block: move bio.c and bio-integrity.c from fs/ to block/

They really belong in block/, especially now since it's not in
drivers/block/ anymore. Additionally, the get_maintainer script
gets it wrong when in fs/.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2038 insertions, 0 deletions

diff --git a/block/bio.c b/block/bio.c
new file mode 100644
index 000000000000..96d28eee8a1e
--- /dev/null
+++ b/block/bio.c
@@ -0,0 +1,2038 @@
+/*
+ * 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/uio.h>
+#include <linux/iocontext.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/mempool.h>
+#include <linux/workqueue.h>
+#include <linux/cgroup.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
+
+/*
+ * 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;
+EXPORT_SYMBOL(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, *new_bio_slabs;
+	unsigned int new_bio_slab_max;
+	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) {
+		new_bio_slab_max = bio_slab_max << 1;
+		new_bio_slabs = krealloc(bio_slabs,
+					 new_bio_slab_max * sizeof(struct bio_slab),
+					 GFP_KERNEL);
+		if (!new_bio_slabs)
+			goto out_unlock;
+		bio_slab_max = new_bio_slab_max;
+		bio_slabs = new_bio_slabs;
+	}
+	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;
+
+	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(mempool_t *pool, struct bio_vec *bv, unsigned int idx)
+{
+	BIO_BUG_ON(idx >= BIOVEC_NR_POOLS);
+
+	if (idx == BIOVEC_MAX_IDX)
+		mempool_free(bv, pool);
+	else {
+		struct biovec_slab *bvs = bvec_slabs + idx;
+
+		kmem_cache_free(bvs->slab, bv);
+	}
+}
+
+struct bio_vec *bvec_alloc(gfp_t gfp_mask, int nr, unsigned long *idx,
+			   mempool_t *pool)
+{
+	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(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;
+}
+
+static void __bio_free(struct bio *bio)
+{
+	bio_disassociate_task(bio);
+
+	if (bio_integrity(bio))
+		bio_integrity_free(bio);
+}
+
+static void bio_free(struct bio *bio)
+{
+	struct bio_set *bs = bio->bi_pool;
+	void *p;
+
+	__bio_free(bio);
+
+	if (bs) {
+		if (bio_flagged(bio, BIO_OWNS_VEC))
+			bvec_free(bs->bvec_pool, bio->bi_io_vec, BIO_POOL_IDX(bio));
+
+		/*
+		 * If we have front padding, adjust the bio pointer before freeing
+		 */
+		p = bio;
+		p -= bs->front_pad;
+
+		mempool_free(p, bs->bio_pool);
+	} else {
+		/* Bio was allocated by bio_kmalloc() */
+		kfree(bio);
+	}
+}
+
+void bio_init(struct bio *bio)
+{
+	memset(bio, 0, sizeof(*bio));
+	bio->bi_flags = 1 << BIO_UPTODATE;
+	atomic_set(&bio->bi_remaining, 1);
+	atomic_set(&bio->bi_cnt, 1);
+}
+EXPORT_SYMBOL(bio_init);
+
+/**
+ * bio_reset - reinitialize a bio
+ * @bio:	bio to reset
+ *
+ * Description:
+ *   After calling bio_reset(), @bio will be in the same state as a freshly
+ *   allocated bio returned bio bio_alloc_bioset() - the only fields that are
+ *   preserved are the ones that are initialized by bio_alloc_bioset(). See
+ *   comment in struct bio.
+ */
+void bio_reset(struct bio *bio)
+{
+	unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
+
+	__bio_free(bio);
+
+	memset(bio, 0, BIO_RESET_BYTES);
+	bio->bi_flags = flags|(1 << BIO_UPTODATE);
+	atomic_set(&bio->bi_remaining, 1);
+}
+EXPORT_SYMBOL(bio_reset);
+
+static void bio_chain_endio(struct bio *bio, int error)
+{
+	bio_endio(bio->bi_private, error);
+	bio_put(bio);
+}
+
+/**
+ * bio_chain - chain bio completions
+ * @bio: the target bio
+ * @parent: the @bio's parent bio
+ *
+ * The caller won't have a bi_end_io called when @bio completes - instead,
+ * @parent's bi_end_io won't be called until both @parent and @bio have
+ * completed; the chained bio will also be freed when it completes.
+ *
+ * The caller must not set bi_private or bi_end_io in @bio.
+ */
+void bio_chain(struct bio *bio, struct bio *parent)
+{
+	BUG_ON(bio->bi_private || bio->bi_end_io);
+
+	bio->bi_private = parent;
+	bio->bi_end_io	= bio_chain_endio;
+	atomic_inc(&parent->bi_remaining);
+}
+EXPORT_SYMBOL(bio_chain);
+
+static void bio_alloc_rescue(struct work_struct *work)
+{
+	struct bio_set *bs = container_of(work, struct bio_set, rescue_work);
+	struct bio *bio;
+
+	while (1) {
+		spin_lock(&bs->rescue_lock);
+		bio = bio_list_pop(&bs->rescue_list);
+		spin_unlock(&bs->rescue_lock);
+
+		if (!bio)
+			break;
+
+		generic_make_request(bio);
+	}
+}
+
+static void punt_bios_to_rescuer(struct bio_set *bs)
+{
+	struct bio_list punt, nopunt;
+	struct bio *bio;
+
+	/*
+	 * In order to guarantee forward progress we must punt only bios that
+	 * were allocated from this bio_set; otherwise, if there was a bio on
+	 * there for a stacking driver higher up in the stack, processing it
+	 * could require allocating bios from this bio_set, and doing that from
+	 * our own rescuer would be bad.
+	 *
+	 * Since bio lists are singly linked, pop them all instead of trying to
+	 * remove from the middle of the list:
+	 */
+
+	bio_list_init(&punt);
+	bio_list_init(&nopunt);
+
+	while ((bio = bio_list_pop(current->bio_list)))
+		bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
+
+	*current->bio_list = nopunt;
+
+	spin_lock(&bs->rescue_lock);
+	bio_list_merge(&bs->rescue_list, &punt);
+	spin_unlock(&bs->rescue_lock);
+
+	queue_work(bs->rescue_workqueue, &bs->rescue_work);
+}
+
+/**
+ * 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:
+ *   If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is
+ *   backed by the @bs's mempool.
+ *
+ *   When @bs is not NULL, 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 deadlocks under memory pressure.
+ *
+ *   Note that when running under generic_make_request() (i.e. any block
+ *   driver), bios are not submitted until after you return - see the code in
+ *   generic_make_request() that converts recursion into iteration, to prevent
+ *   stack overflows.
+ *
+ *   This would normally mean allocating multiple bios under
+ *   generic_make_request() would be susceptible to deadlocks, but we have
+ *   deadlock avoidance code that resubmits any blocked bios from a rescuer
+ *   thread.
+ *
+ *   However, we do not guarantee forward progress for allocations from other
+ *   mempools. Doing multiple allocations from the same mempool under
+ *   generic_make_request() should be avoided - instead, use bio_set's front_pad
+ *   for per bio allocations.
+ *
+ *   RETURNS:
+ *   Pointer to new bio on success, NULL on failure.
+ */
+struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
+{
+	gfp_t saved_gfp = gfp_mask;
+	unsigned front_pad;
+	unsigned inline_vecs;
+	unsigned long idx = BIO_POOL_NONE;
+	struct bio_vec *bvl = NULL;
+	struct bio *bio;
+	void *p;
+
+	if (!bs) {
+		if (nr_iovecs > UIO_MAXIOV)
+			return NULL;
+
+		p = kmalloc(sizeof(struct bio) +
+			    nr_iovecs * sizeof(struct bio_vec),
+			    gfp_mask);
+		front_pad = 0;
+		inline_vecs = nr_iovecs;
+	} else {
+		/*
+		 * generic_make_request() converts recursion to iteration; this
+		 * means if we're running beneath it, any bios we allocate and
+		 * submit will not be submitted (and thus freed) until after we
+		 * return.
+		 *
+		 * This exposes us to a potential deadlock if we allocate
+		 * multiple bios from the same bio_set() while running
+		 * underneath generic_make_request(). If we were to allocate
+		 * multiple bios (say a stacking block driver that was splitting
+		 * bios), we would deadlock if we exhausted the mempool's
+		 * reserve.
+		 *
+		 * We solve this, and guarantee forward progress, with a rescuer
+		 * workqueue per bio_set. If we go to allocate and there are
+		 * bios on current->bio_list, we first try the allocation
+		 * without __GFP_WAIT; if that fails, we punt those bios we
+		 * would be blocking to the rescuer workqueue before we retry
+		 * with the original gfp_flags.
+		 */
+
+		if (current->bio_list && !bio_list_empty(current->bio_list))
+			gfp_mask &= ~__GFP_WAIT;
+
+		p = mempool_alloc(bs->bio_pool, gfp_mask);
+		if (!p && gfp_mask != saved_gfp) {
+			punt_bios_to_rescuer(bs);
+			gfp_mask = saved_gfp;
+			p = mempool_alloc(bs->bio_pool, gfp_mask);
+		}
+
+		front_pad = bs->front_pad;
+		inline_vecs = BIO_INLINE_VECS;
+	}
+
+	if (unlikely(!p))
+		return NULL;
+
+	bio = p + front_pad;
+	bio_init(bio);
+
+	if (nr_iovecs > inline_vecs) {
+		bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
+		if (!bvl && gfp_mask != saved_gfp) {
+			punt_bios_to_rescuer(bs);
+			gfp_mask = saved_gfp;
+			bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
+		}
+
+		if (unlikely(!bvl))
+			goto err_free;
+
+		bio->bi_flags |= 1 << BIO_OWNS_VEC;
+	} else if (nr_iovecs) {
+		bvl = bio->bi_inline_vecs;
+	}
+
+	bio->bi_pool = bs;
+	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);
+
+void zero_fill_bio(struct bio *bio)
+{
+	unsigned long flags;
+	struct bio_vec bv;
+	struct bvec_iter iter;
+
+	bio_for_each_segment(bv, bio, iter) {
+		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_free(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_fast - clone a bio that shares the original bio's biovec
+ * 	@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.
+ *
+ * 	Caller must ensure that @bio_src is not freed before @bio.
+ */
+void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
+{
+	BUG_ON(bio->bi_pool && BIO_POOL_IDX(bio) != BIO_POOL_NONE);
+
+	/*
+	 * 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_bdev = bio_src->bi_bdev;
+	bio->bi_flags |= 1 << BIO_CLONED;
+	bio->bi_rw = bio_src->bi_rw;
+	bio->bi_iter = bio_src->bi_iter;
+	bio->bi_io_vec = bio_src->bi_io_vec;
+}
+EXPORT_SYMBOL(__bio_clone_fast);
+
+/**
+ *	bio_clone_fast - clone a bio that shares the original bio's biovec
+ *	@bio: bio to clone
+ *	@gfp_mask: allocation priority
+ *	@bs: bio_set to allocate from
+ *
+ * 	Like __bio_clone_fast, only also allocates the returned bio
+ */
+struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
+{
+	struct bio *b;
+
+	b = bio_alloc_bioset(gfp_mask, 0, bs);
+	if (!b)
+		return NULL;
+
+	__bio_clone_fast(b, bio);
+
+	if (bio_integrity(bio)) {
+		int ret;
+
+		ret = bio_integrity_clone(b, bio, gfp_mask);
+
+		if (ret < 0) {
+			bio_put(b);
+			return NULL;
+		}
+	}
+
+	return b;
+}
+EXPORT_SYMBOL(bio_clone_fast);
+
+/**
+ * 	bio_clone_bioset - clone a bio
+ * 	@bio_src: bio to clone
+ *	@gfp_mask: allocation priority
+ *	@bs: bio_set to allocate from
+ *
+ *	Clone bio. Caller will own the returned bio, but not the actual data it
+ *	points to. Reference count of returned bio will be one.
+ */
+struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
+			     struct bio_set *bs)
+{
+	struct bvec_iter iter;
+	struct bio_vec bv;
+	struct bio *bio;
+
+	/*
+	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
+	 * bio_src->bi_io_vec to bio->bi_io_vec.
+	 *
+	 * We can't do that anymore, because:
+	 *
+	 *  - The point of cloning the biovec is to produce a bio with a biovec
+	 *    the caller can modify: bi_idx and bi_bvec_done should be 0.
+	 *
+	 *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
+	 *    we tried to clone the whole thing bio_alloc_bioset() would fail.
+	 *    But the clone should succeed as long as the number of biovecs we
+	 *    actually need to allocate is fewer than BIO_MAX_PAGES.
+	 *
+	 *  - Lastly, bi_vcnt should not be looked at or relied upon by code
+	 *    that does not own the bio - reason being drivers don't use it for
+	 *    iterating over the biovec anymore, so expecting it to be kept up
+	 *    to date (i.e. for clones that share the parent biovec) is just
+	 *    asking for trouble and would force extra work on
+	 *    __bio_clone_fast() anyways.
+	 */
+
+	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
+	if (!bio)
+		return NULL;
+
+	bio->bi_bdev		= bio_src->bi_bdev;
+	bio->bi_rw		= bio_src->bi_rw;
+	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
+	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
+
+	if (bio->bi_rw & REQ_DISCARD)
+		goto integrity_clone;
+
+	if (bio->bi_rw & REQ_WRITE_SAME) {
+		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
+		goto integrity_clone;
+	}
+
+	bio_for_each_segment(bv, bio_src, iter)
+		bio->bi_io_vec[bio->bi_vcnt++] = bv;
+
+integrity_clone:
+	if (bio_integrity(bio_src)) {
+		int ret;
+
+		ret = bio_integrity_clone(bio, bio_src, gfp_mask);
+		if (ret < 0) {
+			bio_put(bio);
+			return NULL;
+		}
+	}
+
+	return bio;
+}
+EXPORT_SYMBOL(bio_clone_bioset);
+
+/**
+ *	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 = min_t(unsigned,
+		     queue_max_segments(q),
+		     queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);
+
+	return min_t(unsigned, nr_pages, BIO_MAX_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 int 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_iter.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_iter.bi_sector,
+					.bi_size = bio->bi_iter.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_iter.bi_sector,
+			.bi_size = bio->bi_iter.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_iter.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 submit_bio_ret {
+	struct completion event;
+	int error;
+};
+
+static void submit_bio_wait_endio(struct bio *bio, int error)
+{
+	struct submit_bio_ret *ret = bio->bi_private;
+
+	ret->error = error;
+	complete(&ret->event);
+}
+
+/**
+ * submit_bio_wait - submit a bio, and wait until it completes
+ * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
+ * @bio: The &struct bio which describes the I/O
+ *
+ * Simple wrapper around submit_bio(). Returns 0 on success, or the error from
+ * bio_endio() on failure.
+ */
+int submit_bio_wait(int rw, struct bio *bio)
+{
+	struct submit_bio_ret ret;
+
+	rw |= REQ_SYNC;
+	init_completion(&ret.event);
+	bio->bi_private = &ret;
+	bio->bi_end_io = submit_bio_wait_endio;
+	submit_bio(rw, bio);
+	wait_for_completion(&ret.event);
+
+	return ret.error;
+}
+EXPORT_SYMBOL(submit_bio_wait);
+
+/**
+ * bio_advance - increment/complete a bio by some number of bytes
+ * @bio:	bio to advance
+ * @bytes:	number of bytes to complete
+ *
+ * This updates bi_sector, bi_size and bi_idx; if the number of bytes to
+ * complete doesn't align with a bvec boundary, then bv_len and bv_offset will
+ * be updated on the last bvec as well.
+ *
+ * @bio will then represent the remaining, uncompleted portion of the io.
+ */
+void bio_advance(struct bio *bio, unsigned bytes)
+{
+	if (bio_integrity(bio))
+		bio_integrity_advance(bio, bytes);
+
+	bio_advance_iter(bio, &bio->bi_iter, bytes);
+}
+EXPORT_SYMBOL(bio_advance);
+
+/**
+ * bio_alloc_pages - allocates a single page for each bvec in a bio
+ * @bio: bio to allocate pages for
+ * @gfp_mask: flags for allocation
+ *
+ * Allocates pages up to @bio->bi_vcnt.
+ *
+ * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
+ * freed.
+ */
+int bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
+{
+	int i;
+	struct bio_vec *bv;
+
+	bio_for_each_segment_all(bv, bio, i) {
+		bv->bv_page = alloc_page(gfp_mask);
+		if (!bv->bv_page) {
+			while (--bv >= bio->bi_io_vec)
+				__free_page(bv->bv_page);
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(bio_alloc_pages);
+
+/**
+ * bio_copy_data - copy contents of data buffers from one chain of bios to
+ * another
+ * @src: source bio list
+ * @dst: destination bio list
+ *
+ * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats
+ * @src and @dst as linked lists of bios.
+ *
+ * Stops when it reaches the end of either @src or @dst - that is, copies
+ * min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).
+ */
+void bio_copy_data(struct bio *dst, struct bio *src)
+{
+	struct bvec_iter src_iter, dst_iter;
+	struct bio_vec src_bv, dst_bv;
+	void *src_p, *dst_p;
+	unsigned bytes;
+
+	src_iter = src->bi_iter;
+	dst_iter = dst->bi_iter;
+
+	while (1) {
+		if (!src_iter.bi_size) {
+			src = src->bi_next;
+			if (!src)
+				break;
+
+			src_iter = src->bi_iter;
+		}
+
+		if (!dst_iter.bi_size) {
+			dst = dst->bi_next;
+			if (!dst)
+				break;
+
+			dst_iter = dst->bi_iter;
+		}
+
+		src_bv = bio_iter_iovec(src, src_iter);
+		dst_bv = bio_iter_iovec(dst, dst_iter);
+
+		bytes = min(src_bv.bv_len, dst_bv.bv_len);
+
+		src_p = kmap_atomic(src_bv.bv_page);
+		dst_p = kmap_atomic(dst_bv.bv_page);
+
+		memcpy(dst_p + dst_bv.bv_offset,
+		       src_p + src_bv.bv_offset,
+		       bytes);
+
+		kunmap_atomic(dst_p);
+		kunmap_atomic(src_p);
+
+		bio_advance_iter(src, &src_iter, bytes);
+		bio_advance_iter(dst, &dst_iter, bytes);
+	}
+}
+EXPORT_SYMBOL(bio_copy_data);
+
+struct bio_map_data {
+	int nr_sgvecs;
+	int is_our_pages;
+	struct sg_iovec sgvecs[];
+};
+
+static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
+			     const struct sg_iovec *iov, int iov_count,
+			     int is_our_pages)
+{
+	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 struct bio_map_data *bio_alloc_map_data(unsigned int iov_count,
+					       gfp_t gfp_mask)
+{
+	if (iov_count > UIO_MAXIOV)
+		return NULL;
+
+	return kmalloc(sizeof(struct bio_map_data) +
+		       sizeof(struct sg_iovec) * iov_count, gfp_mask);
+}
+
+static int __bio_copy_iov(struct bio *bio, const 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_all(bvec, bio, i) {
+		char *bv_addr = page_address(bvec->bv_page);
+		unsigned int bv_len = bvec->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;
+	struct bio_vec *bvec;
+	int ret = 0, i;
+
+	if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
+		/*
+		 * if we're in a workqueue, the request is orphaned, so
+		 * don't copy into a random user address space, just free.
+		 */
+		if (current->mm)
+			ret = __bio_copy_iov(bio, bmd->sgvecs, bmd->nr_sgvecs,
+					     bio_data_dir(bio) == READ,
+					     0, bmd->is_our_pages);
+		else if (bmd->is_our_pages)
+			bio_for_each_segment_all(bvec, bio, i)
+				__free_page(bvec->bv_page);
+	}
+	kfree(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,
+			      const 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(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, 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_all(bvec, bio, i)
+			__free_page(bvec->bv_page);
+
+	bio_put(bio);
+out_bmd:
+	kfree(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,
+				      const 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,
+			     const 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_all(bvec, bio, i) {
+		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_iter.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_all(bvec, bio, i) {
+		char *addr = page_address(bvec->bv_page);
+
+		if (read)
+			memcpy(p, addr, bvec->bv_len);
+
+		__free_page(bvec->bv_page);
+		p += bvec->bv_len;
+	}
+
+	kfree(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_all(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, flusher threads) 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;
+	int i;
+
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
+
+		if (page && !PageCompound(page))
+			set_page_dirty_lock(page);
+	}
+}
+
+static void bio_release_pages(struct bio *bio)
+{
+	struct bio_vec *bvec;
+	int i;
+
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->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;
+	int nr_clean_pages = 0;
+	int i;
+
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
+
+		if (PageDirty(page) || PageCompound(page)) {
+			page_cache_release(page);
+			bvec->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)
+{
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+
+	bio_for_each_segment(bvec, bi, iter)
+		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)
+{
+	while (bio) {
+		BUG_ON(atomic_read(&bio->bi_remaining) <= 0);
+
+		if (error)
+			clear_bit(BIO_UPTODATE, &bio->bi_flags);
+		else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+			error = -EIO;
+
+		if (!atomic_dec_and_test(&bio->bi_remaining))
+			return;
+
+		/*
+		 * Need to have a real endio function for chained bios,
+		 * otherwise various corner cases will break (like stacking
+		 * block devices that save/restore bi_end_io) - however, we want
+		 * to avoid unbounded recursion and blowing the stack. Tail call
+		 * optimization would handle this, but compiling with frame
+		 * pointers also disables gcc's sibling call optimization.
+		 */
+		if (bio->bi_end_io == bio_chain_endio) {
+			struct bio *parent = bio->bi_private;
+			bio_put(bio);
+			bio = parent;
+		} else {
+			if (bio->bi_end_io)
+				bio->bi_end_io(bio, error);
+			bio = NULL;
+		}
+	}
+}
+EXPORT_SYMBOL(bio_endio);
+
+/**
+ * bio_endio_nodec - end I/O on a bio, without decrementing bi_remaining
+ * @bio:	bio
+ * @error:	error, if any
+ *
+ * For code that has saved and restored bi_end_io; thing hard before using this
+ * function, probably you should've cloned the entire bio.
+ **/
+void bio_endio_nodec(struct bio *bio, int error)
+{
+	atomic_inc(&bio->bi_remaining);
+	bio_endio(bio, error);
+}
+EXPORT_SYMBOL(bio_endio_nodec);
+
+/**
+ * bio_split - split a bio
+ * @bio:	bio to split
+ * @sectors:	number of sectors to split from the front of @bio
+ * @gfp:	gfp mask
+ * @bs:		bio set to allocate from
+ *
+ * Allocates and returns a new bio which represents @sectors from the start of
+ * @bio, and updates @bio to represent the remaining sectors.
+ *
+ * The newly allocated bio will point to @bio's bi_io_vec; it is the caller's
+ * responsibility to ensure that @bio is not freed before the split.
+ */
+struct bio *bio_split(struct bio *bio, int sectors,
+		      gfp_t gfp, struct bio_set *bs)
+{
+	struct bio *split = NULL;
+
+	BUG_ON(sectors <= 0);
+	BUG_ON(sectors >= bio_sectors(bio));
+
+	split = bio_clone_fast(bio, gfp, bs);
+	if (!split)
+		return NULL;
+
+	split->bi_iter.bi_size = sectors << 9;
+
+	if (bio_integrity(split))
+		bio_integrity_trim(split, 0, sectors);
+
+	bio_advance(bio, split->bi_iter.bi_size);
+
+	return split;
+}
+EXPORT_SYMBOL(bio_split);
+
+/**
+ * bio_trim - trim a bio
+ * @bio:	bio to trim
+ * @offset:	number of sectors to trim from the front of @bio
+ * @size:	size we want to trim @bio to, in sectors
+ */
+void bio_trim(struct bio *bio, int offset, int size)
+{
+	/* 'bio' is a cloned bio which we need to trim to match
+	 * the given offset and size.
+	 */
+
+	size <<= 9;
+	if (offset == 0 && size == bio->bi_iter.bi_size)
+		return;
+
+	clear_bit(BIO_SEG_VALID, &bio->bi_flags);
+
+	bio_advance(bio, offset << 9);
+
+	bio->bi_iter.bi_size = size;
+}
+EXPORT_SYMBOL_GPL(bio_trim);
+
+/*
+ * create memory pools for biovec's in a bio_set.
+ * use the global biovec slabs created for general use.
+ */
+mempool_t *biovec_create_pool(int pool_entries)
+{
+	struct biovec_slab *bp = bvec_slabs + BIOVEC_MAX_IDX;
+
+	return mempool_create_slab_pool(pool_entries, bp->slab);
+}
+
+void bioset_free(struct bio_set *bs)
+{
+	if (bs->rescue_workqueue)
+		destroy_workqueue(bs->rescue_workqueue);
+
+	if (bs->bio_pool)
+		mempool_destroy(bs->bio_pool);
+
+	if (bs->bvec_pool)
+		mempool_destroy(bs->bvec_pool);
+
+	bioset_integrity_free(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;
+
+	spin_lock_init(&bs->rescue_lock);
+	bio_list_init(&bs->rescue_list);
+	INIT_WORK(&bs->rescue_work, bio_alloc_rescue);
+
+	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;
+
+	bs->bvec_pool = biovec_create_pool(pool_size);
+	if (!bs->bvec_pool)
+		goto bad;
+
+	bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0);
+	if (!bs->rescue_workqueue)
+		goto bad;
+
+	return bs;
+bad:
+	bioset_free(bs);
+	return NULL;
+}
+EXPORT_SYMBOL(bioset_create);
+
+#ifdef CONFIG_BLK_CGROUP
+/**
+ * bio_associate_current - associate a bio with %current
+ * @bio: target bio
+ *
+ * Associate @bio with %current if it hasn't been associated yet.  Block
+ * layer will treat @bio as if it were issued by %current no matter which
+ * task actually issues it.
+ *
+ * This function takes an extra reference of @task's io_context and blkcg
+ * which will be put when @bio is released.  The caller must own @bio,
+ * ensure %current->io_context exists, and is responsible for synchronizing
+ * calls to this function.
+ */
+int bio_associate_current(struct bio *bio)
+{
+	struct io_context *ioc;
+	struct cgroup_subsys_state *css;
+
+	if (bio->bi_ioc)
+		return -EBUSY;
+
+	ioc = current->io_context;
+	if (!ioc)
+		return -ENOENT;
+
+	/* acquire active ref on @ioc and associate */
+	get_io_context_active(ioc);
+	bio->bi_ioc = ioc;
+
+	/* associate blkcg if exists */
+	rcu_read_lock();
+	css = task_css(current, blkio_cgrp_id);
+	if (css && css_tryget(css))
+		bio->bi_css = css;
+	rcu_read_unlock();
+
+	return 0;
+}
+
+/**
+ * bio_disassociate_task - undo bio_associate_current()
+ * @bio: target bio
+ */
+void bio_disassociate_task(struct bio *bio)
+{
+	if (bio->bi_ioc) {
+		put_io_context(bio->bi_ioc);
+		bio->bi_ioc = NULL;
+	}
+	if (bio->bi_css) {
+		css_put(bio->bi_css);
+		bio->bi_css = NULL;
+	}
+}
+
+#endif /* CONFIG_BLK_CGROUP */
+
+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");
+
+	return 0;
+}
+subsys_initcall(init_bio);