diff --git a/fs/bio.c b/fs/bio.c
new file mode 100644
index 0000000..e5349e8
--- /dev/null
+++ b/fs/bio.c
@@ -0,0 +1,1096 @@
+/*
+ * Copyright (C) 2001 Jens Axboe <axboe@suse.de>
+ *
+ * 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>
+
+#define BIO_POOL_SIZE 256
+
+static kmem_cache_t *bio_slab;
+
+#define BIOVEC_NR_POOLS 6
+
+/*
+ * a small number of entries is fine, not going to be performance critical.
+ * basically we just need to survive
+ */
+#define BIO_SPLIT_ENTRIES 8	
+mempool_t *bio_split_pool;
+
+struct biovec_slab {
+	int nr_vecs;
+	char *name; 
+	kmem_cache_t *slab;
+};
+
+/*
+ * 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] = {
+	BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
+};
+#undef BV
+
+/*
+ * bio_set is used to allow other portions of the IO system to
+ * allocate their own private memory pools for bio and iovec structures.
+ * These memory pools in turn all allocate from the bio_slab
+ * and the bvec_slabs[].
+ */
+struct bio_set {
+	mempool_t *bio_pool;
+	mempool_t *bvec_pools[BIOVEC_NR_POOLS];
+};
+
+/*
+ * fs_bio_set is the bio_set containing bio and iovec memory pools used by
+ * IO code that does not need private memory pools.
+ */
+static struct bio_set *fs_bio_set;
+
+static inline struct bio_vec *bvec_alloc_bs(unsigned int __nocast gfp_mask, int nr, unsigned long *idx, struct bio_set *bs)
+{
+	struct bio_vec *bvl;
+	struct biovec_slab *bp;
+
+	/*
+	 * 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
+	 */
+
+	bp = bvec_slabs + *idx;
+	bvl = mempool_alloc(bs->bvec_pools[*idx], gfp_mask);
+	if (bvl)
+		memset(bvl, 0, bp->nr_vecs * sizeof(struct bio_vec));
+
+	return bvl;
+}
+
+/*
+ * default destructor for a bio allocated with bio_alloc_bioset()
+ */
+static void bio_destructor(struct bio *bio)
+{
+	const int pool_idx = BIO_POOL_IDX(bio);
+	struct bio_set *bs = bio->bi_set;
+
+	BIO_BUG_ON(pool_idx >= BIOVEC_NR_POOLS);
+
+	mempool_free(bio->bi_io_vec, bs->bvec_pools[pool_idx]);
+	mempool_free(bio, bs->bio_pool);
+}
+
+inline void bio_init(struct bio *bio)
+{
+	bio->bi_next = NULL;
+	bio->bi_flags = 1 << BIO_UPTODATE;
+	bio->bi_rw = 0;
+	bio->bi_vcnt = 0;
+	bio->bi_idx = 0;
+	bio->bi_phys_segments = 0;
+	bio->bi_hw_segments = 0;
+	bio->bi_hw_front_size = 0;
+	bio->bi_hw_back_size = 0;
+	bio->bi_size = 0;
+	bio->bi_max_vecs = 0;
+	bio->bi_end_io = NULL;
+	atomic_set(&bio->bi_cnt, 1);
+	bio->bi_private = NULL;
+}
+
+/**
+ * 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
+ *
+ * Description:
+ *   bio_alloc_bioset will first try it's on 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.
+ *
+ *   allocate bio and iovecs from the memory pools specified by the
+ *   bio_set structure.
+ **/
+struct bio *bio_alloc_bioset(unsigned int __nocast gfp_mask, int nr_iovecs, struct bio_set *bs)
+{
+	struct bio *bio = mempool_alloc(bs->bio_pool, gfp_mask);
+
+	if (likely(bio)) {
+		struct bio_vec *bvl = NULL;
+
+		bio_init(bio);
+		if (likely(nr_iovecs)) {
+			unsigned long idx;
+
+			bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
+			if (unlikely(!bvl)) {
+				mempool_free(bio, bs->bio_pool);
+				bio = NULL;
+				goto out;
+			}
+			bio->bi_flags |= idx << BIO_POOL_OFFSET;
+			bio->bi_max_vecs = bvec_slabs[idx].nr_vecs;
+		}
+		bio->bi_io_vec = bvl;
+		bio->bi_destructor = bio_destructor;
+		bio->bi_set = bs;
+	}
+out:
+	return bio;
+}
+
+struct bio *bio_alloc(unsigned int __nocast gfp_mask, int nr_iovecs)
+{
+	return bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
+}
+
+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 or bio_get. 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);
+	}
+}
+
+inline int bio_phys_segments(request_queue_t *q, struct bio *bio)
+{
+	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, bio);
+
+	return bio->bi_phys_segments;
+}
+
+inline int bio_hw_segments(request_queue_t *q, struct bio *bio)
+{
+	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, bio);
+
+	return bio->bi_hw_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.
+ */
+inline void __bio_clone(struct bio *bio, struct bio *bio_src)
+{
+	request_queue_t *q = bdev_get_queue(bio_src->bi_bdev);
+
+	memcpy(bio->bi_io_vec, bio_src->bi_io_vec, bio_src->bi_max_vecs * sizeof(struct bio_vec));
+
+	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;
+
+	/*
+	 * notes -- maybe just leave bi_idx alone. assume identical mapping
+	 * for the clone
+	 */
+	bio->bi_vcnt = bio_src->bi_vcnt;
+	bio->bi_size = bio_src->bi_size;
+	bio_phys_segments(q, bio);
+	bio_hw_segments(q, bio);
+}
+
+/**
+ *	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, unsigned int __nocast gfp_mask)
+{
+	struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, fs_bio_set);
+
+	if (b)
+		__bio_clone(b, bio);
+
+	return b;
+}
+
+/**
+ *	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)
+{
+	request_queue_t *q = bdev_get_queue(bdev);
+	int nr_pages;
+
+	nr_pages = ((q->max_sectors << 9) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if (nr_pages > q->max_phys_segments)
+		nr_pages = q->max_phys_segments;
+	if (nr_pages > q->max_hw_segments)
+		nr_pages = q->max_hw_segments;
+
+	return nr_pages;
+}
+
+static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page
+			  *page, unsigned int len, unsigned int offset)
+{
+	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_vcnt >= bio->bi_max_vecs)
+		return 0;
+
+	if (((bio->bi_size + len) >> 9) > q->max_sectors)
+		return 0;
+
+	/*
+	 * we might lose a segment or two here, but rather that than
+	 * make this too complex.
+	 */
+
+	while (bio->bi_phys_segments >= q->max_phys_segments
+	       || bio->bi_hw_segments >= q->max_hw_segments
+	       || BIOVEC_VIRT_OVERSIZE(bio->bi_size)) {
+
+		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) {
+		/*
+		 * merge_bvec_fn() returns number of bytes it can accept
+		 * at this offset
+		 */
+		if (q->merge_bvec_fn(q, bio, bvec) < 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) ||
+	    BIOVEC_VIRT_MERGEABLE(bvec-1, bvec)))
+		bio->bi_flags &= ~(1 << BIO_SEG_VALID);
+
+	bio->bi_vcnt++;
+	bio->bi_phys_segments++;
+	bio->bi_hw_segments++;
+	bio->bi_size += len;
+	return len;
+}
+
+/**
+ *	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
+ *      smaller than 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)
+{
+	return __bio_add_page(bdev_get_queue(bio->bi_bdev), bio, page,
+			      len, offset);
+}
+
+struct bio_map_data {
+	struct bio_vec *iovecs;
+	void __user *userptr;
+};
+
+static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio)
+{
+	memcpy(bmd->iovecs, bio->bi_io_vec, sizeof(struct bio_vec) * bio->bi_vcnt);
+	bio->bi_private = bmd;
+}
+
+static void bio_free_map_data(struct bio_map_data *bmd)
+{
+	kfree(bmd->iovecs);
+	kfree(bmd);
+}
+
+static struct bio_map_data *bio_alloc_map_data(int nr_segs)
+{
+	struct bio_map_data *bmd = kmalloc(sizeof(*bmd), GFP_KERNEL);
+
+	if (!bmd)
+		return NULL;
+
+	bmd->iovecs = kmalloc(sizeof(struct bio_vec) * nr_segs, GFP_KERNEL);
+	if (bmd->iovecs)
+		return bmd;
+
+	kfree(bmd);
+	return NULL;
+}
+
+/**
+ *	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;
+	const int read = bio_data_dir(bio) == READ;
+	struct bio_vec *bvec;
+	int i, ret = 0;
+
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		char *addr = page_address(bvec->bv_page);
+		unsigned int len = bmd->iovecs[i].bv_len;
+
+		if (read && !ret && copy_to_user(bmd->userptr, addr, len))
+			ret = -EFAULT;
+
+		__free_page(bvec->bv_page);
+		bmd->userptr += len;
+	}
+	bio_free_map_data(bmd);
+	bio_put(bio);
+	return ret;
+}
+
+/**
+ *	bio_copy_user	-	copy user data to bio
+ *	@q: destination block queue
+ *	@uaddr: start of user address
+ *	@len: length in bytes
+ *	@write_to_vm: bool indicating writing to pages or not
+ *
+ *	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(request_queue_t *q, unsigned long uaddr,
+			  unsigned int len, int write_to_vm)
+{
+	unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	unsigned long start = uaddr >> PAGE_SHIFT;
+	struct bio_map_data *bmd;
+	struct bio_vec *bvec;
+	struct page *page;
+	struct bio *bio;
+	int i, ret;
+
+	bmd = bio_alloc_map_data(end - start);
+	if (!bmd)
+		return ERR_PTR(-ENOMEM);
+
+	bmd->userptr = (void __user *) uaddr;
+
+	ret = -ENOMEM;
+	bio = bio_alloc(GFP_KERNEL, end - start);
+	if (!bio)
+		goto out_bmd;
+
+	bio->bi_rw |= (!write_to_vm << BIO_RW);
+
+	ret = 0;
+	while (len) {
+		unsigned int bytes = PAGE_SIZE;
+
+		if (bytes > len)
+			bytes = len;
+
+		page = alloc_page(q->bounce_gfp | GFP_KERNEL);
+		if (!page) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		if (__bio_add_page(q, bio, page, bytes, 0) < bytes) {
+			ret = -EINVAL;
+			break;
+		}
+
+		len -= bytes;
+	}
+
+	if (ret)
+		goto cleanup;
+
+	/*
+	 * success
+	 */
+	if (!write_to_vm) {
+		char __user *p = (char __user *) uaddr;
+
+		/*
+		 * for a write, copy in data to kernel pages
+		 */
+		ret = -EFAULT;
+		bio_for_each_segment(bvec, bio, i) {
+			char *addr = page_address(bvec->bv_page);
+
+			if (copy_from_user(addr, p, bvec->bv_len))
+				goto cleanup;
+			p += bvec->bv_len;
+		}
+	}
+
+	bio_set_map_data(bmd, bio);
+	return bio;
+cleanup:
+	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);
+}
+
+static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
+				  unsigned long uaddr, unsigned int len,
+				  int write_to_vm)
+{
+	unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	unsigned long start = uaddr >> PAGE_SHIFT;
+	const int nr_pages = end - start;
+	int ret, offset, i;
+	struct page **pages;
+	struct bio *bio;
+
+	/*
+	 * transfer and buffer must be aligned to at least hardsector
+	 * size for now, in the future we can relax this restriction
+	 */
+	if ((uaddr & queue_dma_alignment(q)) || (len & queue_dma_alignment(q)))
+		return ERR_PTR(-EINVAL);
+
+	bio = bio_alloc(GFP_KERNEL, nr_pages);
+	if (!bio)
+		return ERR_PTR(-ENOMEM);
+
+	ret = -ENOMEM;
+	pages = kmalloc(nr_pages * sizeof(struct page *), GFP_KERNEL);
+	if (!pages)
+		goto out;
+
+	down_read(&current->mm->mmap_sem);
+	ret = get_user_pages(current, current->mm, uaddr, nr_pages,
+						write_to_vm, 0, pages, NULL);
+	up_read(&current->mm->mmap_sem);
+
+	if (ret < nr_pages)
+		goto out;
+
+	bio->bi_bdev = bdev;
+
+	offset = uaddr & ~PAGE_MASK;
+	for (i = 0; i < nr_pages; i++) {
+		unsigned int bytes = PAGE_SIZE - offset;
+
+		if (len <= 0)
+			break;
+
+		if (bytes > len)
+			bytes = len;
+
+		/*
+		 * sorry...
+		 */
+		if (__bio_add_page(q, bio, pages[i], bytes, offset) < bytes)
+			break;
+
+		len -= bytes;
+		offset = 0;
+	}
+
+	/*
+	 * release the pages we didn't map into the bio, if any
+	 */
+	while (i < nr_pages)
+		page_cache_release(pages[i++]);
+
+	kfree(pages);
+
+	/*
+	 * set data direction, and check if mapped pages need bouncing
+	 */
+	if (!write_to_vm)
+		bio->bi_rw |= (1 << BIO_RW);
+
+	bio->bi_flags |= (1 << BIO_USER_MAPPED);
+	return bio;
+out:
+	kfree(pages);
+	bio_put(bio);
+	return ERR_PTR(ret);
+}
+
+/**
+ *	bio_map_user	-	map user address into bio
+ *	@bdev: destination block device
+ *	@uaddr: start of user address
+ *	@len: length in bytes
+ *	@write_to_vm: bool indicating writing to pages or not
+ *
+ *	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(request_queue_t *q, struct block_device *bdev,
+			 unsigned long uaddr, unsigned int len, int write_to_vm)
+{
+	struct bio *bio;
+
+	bio = __bio_map_user(q, bdev, uaddr, len, write_to_vm);
+
+	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);
+
+	if (bio->bi_size == len)
+		return bio;
+
+	/*
+	 * don't support partial mappings
+	 */
+	bio_endio(bio, bio->bi_size, 0);
+	bio_unmap_user(bio);
+	return ERR_PTR(-EINVAL);
+}
+
+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);
+}
+
+/*
+ * 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(void *data);
+
+static DECLARE_WORK(bio_dirty_work, bio_dirty_fn, NULL);
+static DEFINE_SPINLOCK(bio_dirty_lock);
+static struct bio *bio_dirty_list;
+
+/*
+ * This runs in process context
+ */
+static void bio_dirty_fn(void *data)
+{
+	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);
+	}
+}
+
+/**
+ * bio_endio - end I/O on a bio
+ * @bio:	bio
+ * @bytes_done:	number of bytes completed
+ * @error:	error, if any
+ *
+ * Description:
+ *   bio_endio() will end I/O on @bytes_done number of bytes. This may be
+ *   just a partial part of the bio, or it may be the whole bio. bio_endio()
+ *   is the preferred way to end I/O on a bio, it takes care of decrementing
+ *   bi_size and 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. Noone 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, unsigned int bytes_done, int error)
+{
+	if (error)
+		clear_bit(BIO_UPTODATE, &bio->bi_flags);
+
+	if (unlikely(bytes_done > bio->bi_size)) {
+		printk("%s: want %u bytes done, only %u left\n", __FUNCTION__,
+						bytes_done, bio->bi_size);
+		bytes_done = bio->bi_size;
+	}
+
+	bio->bi_size -= bytes_done;
+	bio->bi_sector += (bytes_done >> 9);
+
+	if (bio->bi_end_io)
+		bio->bi_end_io(bio, bytes_done, error);
+}
+
+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, master->bi_size, bp->error);
+		mempool_free(bp, bp->bio2.bi_private);
+	}
+}
+
+static int bio_pair_end_1(struct bio * bi, unsigned int done, int err)
+{
+	struct bio_pair *bp = container_of(bi, struct bio_pair, bio1);
+
+	if (err)
+		bp->error = err;
+
+	if (bi->bi_size)
+		return 1;
+
+	bio_pair_release(bp);
+	return 0;
+}
+
+static int bio_pair_end_2(struct bio * bi, unsigned int done, int err)
+{
+	struct bio_pair *bp = container_of(bi, struct bio_pair, bio2);
+
+	if (err)
+		bp->error = err;
+
+	if (bi->bi_size)
+		return 1;
+
+	bio_pair_release(bp);
+	return 0;
+}
+
+/*
+ * split a bio - only worry about a bio with a single page
+ * in it's iovec
+ */
+struct bio_pair *bio_split(struct bio *bi, mempool_t *pool, int first_sectors)
+{
+	struct bio_pair *bp = mempool_alloc(pool, GFP_NOIO);
+
+	if (!bp)
+		return bp;
+
+	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_end_io = bio_pair_end_1;
+	bp->bio2.bi_end_io = bio_pair_end_2;
+
+	bp->bio1.bi_private = bi;
+	bp->bio2.bi_private = pool;
+
+	return bp;
+}
+
+static void *bio_pair_alloc(unsigned int __nocast gfp_flags, void *data)
+{
+	return kmalloc(sizeof(struct bio_pair), gfp_flags);
+}
+
+static void bio_pair_free(void *bp, void *data)
+{
+	kfree(bp);
+}
+
+
+/*
+ * 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, int scale)
+{
+	int i;
+
+	for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+		struct biovec_slab *bp = bvec_slabs + i;
+		mempool_t **bvp = bs->bvec_pools + i;
+
+		if (i >= scale)
+			pool_entries >>= 1;
+
+		*bvp = mempool_create(pool_entries, mempool_alloc_slab,
+					mempool_free_slab, bp->slab);
+		if (!*bvp)
+			return -ENOMEM;
+	}
+	return 0;
+}
+
+static void biovec_free_pools(struct bio_set *bs)
+{
+	int i;
+
+	for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+		mempool_t *bvp = bs->bvec_pools[i];
+
+		if (bvp)
+			mempool_destroy(bvp);
+	}
+
+}
+
+void bioset_free(struct bio_set *bs)
+{
+	if (bs->bio_pool)
+		mempool_destroy(bs->bio_pool);
+
+	biovec_free_pools(bs);
+
+	kfree(bs);
+}
+
+struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size, int scale)
+{
+	struct bio_set *bs = kmalloc(sizeof(*bs), GFP_KERNEL);
+
+	if (!bs)
+		return NULL;
+
+	memset(bs, 0, sizeof(*bs));
+	bs->bio_pool = mempool_create(bio_pool_size, mempool_alloc_slab,
+			mempool_free_slab, bio_slab);
+
+	if (!bs->bio_pool)
+		goto bad;
+
+	if (!biovec_create_pools(bs, bvec_pool_size, scale))
+		return bs;
+
+bad:
+	bioset_free(bs);
+	return NULL;
+}
+
+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;
+
+		size = bvs->nr_vecs * sizeof(struct bio_vec);
+		bvs->slab = kmem_cache_create(bvs->name, size, 0,
+                                SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+	}
+}
+
+static int __init init_bio(void)
+{
+	int megabytes, bvec_pool_entries;
+	int scale = BIOVEC_NR_POOLS;
+
+	bio_slab = kmem_cache_create("bio", sizeof(struct bio), 0,
+				SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+
+	biovec_init_slabs();
+
+	megabytes = nr_free_pages() >> (20 - PAGE_SHIFT);
+
+	/*
+	 * find out where to start scaling
+	 */
+	if (megabytes <= 16)
+		scale = 0;
+	else if (megabytes <= 32)
+		scale = 1;
+	else if (megabytes <= 64)
+		scale = 2;
+	else if (megabytes <= 96)
+		scale = 3;
+	else if (megabytes <= 128)
+		scale = 4;
+
+	/*
+	 * scale number of entries
+	 */
+	bvec_pool_entries = megabytes * 2;
+	if (bvec_pool_entries > 256)
+		bvec_pool_entries = 256;
+
+	fs_bio_set = bioset_create(BIO_POOL_SIZE, bvec_pool_entries, scale);
+	if (!fs_bio_set)
+		panic("bio: can't allocate bios\n");
+
+	bio_split_pool = mempool_create(BIO_SPLIT_ENTRIES,
+				bio_pair_alloc, bio_pair_free, NULL);
+	if (!bio_split_pool)
+		panic("bio: can't create split pool\n");
+
+	return 0;
+}
+
+subsys_initcall(init_bio);
+
+EXPORT_SYMBOL(bio_alloc);
+EXPORT_SYMBOL(bio_put);
+EXPORT_SYMBOL(bio_endio);
+EXPORT_SYMBOL(bio_init);
+EXPORT_SYMBOL(__bio_clone);
+EXPORT_SYMBOL(bio_clone);
+EXPORT_SYMBOL(bio_phys_segments);
+EXPORT_SYMBOL(bio_hw_segments);
+EXPORT_SYMBOL(bio_add_page);
+EXPORT_SYMBOL(bio_get_nr_vecs);
+EXPORT_SYMBOL(bio_map_user);
+EXPORT_SYMBOL(bio_unmap_user);
+EXPORT_SYMBOL(bio_pair_release);
+EXPORT_SYMBOL(bio_split);
+EXPORT_SYMBOL(bio_split_pool);
+EXPORT_SYMBOL(bio_copy_user);
+EXPORT_SYMBOL(bio_uncopy_user);
+EXPORT_SYMBOL(bioset_create);
+EXPORT_SYMBOL(bioset_free);
+EXPORT_SYMBOL(bio_alloc_bioset);