bio.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2001 Jens Axboe <axboe@kernel.dk>
 */
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/bio-integrity.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 <linux/highmem.h>
#include <linux/blk-crypto.h>
#include <linux/xarray.h>
#include <linux/kmemleak.h>

#include <trace/events/block.h>
#include "blk.h"
#include "blk-rq-qos.h"
#include "blk-cgroup.h"

#define ALLOC_CACHE_THRESHOLD	16
#define ALLOC_CACHE_MAX		256

struct bio_alloc_cache {
	struct bio		*free_list;
	struct bio		*free_list_irq;
	unsigned int		nr;
	unsigned int		nr_irq;
};

#define BIO_INLINE_VECS 4

static struct biovec_slab {
	int nr_vecs;
	char *name;
	struct kmem_cache *slab;
} bvec_slabs[] __read_mostly = {
	{ .nr_vecs = 16, .name = "biovec-16" },
	{ .nr_vecs = 64, .name = "biovec-64" },
	{ .nr_vecs = 128, .name = "biovec-128" },
	{ .nr_vecs = BIO_MAX_VECS, .name = "biovec-max" },
};

static struct biovec_slab *biovec_slab(unsigned short nr_vecs)
{
	switch (nr_vecs) {
	/* smaller bios use inline vecs */
	case 5 ... 16:
		return &bvec_slabs[0];
	case 17 ... 64:
		return &bvec_slabs[1];
	case 65 ... 128:
		return &bvec_slabs[2];
	case 129 ... BIO_MAX_VECS:
		return &bvec_slabs[3];
	default:
		BUG();
		return NULL;
	}
}

/*
 * 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[12];
};
static DEFINE_MUTEX(bio_slab_lock);
static DEFINE_XARRAY(bio_slabs);

static struct bio_slab *create_bio_slab(unsigned int size)
{
	struct bio_slab *bslab = kzalloc_obj(*bslab);

	if (!bslab)
		return NULL;

	snprintf(bslab->name, sizeof(bslab->name), "bio-%d", size);
	bslab->slab = kmem_cache_create(bslab->name, size,
			ARCH_KMALLOC_MINALIGN,
			SLAB_HWCACHE_ALIGN | SLAB_TYPESAFE_BY_RCU, NULL);
	if (!bslab->slab)
		goto fail_alloc_slab;

	bslab->slab_ref = 1;
	bslab->slab_size = size;

	if (!xa_err(xa_store(&bio_slabs, size, bslab, GFP_KERNEL)))
		return bslab;

	kmem_cache_destroy(bslab->slab);

fail_alloc_slab:
	kfree(bslab);
	return NULL;
}

static inline unsigned int bs_bio_slab_size(struct bio_set *bs)
{
	return bs->front_pad + sizeof(struct bio) + bs->back_pad;
}

static inline void *bio_slab_addr(struct bio *bio)
{
	return (void *)bio - bio->bi_pool->front_pad;
}

static struct kmem_cache *bio_find_or_create_slab(struct bio_set *bs)
{
	unsigned int size = bs_bio_slab_size(bs);
	struct bio_slab *bslab;

	mutex_lock(&bio_slab_lock);
	bslab = xa_load(&bio_slabs, size);
	if (bslab)
		bslab->slab_ref++;
	else
		bslab = create_bio_slab(size);
	mutex_unlock(&bio_slab_lock);

	if (bslab)
		return bslab->slab;
	return NULL;
}

static void bio_put_slab(struct bio_set *bs)
{
	struct bio_slab *bslab = NULL;
	unsigned int slab_size = bs_bio_slab_size(bs);

	mutex_lock(&bio_slab_lock);

	bslab = xa_load(&bio_slabs, slab_size);
	if (WARN(!bslab, KERN_ERR "bio: unable to find slab!\n"))
		goto out;

	WARN_ON_ONCE(bslab->slab != bs->bio_slab);

	WARN_ON(!bslab->slab_ref);

	if (--bslab->slab_ref)
		goto out;

	xa_erase(&bio_slabs, slab_size);

	kmem_cache_destroy(bslab->slab);
	kfree(bslab);

out:
	mutex_unlock(&bio_slab_lock);
}

/*
 * Make the first allocation restricted and don't dump info on allocation
 * failures, since we'll fall back to the mempool in case of failure.
 */
static inline gfp_t try_alloc_gfp(gfp_t gfp)
{
	return (gfp & ~(__GFP_DIRECT_RECLAIM | __GFP_IO)) |
		__GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
}

void bio_uninit(struct bio *bio)
{
#ifdef CONFIG_BLK_CGROUP
	if (bio->bi_blkg) {
		blkg_put(bio->bi_blkg);
		bio->bi_blkg = NULL;
	}
#endif
	if (bio_integrity(bio))
		bio_integrity_free(bio);

	bio_crypt_free_ctx(bio);
}
EXPORT_SYMBOL(bio_uninit);

static void bio_free(struct bio *bio)
{
	struct bio_set *bs = bio->bi_pool;
	void *p = bio;

	WARN_ON_ONCE(!bs);
	WARN_ON_ONCE(bio->bi_max_vecs > BIO_MAX_VECS);

	bio_uninit(bio);
	if (bio->bi_max_vecs == BIO_MAX_VECS)
		mempool_free(bio->bi_io_vec, &bs->bvec_pool);
	else if (bio->bi_max_vecs > BIO_INLINE_VECS)
		kmem_cache_free(biovec_slab(bio->bi_max_vecs)->slab,
				bio->bi_io_vec);
	mempool_free(p - bs->front_pad, &bs->bio_pool);
}

/*
 * Users of this function have their own bio allocation. Subsequently,
 * they must remember to pair any call to bio_init() with bio_uninit()
 * when IO has completed, or when the bio is released.
 */
void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
	      unsigned short max_vecs, blk_opf_t opf)
{
	bio->bi_next = NULL;
	bio->bi_bdev = bdev;
	bio->bi_opf = opf;
	bio->bi_flags = 0;
	bio->bi_ioprio = 0;
	bio->bi_write_hint = 0;
	bio->bi_write_stream = 0;
	bio->bi_status = 0;
	bio->bi_bvec_gap_bit = 0;
	bio->bi_iter.bi_sector = 0;
	bio->bi_iter.bi_size = 0;
	bio->bi_iter.bi_idx = 0;
	bio->bi_iter.bi_offset = 0;
	bio->bi_end_io = NULL;
	bio->bi_private = NULL;
#ifdef CONFIG_BLK_CGROUP
	bio->bi_blkg = NULL;
	bio->issue_time_ns = 0;
	if (bdev)
		bio_associate_blkg(bio);
#ifdef CONFIG_BLK_CGROUP_IOCOST
	bio->bi_iocost_cost = 0;
#endif
#endif
#ifdef CONFIG_BLK_INLINE_ENCRYPTION
	bio->bi_crypt_context = NULL;
#endif
#ifdef CONFIG_BLK_DEV_INTEGRITY
	bio->bi_integrity = NULL;
#endif
	bio->bi_vcnt = 0;

	atomic_set(&bio->__bi_remaining, 1);
	atomic_set(&bio->__bi_cnt, 1);
	bio->bi_cookie = BLK_QC_T_NONE;

	bio->bi_max_vecs = max_vecs;
	bio->bi_io_vec = table;
	bio->bi_pool = NULL;
}
EXPORT_SYMBOL(bio_init);

/**
 * bio_reset - reinitialize a bio
 * @bio:	bio to reset
 * @bdev:	block device to use the bio for
 * @opf:	operation and flags for bio
 *
 * 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, struct block_device *bdev, blk_opf_t opf)
{
	struct bio_vec          *bv = bio->bi_io_vec;

	bio_uninit(bio);
	memset(bio, 0, BIO_RESET_BYTES);
	atomic_set(&bio->__bi_remaining, 1);
	bio->bi_io_vec = bv;
	bio->bi_bdev = bdev;
	if (bio->bi_bdev)
		bio_associate_blkg(bio);
	bio->bi_opf = opf;
}
EXPORT_SYMBOL(bio_reset);

/**
 * bio_reuse - reuse a bio with the payload left intact
 * @bio:	bio to reuse
 * @opf:	operation and flags for the next I/O
 *
 * Allow reusing an existing bio for another operation with all set up
 * fields including the payload, device and end_io handler left intact.
 *
 * Typically used when @bio is first used to read data which is then written
 * to another location without modification.  @bio must not be in-flight and
 * owned by the caller.  Can't be used for cloned bios.
 *
 * Note: Can't be used when @bio has integrity or blk-crypto contexts for now.
 * Feel free to add that support when you need it, though.
 */
void bio_reuse(struct bio *bio, blk_opf_t opf)
{
	unsigned short vcnt = bio->bi_vcnt, i;
	bio_end_io_t *end_io = bio->bi_end_io;
	void *private = bio->bi_private;

	WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
	WARN_ON_ONCE(bio_integrity(bio));
	WARN_ON_ONCE(bio_has_crypt_ctx(bio));

	bio_reset(bio, bio->bi_bdev, opf);
	for (i = 0; i < vcnt; i++)
		bio->bi_iter.bi_size += bio->bi_io_vec[i].bv_len;
	bio->bi_vcnt = vcnt;
	bio->bi_private = private;
	bio->bi_end_io = end_io;
}
EXPORT_SYMBOL_GPL(bio_reuse);

static struct bio *__bio_chain_endio(struct bio *bio)
{
	struct bio *parent = bio->bi_private;

	if (bio->bi_status && !parent->bi_status)
		parent->bi_status = bio->bi_status;
	bio_put(bio);
	return parent;
}

/*
 * This function should only be used as a flag and must never be called.
 * If execution reaches here, it indicates a serious programming error.
 */
static void bio_chain_endio(struct bio *bio)
{
	BUG();
}

/**
 * bio_chain - chain bio completions
 * @bio: the target bio
 * @parent: the parent bio of @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;
	bio_inc_remaining(parent);
}
EXPORT_SYMBOL(bio_chain);

/**
 * bio_chain_and_submit - submit a bio after chaining it to another one
 * @prev: bio to chain and submit
 * @new: bio to chain to
 *
 * If @prev is non-NULL, chain it to @new and submit it.
 *
 * Return: @new.
 */
struct bio *bio_chain_and_submit(struct bio *prev, struct bio *new)
{
	if (prev) {
		bio_chain(prev, new);
		submit_bio(prev);
	}
	return new;
}

struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
		unsigned int nr_pages, blk_opf_t opf, gfp_t gfp)
{
	return bio_chain_and_submit(bio, bio_alloc(bdev, nr_pages, opf, gfp));
}
EXPORT_SYMBOL_GPL(blk_next_bio);

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;

		submit_bio_noacct(bio);
	}
}

/*
 * submit_bio_noacct() 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 submit_bio_noacct().  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 by punting the bios on
 * current->bio_list to a per bio_set rescuer workqueue before blocking to wait
 * for elements being returned to the mempool.
 */
static void punt_bios_to_rescuer(struct bio_set *bs)
{
	struct bio_list punt, nopunt;
	struct bio *bio;

	if (!current->bio_list || !bs->rescue_workqueue)
		return;
	if (bio_list_empty(&current->bio_list[0]) &&
	    bio_list_empty(&current->bio_list[1]))
		return;

	/*
	 * 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[0])))
		bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
	current->bio_list[0] = nopunt;

	bio_list_init(&nopunt);
	while ((bio = bio_list_pop(&current->bio_list[1])))
		bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
	current->bio_list[1] = 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);
}

static void bio_alloc_irq_cache_splice(struct bio_alloc_cache *cache)
{
	unsigned long flags;

	/* cache->free_list must be empty */
	if (WARN_ON_ONCE(cache->free_list))
		return;

	local_irq_save(flags);
	cache->free_list = cache->free_list_irq;
	cache->free_list_irq = NULL;
	cache->nr += cache->nr_irq;
	cache->nr_irq = 0;
	local_irq_restore(flags);
}

static struct bio *bio_alloc_percpu_cache(struct bio_set *bs)
{
	struct bio_alloc_cache *cache;
	struct bio *bio;

	cache = per_cpu_ptr(bs->cache, get_cpu());
	if (!cache->free_list) {
		if (READ_ONCE(cache->nr_irq) >= ALLOC_CACHE_THRESHOLD)
			bio_alloc_irq_cache_splice(cache);
		if (!cache->free_list) {
			put_cpu();
			return NULL;
		}
	}
	bio = cache->free_list;
	cache->free_list = bio->bi_next;
	cache->nr--;
	put_cpu();
	bio->bi_pool = bs;

	kmemleak_alloc(bio_slab_addr(bio),
		       kmem_cache_size(bs->bio_slab), 1, GFP_NOIO);
	return bio;
}

/**
 * bio_alloc_bioset - allocate a bio for I/O
 * @bdev:	block device to allocate the bio for (can be %NULL)
 * @nr_vecs:	number of bvecs to pre-allocate
 * @opf:	operation and flags for bio
 * @gfp:	the GFP_* mask given to the slab allocator
 * @bs:		the bio_set to allocate from.
 *
 * Allocate a bio from the mempools in @bs.
 *
 * If %__GFP_DIRECT_RECLAIM 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 the general 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 submit_bio_noacct() (i.e. any block driver),
 * bios are not submitted until after you return - see the code in
 * submit_bio_noacct() that converts recursion into iteration, to prevent
 * stack overflows.
 *
 * This would normally mean allocating multiple bios under submit_bio_noacct()
 * 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
 * submit_bio_noacct() 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(struct block_device *bdev, unsigned short nr_vecs,
			     blk_opf_t opf, gfp_t gfp, struct bio_set *bs)
{
	struct bio_vec *bvecs = NULL;
	struct bio *bio = NULL;
	gfp_t saved_gfp = gfp;
	void *p;

	/* should not use nobvec bioset for nr_vecs > 0 */
	if (WARN_ON_ONCE(!mempool_initialized(&bs->bvec_pool) && nr_vecs > 0))
		return NULL;

	if (saved_gfp & __GFP_DIRECT_RECLAIM)
		gfp = try_alloc_gfp(gfp);
	if (bs->cache && nr_vecs <= BIO_INLINE_VECS) {
		/*
		 * Set REQ_ALLOC_CACHE even if no cached bio is available to
		 * return the allocated bio to the percpu cache when done.
		 */
		opf |= REQ_ALLOC_CACHE;
		bio = bio_alloc_percpu_cache(bs);
	} else {
		opf &= ~REQ_ALLOC_CACHE;
	}

	/*
	 * For a bioset without a percpu cache, or when the percpu cache was
	 * empty, try a slab allocation with optimistic GFP_ flags before
	 * falling back to the mempool.
	 */
	if (!bio) {
		p = kmem_cache_alloc(bs->bio_slab, gfp);
		if (p)
			bio = p + bs->front_pad;
	}

	if (bio && nr_vecs > BIO_INLINE_VECS) {
		struct biovec_slab *bvs = biovec_slab(nr_vecs);

		/*
		 * Upgrade nr_vecs to take full advantage of the allocation.
		 * We also rely on this in bio_free().
		 */
		nr_vecs = bvs->nr_vecs;
		bvecs = kmem_cache_alloc(bvs->slab, gfp);
		if (unlikely(!bvecs)) {
			kmem_cache_free(bs->bio_slab, p);
			bio = NULL;
		}
	}

	if (unlikely(!bio)) {
		/*
		 * Give up if we are not allow to sleep as non-blocking mempool
		 * allocations just go back to the slab allocation.
		 */
		if (!(saved_gfp & __GFP_DIRECT_RECLAIM))
			return NULL;

		punt_bios_to_rescuer(bs);

		/*
		 * Don't rob the mempools by returning to the per-CPU cache if
		 * we're tight on memory.
		 */
		opf &= ~REQ_ALLOC_CACHE;

		p = mempool_alloc(&bs->bio_pool, saved_gfp);
		bio = p + bs->front_pad;
		if (nr_vecs > BIO_INLINE_VECS) {
			nr_vecs = BIO_MAX_VECS;
			bvecs = mempool_alloc(&bs->bvec_pool, saved_gfp);
		}
	}

	if (nr_vecs && nr_vecs <= BIO_INLINE_VECS)
		bio_init_inline(bio, bdev, nr_vecs, opf);
	else
		bio_init(bio, bdev, bvecs, nr_vecs, opf);
	bio->bi_pool = bs;
	return bio;
}
EXPORT_SYMBOL(bio_alloc_bioset);

/**
 * bio_kmalloc - kmalloc a bio
 * @nr_vecs:	number of bio_vecs to allocate
 * @gfp_mask:   the GFP_* mask given to the slab allocator
 *
 * Use kmalloc to allocate a bio (including bvecs).  The bio must be initialized
 * using bio_init() before use.  To free a bio returned from this function use
 * kfree() after calling bio_uninit().  A bio returned from this function can
 * be reused by calling bio_uninit() before calling bio_init() again.
 *
 * Note that unlike bio_alloc() or bio_alloc_bioset() allocations from this
 * function are not backed by a mempool can fail.  Do not use this function
 * for allocations in the file system I/O path.
 *
 * Returns: Pointer to new bio on success, NULL on failure.
 */
struct bio *bio_kmalloc(unsigned short nr_vecs, gfp_t gfp_mask)
{
	struct bio *bio;

	if (nr_vecs > BIO_MAX_INLINE_VECS)
		return NULL;
	return kmalloc(sizeof(*bio) + nr_vecs * sizeof(struct bio_vec),
			gfp_mask);
}
EXPORT_SYMBOL(bio_kmalloc);

void zero_fill_bio(struct bio *bio)
{
	struct bio_vec bv;
	struct bvec_iter iter;

	bio_for_each_segment(bv, bio, iter)
		memzero_bvec(&bv);
}
EXPORT_SYMBOL(zero_fill_bio);

/**
 * bio_truncate - truncate the bio to small size of @new_size
 * @bio:	the bio to be truncated
 * @new_size:	new size for truncating the bio
 *
 * Description:
 *   Truncate the bio to new size of @new_size. If bio_op(bio) is
 *   REQ_OP_READ, zero the truncated part. This function should only
 *   be used for handling corner cases, such as bio eod.
 */
static void bio_truncate(struct bio *bio, unsigned new_size)
{
	struct bio_vec bv;
	struct bvec_iter iter;
	unsigned int done = 0;
	bool truncated = false;

	if (new_size >= bio->bi_iter.bi_size)
		return;

	if (bio_op(bio) != REQ_OP_READ)
		goto exit;

	bio_for_each_segment(bv, bio, iter) {
		if (done + bv.bv_len > new_size) {
			size_t offset;

			if (!truncated)
				offset = new_size - done;
			else
				offset = 0;
			memzero_page(bv.bv_page, bv.bv_offset + offset,
				  bv.bv_len - offset);
			truncated = true;
		}
		done += bv.bv_len;
	}

 exit:
	/*
	 * Don't touch bvec table here and make it really immutable, since
	 * fs bio user has to retrieve all pages via bio_for_each_segment_all
	 * in its .end_bio() callback.
	 *
	 * It is enough to truncate bio by updating .bi_size since we can make
	 * correct bvec with the updated .bi_size for drivers.
	 */
	bio->bi_iter.bi_size = new_size;
}

/**
 * guard_bio_eod - truncate a BIO to fit the block device
 * @bio:	bio to truncate
 *
 * This allows us to do IO even on the odd last sectors of a device, even if the
 * block size is some multiple of the physical sector size.
 *
 * We'll just truncate the bio to the size of the device, and clear the end of
 * the buffer head manually.  Truly out-of-range accesses will turn into actual
 * I/O errors, this only handles the "we need to be able to do I/O at the final
 * sector" case.
 */
void guard_bio_eod(struct bio *bio)
{
	sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);

	if (!maxsector)
		return;

	/*
	 * If the *whole* IO is past the end of the device,
	 * let it through, and the IO layer will turn it into
	 * an EIO.
	 */
	if (unlikely(bio->bi_iter.bi_sector >= maxsector))
		return;

	maxsector -= bio->bi_iter.bi_sector;
	if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
		return;

	bio_truncate(bio, maxsector << 9);
}

static int __bio_alloc_cache_prune(struct bio_alloc_cache *cache,
				   unsigned int nr)
{
	unsigned int i = 0;
	struct bio *bio;

	while ((bio = cache->free_list) != NULL) {
		cache->free_list = bio->bi_next;
		cache->nr--;
		kmemleak_alloc(bio_slab_addr(bio),
			       kmem_cache_size(bio->bi_pool->bio_slab),
			       1, GFP_KERNEL);
		bio_free(bio);
		if (++i == nr)
			break;
	}
	return i;
}

static void bio_alloc_cache_prune(struct bio_alloc_cache *cache,
				  unsigned int nr)
{
	nr -= __bio_alloc_cache_prune(cache, nr);
	if (!READ_ONCE(cache->free_list)) {
		bio_alloc_irq_cache_splice(cache);
		__bio_alloc_cache_prune(cache, nr);
	}
}

static int bio_cpu_dead(unsigned int cpu, struct hlist_node *node)
{
	struct bio_set *bs;

	bs = hlist_entry_safe(node, struct bio_set, cpuhp_dead);
	if (bs->cache) {
		struct bio_alloc_cache *cache = per_cpu_ptr(bs->cache, cpu);

		bio_alloc_cache_prune(cache, -1U);
	}
	return 0;
}

static void bio_alloc_cache_destroy(struct bio_set *bs)
{
	int cpu;

	if (!bs->cache)
		return;

	cpuhp_state_remove_instance_nocalls(CPUHP_BIO_DEAD, &bs->cpuhp_dead);
	for_each_possible_cpu(cpu) {
		struct bio_alloc_cache *cache;

		cache = per_cpu_ptr(bs->cache, cpu);
		bio_alloc_cache_prune(cache, -1U);
	}
	free_percpu(bs->cache);
	bs->cache = NULL;
}

static inline void bio_put_percpu_cache(struct bio *bio)
{
	struct bio_alloc_cache *cache;

	cache = per_cpu_ptr(bio->bi_pool->cache, get_cpu());
	if (READ_ONCE(cache->nr_irq) + cache->nr > ALLOC_CACHE_MAX)
		goto out_free;

	if (in_task()) {
		bio_uninit(bio);
		bio->bi_next = cache->free_list;
		/* Not necessary but helps not to iopoll already freed bios */
		bio->bi_bdev = NULL;
		cache->free_list = bio;
		cache->nr++;
		kmemleak_free(bio_slab_addr(bio));
	} else if (in_hardirq()) {
		lockdep_assert_irqs_disabled();

		bio_uninit(bio);
		bio->bi_next = cache->free_list_irq;
		cache->free_list_irq = bio;
		cache->nr_irq++;
		kmemleak_free(bio_slab_addr(bio));
	} else {
		goto out_free;
	}
	put_cpu();
	return;
out_free:
	put_cpu();
	bio_free(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)
{
	if (unlikely(bio_flagged(bio, BIO_REFFED))) {
		BUG_ON(!atomic_read(&bio->__bi_cnt));
		if (!atomic_dec_and_test(&bio->__bi_cnt))
			return;
	}
	if (bio->bi_opf & REQ_ALLOC_CACHE)
		bio_put_percpu_cache(bio);
	else
		bio_free(bio);
}
EXPORT_SYMBOL(bio_put);

static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
{
	bio_set_flag(bio, BIO_CLONED);
	bio->bi_ioprio = bio_src->bi_ioprio;
	bio->bi_write_hint = bio_src->bi_write_hint;
	bio->bi_write_stream = bio_src->bi_write_stream;
	bio->bi_bvec_gap_bit = bio_src->bi_bvec_gap_bit;
	bio->bi_iter = bio_src->bi_iter;
	bio->bi_io_vec = bio_src->bi_io_vec;

	if (bio->bi_bdev) {
		if (bio->bi_bdev == bio_src->bi_bdev &&
		    bio_flagged(bio_src, BIO_REMAPPED))
			bio_set_flag(bio, BIO_REMAPPED);
		bio_clone_blkg_association(bio, bio_src);
	}

	if (bio_crypt_clone(bio, bio_src, gfp) < 0)
		return -ENOMEM;
	if (bio_integrity(bio_src) &&
	    bio_integrity_clone(bio, bio_src, gfp) < 0)
		return -ENOMEM;
	return 0;
}

/**
 * bio_alloc_clone - clone a bio that shares the original bio's biovec
 * @bdev: block_device to clone onto
 * @bio_src: bio to clone from
 * @gfp: allocation priority
 * @bs: bio_set to allocate from
 *
 * Allocate a new bio that is a clone of @bio_src. This reuses the bio_vecs
 * pointed to by @bio_src->bi_io_vec, and clones the iterator pointing to
 * the current position in it.  The caller owns the returned bio, but not
 * the bio_vecs, and must ensure the bio is freed before the memory
 * pointed to by @bio_Src->bi_io_vecs.
 */
struct bio *bio_alloc_clone(struct block_device *bdev, struct bio *bio_src,
		gfp_t gfp, struct bio_set *bs)
{
	struct bio *bio;

	bio = bio_alloc_bioset(bdev, 0, bio_src->bi_opf, gfp, bs);
	if (!bio)
		return NULL;

	if (__bio_clone(bio, bio_src, gfp) < 0) {
		bio_put(bio);
		return NULL;
	}
	return bio;
}
EXPORT_SYMBOL(bio_alloc_clone);

/**
 * bio_init_clone - clone a bio that shares the original bio's biovec
 * @bdev: block_device to clone onto
 * @bio: bio to clone into
 * @bio_src: bio to clone from
 * @gfp: allocation priority
 *
 * Initialize a new bio in caller provided memory that is a clone of @bio_src.
 * The same bio_vecs reuse and bio lifetime rules as bio_alloc_clone() apply.
 */
int bio_init_clone(struct block_device *bdev, struct bio *bio,
		struct bio *bio_src, gfp_t gfp)
{
	int ret;

	bio_init(bio, bdev, NULL, 0, bio_src->bi_opf);
	ret = __bio_clone(bio, bio_src, gfp);
	if (ret)
		bio_uninit(bio);
	return ret;
}
EXPORT_SYMBOL(bio_init_clone);

/**
 * bio_full - check if the bio is full
 * @bio:	bio to check
 * @len:	length of one segment to be added
 *
 * Return true if @bio is full and one segment with @len bytes can't be
 * added to the bio, otherwise return false
 */
static inline bool bio_full(struct bio *bio, unsigned len)
{
	if (bio->bi_vcnt >= bio->bi_max_vecs)
		return true;
	if (bio->bi_iter.bi_size > BIO_MAX_SIZE - len)
		return true;
	return false;
}

static bool bvec_try_merge_page(struct bio_vec *bv, struct page *page,
		unsigned int len, unsigned int off)
{
	size_t bv_end = bv->bv_offset + bv->bv_len;
	phys_addr_t vec_end_addr = page_to_phys(bv->bv_page) + bv_end - 1;
	phys_addr_t page_addr = page_to_phys(page);

	if (vec_end_addr + 1 != page_addr + off)
		return false;
	if (xen_domain() && !xen_biovec_phys_mergeable(bv, page))
		return false;

	if ((vec_end_addr & PAGE_MASK) != ((page_addr + off) & PAGE_MASK)) {
		if (IS_ENABLED(CONFIG_KMSAN))
			return false;
		if (bv->bv_page + bv_end / PAGE_SIZE != page + off / PAGE_SIZE)
			return false;
	}

	bv->bv_len += len;
	return true;
}

/*
 * Try to merge a page into a segment, while obeying the hardware segment
 * size limit.
 *
 * This is kept around for the integrity metadata, which is still tries
 * to build the initial bio to the hardware limit and doesn't have proper
 * helpers to split.  Hopefully this will go away soon.
 */
bool bvec_try_merge_hw_page(struct request_queue *q, struct bio_vec *bv,
		struct page *page, unsigned len, unsigned offset)
{
	unsigned long mask = queue_segment_boundary(q);
	phys_addr_t addr1 = bvec_phys(bv);
	phys_addr_t addr2 = page_to_phys(page) + offset + len - 1;

	if ((addr1 | mask) != (addr2 | mask))
		return false;
	if (len > queue_max_segment_size(q) - bv->bv_len)
		return false;
	return bvec_try_merge_page(bv, page, len, offset);
}

/**
 * __bio_add_page - add page(s) to a bio in a new segment
 * @bio: destination bio
 * @page: start page to add
 * @len: length of the data to add, may cross pages