_page);
+	}
+
+	return ret;
+}
+
+/**
+ *	bio_uncopy_user	-	finish previously mapped bio
+ *	@bio: bio being terminated
+ *
+ *	Free pages allocated from bio_copy_user() and write back data
+ *	to user space in case of a read.
+ */
+int bio_uncopy_user(struct bio *bio)
+{
+	struct bio_map_data *bmd = bio->bi_private;
+	int ret = 0;
+
+	if (!bio_flagged(bio, BIO_NULL_MAPPED))
+		ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
+				     bmd->nr_sgvecs, bio_data_dir(bio) == READ,
+				     0, bmd->is_our_pages);
+	bio_free_map_data(bmd);
+	bio_put(bio);
+	return ret;
+}
+EXPORT_SYMBOL(bio_uncopy_user);
+
+/**
+ *	bio_copy_user_iov	-	copy user data to bio
+ *	@q: destination block queue
+ *	@map_data: pointer to the rq_map_data holding pages (if necessary)
+ *	@iov:	the iovec.
+ *	@iov_count: number of elements in the iovec
+ *	@write_to_vm: bool indicating writing to pages or not
+ *	@gfp_mask: memory allocation flags
+ *
+ *	Prepares and returns a bio for indirect user io, bouncing data
+ *	to/from kernel pages as necessary. Must be paired with
+ *	call bio_uncopy_user() on io completion.
+ */
+struct bio *bio_copy_user_iov(struct request_queue *q,
+			      struct rq_map_data *map_data,
+			      struct sg_iovec *iov, int iov_count,
+			      int write_to_vm, gfp_t gfp_mask)
+{
+	struct bio_map_data *bmd;
+	struct bio_vec *bvec;
+	struct page *page;
+	struct bio *bio;
+	int i, ret;
+	int nr_pages = 0;
+	unsigned int len = 0;
+	unsigned int offset = map_data ? map_data->offset & ~PAGE_MASK : 0;
+
+	for (i = 0; i < iov_count; i++) {
+		unsigned long uaddr;
+		unsigned long end;
+		unsigned long start;
+
+		uaddr = (unsigned long)iov[i].iov_base;
+		end = (uaddr + iov[i].iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		start = uaddr >> PAGE_SHIFT;
+
+		/*
+		 * Overflow, abort
+		 */
+		if (end < start)
+			return ERR_PTR(-EINVAL);
+
+		nr_pages += end - start;
+		len += iov[i].iov_len;
+	}
+
+	if (offset)
+		nr_pages++;
+
+	bmd = bio_alloc_map_data(nr_pages, iov_count, gfp_mask);
+	if (!bmd)
+		return ERR_PTR(-ENOMEM);
+
+	ret = -ENOMEM;
+	bio = bio_kmalloc(gfp_mask, nr_pages);
+	if (!bio)
+		goto out_bmd;
+
+	if (!write_to_vm)
+		bio->bi_rw |= REQ_WRITE;
+
+	ret = 0;
+
+	if (map_data) {
+		nr_pages = 1 << map_data->page_order;
+		i = map_data->offset / PAGE_SIZE;
+	}
+	while (len) {
+		unsigned int bytes = PAGE_SIZE;
+
+		bytes -= offset;
+
+		if (bytes > len)
+			bytes = len;
+
+		if (map_data) {
+			if (i == map_data->nr_entries * nr_pages) {
+				ret = -ENOMEM;
+				break;
+			}
+
+			page = map_data->pages[i / nr_pages];
+			page += (i % nr_pages);
+
+			i++;
+		} else {
+			page = alloc_page(q->bounce_gfp | gfp_mask);
+			if (!page) {
+				ret = -ENOMEM;
+				break;
+			}
+		}
+
+		if (bio_add_pc_page(q, bio, page, bytes, offset) < bytes)
+			break;
+
+		len -= bytes;
+		offset = 0;
+	}
+
+	if (ret)
+		goto cleanup;
+
+	/*
+	 * success
+	 */
+	if ((!write_to_vm && (!map_data || !map_data->null_mapped)) ||
+	    (map_data && map_data->from_user)) {
+		ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 1, 0);
+		if (ret)
+			goto cleanup;
+	}
+
+	bio_set_map_data(bmd, bio, iov, iov_count, map_data ? 0 : 1);
+	return bio;
+cleanup:
+	if (!map_data)
+		bio_for_each_segment(bvec, bio, i)
+			__free_page(bvec->bv_page);
+
+	bio_put(bio);
+out_bmd:
+	bio_free_map_data(bmd);
+	return ERR_PTR(ret);
+}
+
+/**
+ *	bio_copy_user	-	copy user data to bio
+ *	@q: destination block queue
+ *	@map_data: pointer to the rq_map_data holding pages (if necessary)
+ *	@uaddr: start of user address
+ *	@len: length in bytes
+ *	@write_to_vm: bool indicating writing to pages or not
+ *	@gfp_mask: memory allocation flags
+ *
+ *	Prepares and returns a bio for indirect user io, bouncing data
+ *	to/from kernel pages as necessary. Must be paired with
+ *	call bio_uncopy_user() on io completion.
+ */
+struct bio *bio_copy_user(struct request_queue *q, struct rq_map_data *map_data,
+			  unsigned long uaddr, unsigned int len,
+			  int write_to_vm, gfp_t gfp_mask)
+{
+	struct sg_iovec iov;
+
+	iov.iov_base = (void __user *)uaddr;
+	iov.iov_len = len;
+
+	return bio_copy_user_iov(q, map_data, &iov, 1, write_to_vm, gfp_mask);
+}
+EXPORT_SYMBOL(bio_copy_user);
+
+static struct bio *__bio_map_user_iov(struct request_queue *q,
+				      struct block_device *bdev,
+				      struct sg_iovec *iov, int iov_count,
+				      int write_to_vm, gfp_t gfp_mask)
+{
+	int i, j;
+	int nr_pages = 0;
+	struct page **pages;
+	struct bio *bio;
+	int cur_page = 0;
+	int ret, offset;
+
+	for (i = 0; i < iov_count; i++) {
+		unsigned long uaddr = (unsigned long)iov[i].iov_base;
+		unsigned long len = iov[i].iov_len;
+		unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		unsigned long start = uaddr >> PAGE_SHIFT;
+
+		/*
+		 * Overflow, abort
+		 */
+		if (end < start)
+			return ERR_PTR(-EINVAL);
+
+		nr_pages += end - start;
+		/*
+		 * buffer must be aligned to at least hardsector size for now
+		 */
+		if (uaddr & queue_dma_alignment(q))
+			return ERR_PTR(-EINVAL);
+	}
+
+	if (!nr_pages)
+		return ERR_PTR(-EINVAL);
+
+	bio = bio_kmalloc(gfp_mask, nr_pages);
+	if (!bio)
+		return ERR_PTR(-ENOMEM);
+
+	ret = -ENOMEM;
+	pages = kcalloc(nr_pages, sizeof(struct page *), gfp_mask);
+	if (!pages)
+		goto out;
+
+	for (i = 0; i < iov_count; i++) {
+		unsigned long uaddr = (unsigned long)iov[i].iov_base;
+		unsigned long len = iov[i].iov_len;
+		unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		unsigned long start = uaddr >> PAGE_SHIFT;
+		const int local_nr_pages = end - start;
+		const int page_limit = cur_page + local_nr_pages;
+
+		ret = get_user_pages_fast(uaddr, local_nr_pages,
+				write_to_vm, &pages[cur_page]);
+		if (ret < local_nr_pages) {
+			ret = -EFAULT;
+			goto out_unmap;
+		}
+
+		offset = uaddr & ~PAGE_MASK;
+		for (j = cur_page; j < page_limit; j++) {
+			unsigned int bytes = PAGE_SIZE - offset;
+
+			if (len <= 0)
+				break;
+			
+			if (bytes > len)
+				bytes = len;
+
+			/*
+			 * sorry...
+			 */
+			if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
+					    bytes)
+				break;
+
+			len -= bytes;
+			offset = 0;
+		}
+
+		cur_page = j;
+		/*
+		 * release the pages we didn't map into the bio, if any
+		 */
+		while (j < page_limit)
+			page_cache_release(pages[j++]);
+	}
+
+	kfree(pages);
+
+	/*
+	 * set data direction, and check if mapped pages need bouncing
+	 */
+	if (!write_to_vm)
+		bio->bi_rw |= REQ_WRITE;
+
+	bio->bi_bdev = bdev;
+	bio->bi_flags |= (1 << BIO_USER_MAPPED);
+	return bio;
+
+ out_unmap:
+	for (i = 0; i < nr_pages; i++) {
+		if(!pages[i])
+			break;
+		page_cache_release(pages[i]);
+	}
+ out:
+	kfree(pages);
+	bio_put(bio);
+	return ERR_PTR(ret);
+}
+
+/**
+ *	bio_map_user	-	map user address into bio
+ *	@q: the struct request_queue for the bio
+ *	@bdev: destination block device
+ *	@uaddr: start of user address
+ *	@len: length in bytes
+ *	@write_to_vm: bool indicating writing to pages or not
+ *	@gfp_mask: memory allocation flags
+ *
+ *	Map the user space address into a bio suitable for io to a block
+ *	device. Returns an error pointer in case of error.
+ */
+struct bio *bio_map_user(struct request_queue *q, struct block_device *bdev,
+			 unsigned long uaddr, unsigned int len, int write_to_vm,
+			 gfp_t gfp_mask)
+{
+	struct sg_iovec iov;
+
+	iov.iov_base = (void __user *)uaddr;
+	iov.iov_len = len;
+
+	return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm, gfp_mask);
+}
+EXPORT_SYMBOL(bio_map_user);
+
+/**
+ *	bio_map_user_iov - map user sg_iovec table into bio
+ *	@q: the struct request_queue for the bio
+ *	@bdev: destination block device
+ *	@iov:	the iovec.
+ *	@iov_count: number of elements in the iovec
+ *	@write_to_vm: bool indicating writing to pages or not
+ *	@gfp_mask: memory allocation flags
+ *
+ *	Map the user space address into a bio suitable for io to a block
+ *	device. Returns an error pointer in case of error.
+ */
+struct bio *bio_map_user_iov(struct request_queue *q, struct block_device *bdev,
+			     struct sg_iovec *iov, int iov_count,
+			     int write_to_vm, gfp_t gfp_mask)
+{
+	struct bio *bio;
+
+	bio = __bio_map_user_iov(q, bdev, iov, iov_count, write_to_vm,
+				 gfp_mask);
+	if (IS_ERR(bio))
+		return bio;
+
+	/*
+	 * subtle -- if __bio_map_user() ended up bouncing a bio,
+	 * it would normally disappear when its bi_end_io is run.
+	 * however, we need it for the unmap, so grab an extra
+	 * reference to it
+	 */
+	bio_get(bio);
+
+	return bio;
+}
+
+static void __bio_unmap_user(struct bio *bio)
+{
+	struct bio_vec *bvec;
+	int i;
+
+	/*
+	 * make sure we dirty pages we wrote to
+	 */
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		if (bio_data_dir(bio) == READ)
+			set_page_dirty_lock(bvec->bv_page);
+
+		page_cache_release(bvec->bv_page);
+	}
+
+	bio_put(bio);
+}
+
+/**
+ *	bio_unmap_user	-	unmap a bio
+ *	@bio:		the bio being unmapped
+ *
+ *	Unmap a bio previously mapped by bio_map_user(). Must be called with
+ *	a process context.
+ *
+ *	bio_unmap_user() may sleep.
+ */
+void bio_unmap_user(struct bio *bio)
+{
+	__bio_unmap_user(bio);
+	bio_put(bio);
+}
+EXPORT_SYMBOL(bio_unmap_user);
+
+static void bio_map_kern_endio(struct bio *bio, int err)
+{
+	bio_put(bio);
+}
+
+static struct bio *__bio_map_kern(struct request_queue *q, void *data,
+				  unsigned int len, gfp_t gfp_mask)
+{
+	unsigned long kaddr = (unsigned long)data;
+	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	unsigned long start = kaddr >> PAGE_SHIFT;
+	const int nr_pages = end - start;
+	int offset, i;
+	struct bio *bio;
+
+	bio = bio_kmalloc(gfp_mask, nr_pages);
+	if (!bio)
+		return ERR_PTR(-ENOMEM);
+
+	offset = offset_in_page(kaddr);
+	for (i = 0; i < nr_pages; i++) {
+		unsigned int bytes = PAGE_SIZE - offset;
+
+		if (len <= 0)
+			break;
+
+		if (bytes > len)
+			bytes = len;
+
+		if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
+				    offset) < bytes)
+			break;
+
+		data += bytes;
+		len -= bytes;
+		offset = 0;
+	}
+
+	bio->bi_end_io = bio_map_kern_endio;
+	return bio;
+}
+
+/**
+ *	bio_map_kern	-	map kernel address into bio
+ *	@q: the struct request_queue for the bio
+ *	@data: pointer to buffer to map
+ *	@len: length in bytes
+ *	@gfp_mask: allocation flags for bio allocation
+ *
+ *	Map the kernel address into a bio suitable for io to a block
+ *	device. Returns an error pointer in case of error.
+ */
+struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
+			 gfp_t gfp_mask)
+{
+	struct bio *bio;
+
+	bio = __bio_map_kern(q, data, len, gfp_mask);
+	if (IS_ERR(bio))
+		return bio;
+
+	if (bio->bi_size == len)
+		return bio;
+
+	/*
+	 * Don't support partial mappings.
+	 */
+	bio_put(bio);
+	return ERR_PTR(-EINVAL);
+}
+EXPORT_SYMBOL(bio_map_kern);
+
+static void bio_copy_kern_endio(struct bio *bio, int err)
+{
+	struct bio_vec *bvec;
+	const int read = bio_data_dir(bio) == READ;
+	struct bio_map_data *bmd = bio->bi_private;
+	int i;
+	char *p = bmd->sgvecs[0].iov_base;
+
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		char *addr = page_address(bvec->bv_page);
+		int len = bmd->iovecs[i].bv_len;
+
+		if (read)
+			memcpy(p, addr, len);
+
+		__free_page(bvec->bv_page);
+		p += len;
+	}
+
+	bio_free_map_data(bmd);
+	bio_put(bio);
+}
+
+/**
+ *	bio_copy_kern	-	copy kernel address into bio
+ *	@q: the struct request_queue for the bio
+ *	@data: pointer to buffer to copy
+ *	@len: length in bytes
+ *	@gfp_mask: allocation flags for bio and page allocation
+ *	@reading: data direction is READ
+ *
+ *	copy the kernel address into a bio suitable for io to a block
+ *	device. Returns an error pointer in case of error.
+ */
+struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
+			  gfp_t gfp_mask, int reading)
+{
+	struct bio *bio;
+	struct bio_vec *bvec;
+	int i;
+
+	bio = bio_copy_user(q, NULL, (unsigned long)data, len, 1, gfp_mask);
+	if (IS_ERR(bio))
+		return bio;
+
+	if (!reading) {
+		void *p = data;
+
+		bio_for_each_segment(bvec, bio, i) {
+			char *addr = page_address(bvec->bv_page);
+
+			memcpy(addr, p, bvec->bv_len);
+			p += bvec->bv_len;
+		}
+	}
+
+	bio->bi_end_io = bio_copy_kern_endio;
+
+	return bio;
+}
+EXPORT_SYMBOL(bio_copy_kern);
+
+/*
+ * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
+ * for performing direct-IO in BIOs.
+ *
+ * The problem is that we cannot run set_page_dirty() from interrupt context
+ * because the required locks are not interrupt-safe.  So what we can do is to
+ * mark the pages dirty _before_ performing IO.  And in interrupt context,
+ * check that the pages are still dirty.   If so, fine.  If not, redirty them
+ * in process context.
+ *
+ * We special-case compound pages here: normally this means reads into hugetlb
+ * pages.  The logic in here doesn't really work right for compound pages
+ * because the VM does not uniformly chase down the head page in all cases.
+ * But dirtiness of compound pages is pretty meaningless anyway: the VM doesn't
+ * handle them at all.  So we skip compound pages here at an early stage.
+ *
+ * Note that this code is very hard to test under normal circumstances because
+ * direct-io pins the pages with get_user_pages().  This makes
+ * is_page_cache_freeable return false, and the VM will not clean the pages.
+ * But other code (eg, pdflush) could clean the pages if they are mapped
+ * pagecache.
+ *
+ * Simply disabling the call to bio_set_pages_dirty() is a good way to test the
+ * deferred bio dirtying paths.
+ */
+
+/*
+ * bio_set_pages_dirty() will mark all the bio's pages as dirty.
+ */
+void bio_set_pages_dirty(struct bio *bio)
+{
+	struct bio_vec *bvec = bio->bi_io_vec;
+	int i;
+
+	for (i = 0; i < bio->bi_vcnt; i++) {
+		struct page *page = bvec[i].bv_page;
+
+		if (page && !PageCompound(page))
+			set_page_dirty_lock(page);
+	}
+}
+
+static void bio_release_pages(struct bio *bio)
+{
+	struct bio_vec *bvec = bio->bi_io_vec;
+	int i;
+
+	for (i = 0; i < bio->bi_vcnt; i++) {
+		struct page *page = bvec[i].bv_page;
+
+		if (page)
+			put_page(page);
+	}
+}
+
+/*
+ * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
+ * If they are, then fine.  If, however, some pages are clean then they must
+ * have been written out during the direct-IO read.  So we take another ref on
+ * the BIO and the offending pages and re-dirty the pages in process context.
+ *
+ * It is expected that bio_check_pages_dirty() will wholly own the BIO from
+ * here on.  It will run one page_cache_release() against each page and will
+ * run one bio_put() against the BIO.
+ */
+
+static void bio_dirty_fn(struct work_struct *work);
+
+static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
+static DEFINE_SPINLOCK(bio_dirty_lock);
+static struct bio *bio_dirty_list;
+
+/*
+ * This runs in process context
+ */
+static void bio_dirty_fn(struct work_struct *work)
+{
+	unsigned long flags;
+	struct bio *bio;
+
+	spin_lock_irqsave(&bio_dirty_lock, flags);
+	bio = bio_dirty_list;
+	bio_dirty_list = NULL;
+	spin_unlock_irqrestore(&bio_dirty_lock, flags);
+
+	while (bio) {
+		struct bio *next = bio->bi_private;
+
+		bio_set_pages_dirty(bio);
+		bio_release_pages(bio);
+		bio_put(bio);
+		bio = next;
+	}
+}
+
+void bio_check_pages_dirty(struct bio *bio)
+{
+	struct bio_vec *bvec = bio->bi_io_vec;
+	int nr_clean_pages = 0;
+	int i;
+
+	for (i = 0; i < bio->bi_vcnt; i++) {
+		struct page *page = bvec[i].bv_page;
+
+		if (PageDirty(page) || PageCompound(page)) {
+			page_cache_release(page);
+			bvec[i].bv_page = NULL;
+		} else {
+			nr_clean_pages++;
+		}
+	}
+
+	if (nr_clean_pages) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&bio_dirty_lock, flags);
+		bio->bi_private = bio_dirty_list;
+		bio_dirty_list = bio;
+		spin_unlock_irqrestore(&bio_dirty_lock, flags);
+		schedule_work(&bio_dirty_work);
+	} else {
+		bio_put(bio);
+	}
+}
+
+#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
+void bio_flush_dcache_pages(struct bio *bi)
+{
+	int i;
+	struct bio_vec *bvec;
+
+	bio_for_each_segment(bvec, bi, i)
+		flush_dcache_page(bvec->bv_page);
+}
+EXPORT_SYMBOL(bio_flush_dcache_pages);
+#endif
+
+/**
+ * bio_endio - end I/O on a bio
+ * @bio:	bio
+ * @error:	error, if any
+ *
+ * Description:
+ *   bio_endio() will end I/O on the whole bio. bio_endio() is the
+ *   preferred way to end I/O on a bio, it takes care of clearing
+ *   BIO_UPTODATE on error. @error is 0 on success, and and one of the
+ *   established -Exxxx (-EIO, for instance) error values in case
+ *   something went wrong. No one should call bi_end_io() directly on a
+ *   bio unless they own it and thus know that it has an end_io
+ *   function.
+ **/
+void bio_endio(struct bio *bio, int error)
+{
+	if (error)
+		clear_bit(BIO_UPTODATE, &bio->bi_flags);
+	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+		error = -EIO;
+
+	if (bio->bi_end_io)
+		bio->bi_end_io(bio, error);
+}
+EXPORT_SYMBOL(bio_endio);
+
+void bio_pair_release(struct bio_pair *bp)
+{
+	if (atomic_dec_and_test(&bp->cnt)) {
+		struct bio *master = bp->bio1.bi_private;
+
+		bio_endio(master, bp->error);
+		mempool_free(bp, bp->bio2.bi_private);
+	}
+}
+EXPORT_SYMBOL(bio_pair_release);
+
+static void bio_pair_end_1(struct bio *bi, int err)
+{
+	struct bio_pair *bp = container_of(bi, struct bio_pair, bio1);
+
+	if (err)
+		bp->error = err;
+
+	bio_pair_release(bp);
+}
+
+static void bio_pair_end_2(struct bio *bi, int err)
+{
+	struct bio_pair *bp = container_of(bi, struct bio_pair, bio2);
+
+	if (err)
+		bp->error = err;
+
+	bio_pair_release(bp);
+}
+
+/*
+ * split a bio - only worry about a bio with a single page in its iovec
+ */
+struct bio_pair *bio_split(struct bio *bi, int first_sectors)
+{
+	struct bio_pair *bp = mempool_alloc(bio_split_pool, GFP_NOIO);
+
+	if (!bp)
+		return bp;
+
+	trace_block_split(bdev_get_queue(bi->bi_bdev), bi,
+				bi->bi_sector + first_sectors);
+
+	BUG_ON(bi->bi_vcnt != 1);
+	BUG_ON(bi->bi_idx != 0);
+	atomic_set(&bp->cnt, 3);
+	bp->error = 0;
+	bp->bio1 = *bi;
+	bp->bio2 = *bi;
+	bp->bio2.bi_sector += first_sectors;
+	bp->bio2.bi_size -= first_sectors << 9;
+	bp->bio1.bi_size = first_sectors << 9;
+
+	bp->bv1 = bi->bi_io_vec[0];
+	bp->bv2 = bi->bi_io_vec[0];
+	bp->bv2.bv_offset += first_sectors << 9;
+	bp->bv2.bv_len -= first_sectors << 9;
+	bp->bv1.bv_len = first_sectors << 9;
+
+	bp->bio1.bi_io_vec = &bp->bv1;
+	bp->bio2.bi_io_vec = &bp->bv2;
+
+	bp->bio1.bi_max_vecs = 1;
+	bp->bio2.bi_max_vecs = 1;
+
+	bp->bio1.bi_end_io = bio_pair_end_1;
+	bp->bio2.bi_end_io = bio_pair_end_2;
+
+	bp->bio1.bi_private = bi;
+	bp->bio2.bi_private = bio_split_pool;
+
+	if (bio_integrity(bi))
+		bio_integrity_split(bi, bp, first_sectors);
+
+	return bp;
+}
+EXPORT_SYMBOL(bio_split);
+
+/**
+ *      bio_sector_offset - Find hardware sector offset in bio
+ *      @bio:           bio to inspect
+ *      @index:         bio_vec index
+ *      @offset:        offset in bv_page
+ *
+ *      Return the number of hardware sectors between beginning of bio
+ *      and an end point indicated by a bio_vec index and an offset
+ *      within that vector's page.
+ */
+sector_t bio_sector_offset(struct bio *bio, unsigned short index,
+			   unsigned int offset)
+{
+	unsigned int sector_sz;
+	struct bio_vec *bv;
+	sector_t sectors;
+	int i;
+
+	sector_sz = queue_logical_block_size(bio->bi_bdev->bd_disk->queue);
+	sectors = 0;
+
+	if (index >= bio->bi_idx)
+		index = bio->bi_vcnt - 1;
+
+	__bio_for_each_segment(bv, bio, i, 0) {
+		if (i == index) {
+			if (offset > bv->bv_offset)
+				sectors += (offset - bv->bv_offset) / sector_sz;
+			break;
+		}
+
+		sectors += bv->bv_len / sector_sz;
+	}
+
+	return sectors;
+}
+EXPORT_SYMBOL(bio_sector_offset);
+
+/*
+ * create memory pools for biovec's in a bio_set.
+ * use the global biovec slabs created for general use.
+ */
+static int biovec_create_pools(struct bio_set *bs, int pool_entries)
+{
+	struct biovec_slab *bp = bvec_slabs + BIOVEC_MAX_IDX;
+
+	bs->bvec_pool = mempool_create_slab_pool(pool_entries, bp->slab);
+	if (!bs->bvec_pool)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void biovec_free_pools(struct bio_set *bs)
+{
+	mempool_destroy(bs->bvec_pool);
+}
+
+void bioset_free(struct bio_set *bs)
+{
+	if (bs->bio_pool)
+		mempool_destroy(bs->bio_pool);
+
+	bioset_integrity_free(bs);
+	biovec_free_pools(bs);
+	bio_put_slab(bs);
+
+	kfree(bs);
+}
+EXPORT_SYMBOL(bioset_free);
+
+/**
+ * bioset_create  - Create a bio_set
+ * @pool_size:	Number of bio and bio_vecs to cache in the mempool
+ * @front_pad:	Number of bytes to allocate in front of the returned bio
+ *
+ * Description:
+ *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
+ *    to ask for a number of bytes to be allocated in front of the bio.
+ *    Front pad allocation is useful for embedding the bio inside
+ *    another structure, to avoid allocating extra data to go with the bio.
+ *    Note that the bio must be embedded at the END of that structure always,
+ *    or things will break badly.
+ */
+struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
+{
+	unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
+	struct bio_set *bs;
+
+	bs = kzalloc(sizeof(*bs), GFP_KERNEL);
+	if (!bs)
+		return NULL;
+
+	bs->front_pad = front_pad;
+
+	bs->bio_slab = bio_find_or_create_slab(front_pad + back_pad);
+	if (!bs->bio_slab) {
+		kfree(bs);
+		return NULL;
+	}
+
+	bs->bio_pool = mempool_create_slab_pool(pool_size, bs->bio_slab);
+	if (!bs->bio_pool)
+		goto bad;
+
+	if (!biovec_create_pools(bs, pool_size))
+		return bs;
+
+bad:
+	bioset_free(bs);
+	return NULL;
+}
+EXPORT_SYMBOL(bioset_create);
+
+static void __init biovec_init_slabs(void)
+{
+	int i;
+
+	for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+		int size;
+		struct biovec_slab *bvs = bvec_slabs + i;
+
+		if (bvs->nr_vecs <= BIO_INLINE_VECS) {
+			bvs->slab = NULL;
+			continue;
+		}
+
+		size = bvs->nr_vecs * sizeof(struct bio_vec);
+		bvs->slab = kmem_cache_create(bvs->name, size, 0,
+                                SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+	}
+}
+
+static int __init init_bio(void)
+{
+	bio_slab_max = 2;
+	bio_slab_nr = 0;
+	bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
+	if (!bio_slabs)
+		panic("bio: can't allocate bios\n");
+
+	bio_integrity_init();
+	biovec_init_slabs();
+
+	fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
+	if (!fs_bio_set)
+		panic("bio: can't allocate bios\n");
+
+	if (bioset_integrity_create(fs_bio_set, BIO_POOL_SIZE))
+		panic("bio: can't create integrity pool\n");
+
+	bio_split_pool = mempool_create_kmalloc_pool(BIO_SPLIT_ENTRIES,
+						     sizeof(struct bio_pair));
+	if (!bio_split_pool)
+		panic("bio: can't create split pool\n");
+
+	return 0;
+}
+subsys_initcall(init_bio);