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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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.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/sched/sysctl.h>
 #include <linux/blk-crypto.h>
 #include <linux/xarray.h>
 
 #include <trace/events/block.h>
 #include "blk.h"
 #include "blk-rq-qos.h"
 #include "blk-cgroup.h"
 
 struct bio_alloc_cache {
     struct bio      *free_list;
     unsigned int        nr;
 };
 
 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[8];
 };
 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(sizeof(*bslab), GFP_KERNEL);
 
     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 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);
 }
 
 void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned short nr_vecs)
 {
     BUG_ON(nr_vecs > BIO_MAX_VECS);
 
     if (nr_vecs == BIO_MAX_VECS)
         mempool_free(bv, pool);
     else if (nr_vecs > BIO_INLINE_VECS)
         kmem_cache_free(biovec_slab(nr_vecs)->slab, bv);
 }
 
 /*
  * 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 bvec_alloc_gfp(gfp_t gfp)
 {
     return (gfp & ~(__GFP_DIRECT_RECLAIM | __GFP_IO)) |
         __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
 }
 
 struct bio_vec *bvec_alloc(mempool_t *pool, unsigned short *nr_vecs,
         gfp_t gfp_mask)
 {
     struct biovec_slab *bvs = biovec_slab(*nr_vecs);
 
     if (WARN_ON_ONCE(!bvs))
         return NULL;
 
     /*
      * Upgrade the nr_vecs request to take full advantage of the allocation.
      * We also rely on this in the bvec_free path.
      */
     *nr_vecs = bvs->nr_vecs;
 
     /*
      * Try a slab allocation first for all smaller allocations.  If that
      * fails and __GFP_DIRECT_RECLAIM is set retry with the mempool.
      * The mempool is sized to handle up to BIO_MAX_VECS entries.
      */
     if (*nr_vecs < BIO_MAX_VECS) {
         struct bio_vec *bvl;
 
         bvl = kmem_cache_alloc(bvs->slab, bvec_alloc_gfp(gfp_mask));
         if (likely(bvl) || !(gfp_mask & __GFP_DIRECT_RECLAIM))
             return bvl;
         *nr_vecs = BIO_MAX_VECS;
     }
 
     return mempool_alloc(pool, gfp_mask);
 }
 
 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);
 
     bio_uninit(bio);
     bvec_free(&bs->bvec_pool, bio->bi_io_vec, bio->bi_max_vecs);
     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_status = 0;
     bio->bi_iter.bi_sector = 0;
     bio->bi_iter.bi_size = 0;
     bio->bi_iter.bi_idx = 0;
     bio->bi_iter.bi_bvec_done = 0;
     bio->bi_end_io = NULL;
     bio->bi_private = NULL;
 #ifdef CONFIG_BLK_CGROUP
     bio->bi_blkg = NULL;
     bio->bi_issue.value = 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)
 {
     bio_uninit(bio);
     memset(bio, 0, BIO_RESET_BYTES);
     atomic_set(&bio->__bi_remaining, 1);
     bio->bi_bdev = bdev;
     if (bio->bi_bdev)
         bio_associate_blkg(bio);
     bio->bi_opf = opf;
 }
 EXPORT_SYMBOL(bio_reset);
 
 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;
 }
 
 static void bio_chain_endio(struct bio *bio)
 {
     bio_endio(__bio_chain_endio(bio));
 }
 
 /**
  * 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);
 
 struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
         unsigned int nr_pages, blk_opf_t opf, gfp_t gfp)
 {
     struct bio *new = bio_alloc(bdev, nr_pages, opf, gfp);
 
     if (bio) {
         bio_chain(bio, new);
         submit_bio(bio);
     }
 
     return new;
 }
 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);
     }
 }
 
 static void punt_bios_to_rescuer(struct bio_set *bs)
 {
     struct bio_list punt, nopunt;
     struct bio *bio;
 
     if (WARN_ON_ONCE(!bs->rescue_workqueue))
         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 struct bio *bio_alloc_percpu_cache(struct block_device *bdev,
         unsigned short nr_vecs, blk_opf_t opf, gfp_t gfp,
         struct bio_set *bs)
 {
     struct bio_alloc_cache *cache;
     struct bio *bio;
 
     cache = per_cpu_ptr(bs->cache, get_cpu());
     if (!cache->free_list) {
         put_cpu();
         return NULL;
     }
     bio = cache->free_list;
     cache->free_list = bio->bi_next;
     cache->nr--;
     put_cpu();
 
     bio_init(bio, bdev, nr_vecs ? bio->bi_inline_vecs : NULL, nr_vecs, opf);
     bio->bi_pool = bs;
     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_mask:   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.
  *
  * If REQ_ALLOC_CACHE is set, the final put of the bio MUST be done from process
  * context, not hard/soft IRQ.
  *
  * 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_mask,
                  struct bio_set *bs)
 {
     gfp_t saved_gfp = gfp_mask;
     struct bio *bio;
     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 (opf & REQ_ALLOC_CACHE) {
         if (bs->cache && nr_vecs <= BIO_INLINE_VECS) {
             bio = bio_alloc_percpu_cache(bdev, nr_vecs, opf,
                              gfp_mask, bs);
             if (bio)
                 return bio;
             /*
              * No cached bio available, bio returned below marked with
              * REQ_ALLOC_CACHE to particpate in per-cpu alloc cache.
              */
         } else {
             opf &= ~REQ_ALLOC_CACHE;
         }
     }
 
     /*
      * 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, 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_DIRECT_RECLAIM; 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[0]) ||
          !bio_list_empty(&current->bio_list[1])) &&
         bs->rescue_workqueue)
         gfp_mask &= ~__GFP_DIRECT_RECLAIM;
 
     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);
     }
     if (unlikely(!p))
         return NULL;
 
     bio = p + bs->front_pad;
     if (nr_vecs > BIO_INLINE_VECS) {
         struct bio_vec *bvl = NULL;
 
         bvl = bvec_alloc(&bs->bvec_pool, &nr_vecs, gfp_mask);
         if (!bvl && gfp_mask != saved_gfp) {
             punt_bios_to_rescuer(bs);
             gfp_mask = saved_gfp;
             bvl = bvec_alloc(&bs->bvec_pool, &nr_vecs, gfp_mask);
         }
         if (unlikely(!bvl))
             goto err_free;
 
         bio_init(bio, bdev, bvl, nr_vecs, opf);
     } else if (nr_vecs) {
         bio_init(bio, bdev, bio->bi_inline_vecs, BIO_INLINE_VECS, opf);
     } else {
         bio_init(bio, bdev, NULL, 0, opf);
     }
 
     bio->bi_pool = bs;
     return bio;
 
 err_free:
     mempool_free(p, &bs->bio_pool);
     return NULL;
 }
 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 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 > UIO_MAXIOV)
         return NULL;
     return kmalloc(struct_size(bio, bi_inline_vecs, nr_vecs), 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) {
             unsigned offset;
 
             if (!truncated)
                 offset = new_size - done;
             else
                 offset = 0;
             zero_user(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);
 }
 
 #define ALLOC_CACHE_MAX     512
 #define ALLOC_CACHE_SLACK    64
 
 static void 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--;
         bio_free(bio);
         if (++i == nr)
             break;
     }
 }
 
 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;
 }
 
 /**
  * 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) {
         struct bio_alloc_cache *cache;
 
         bio_uninit(bio);
         cache = per_cpu_ptr(bio->bi_pool->cache, get_cpu());
         bio->bi_next = cache->free_list;
         cache->free_list = bio;
         if (++cache->nr > ALLOC_CACHE_MAX + ALLOC_CACHE_SLACK)
             bio_alloc_cache_prune(cache, ALLOC_CACHE_SLACK);
         put_cpu();
     } 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);
     if (bio_flagged(bio_src, BIO_THROTTLED))
         bio_set_flag(bio, BIO_THROTTLED);
     bio->bi_ioprio = bio_src->bi_ioprio;
     bio->bi_iter = bio_src->bi_iter;
 
     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. The caller owns the returned
  * bio, but not the actual data it points to.
  *
  * The caller must ensure that the return bio is not freed before @bio_src.
  */
 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;
     }
     bio->bi_io_vec = bio_src->bi_io_vec;
 
     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 caller owns the returned bio, but not the actual data it points to.
  *
  * The caller must ensure that @bio_src is not freed before @bio.
  */
 int bio_init_clone(struct block_device *bdev, struct bio *bio,
         struct bio *bio_src, gfp_t gfp)
 {
     int ret;
 
     bio_init(bio, bdev, bio_src->bi_io_vec, 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 > UINT_MAX - len)
         return true;
     return false;
 }
 
 static inline bool page_is_mergeable(const struct bio_vec *bv,
         struct page *page, unsigned int len, unsigned int off,
         bool *same_page)
 {
     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;
 
     *same_page = ((vec_end_addr & PAGE_MASK) == page_addr);
     if (*same_page)
         return true;
     return (bv->bv_page + bv_end / PAGE_SIZE) == (page + off / PAGE_SIZE);
 }
 
 /**
  * __bio_try_merge_page - try appending data to an existing bvec.
  * @bio: destination bio
  * @page: start page to add
  * @len: length of the data to add
  * @off: offset of the data relative to @page
  * @same_page: return if the segment has been merged inside the same page
  *
  * Try to add the data at @page + @off to the last bvec of @bio.  This is a
  * useful optimisation for file systems with a block size smaller than the
  * page size.
  *
  * Warn if (@len, @off) crosses pages in case that @same_page is true.
  *
  * Return %true on success or %false on failure.
  */
 static bool __bio_try_merge_page(struct bio *bio, struct page *page,
         unsigned int len, unsigned int off, bool *same_page)
 {
     if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
         return false;
 
     if (bio->bi_vcnt > 0) {
         struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
         if (page_is_mergeable(bv, page, len, off, same_page)) {
             if (bio->bi_iter.bi_size > UINT_MAX - len) {
                 *same_page = false;
                 return false;
             }
             bv->bv_len += len;
             bio->bi_iter.bi_size += len;
             return true;
         }
     }
     return false;
 }
 
 /*
  * Try to merge a page into a segment, while obeying the hardware segment
  * size limit.  This is not for normal read/write bios, but for passthrough
  * or Zone Append operations that we can't split.
  */
 static bool bio_try_merge_hw_seg(struct request_queue *q, struct bio *bio,
                  struct page *page, unsigned len,
                  unsigned offset, bool *same_page)
 {
     struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
     unsigned long mask = queue_segment_boundary(q);
     phys_addr_t addr1 = page_to_phys(bv->bv_page) + bv->bv_offset;
     phys_addr_t addr2 = page_to_phys(page) + offset + len - 1;
 
     if ((addr1 | mask) != (addr2 | mask))
         return false;
     if (bv->bv_len + len > queue_max_segment_size(q))
         return false;
     return __bio_try_merge_page(bio, page, len, offset, same_page);
 }
 
 /**
  * bio_add_hw_page - attempt to add a page to a bio with hw constraints
  * @q: the target queue
  * @bio: destination bio
  * @page: page to add
  * @len: vec entry length
  * @offset: vec entry offset
  * @max_sectors: maximum number of sectors that can be added
  * @same_page: return if the segment has been merged inside the same page
  *
  * Add a page to a bio while respecting the hardware max_sectors, max_segment
  * and gap limitations.
  */
 int bio_add_hw_page(struct request_queue *q, struct bio *bio,
         struct page *page, unsigned int len, unsigned int offset,
         unsigned int max_sectors, bool *same_page)
 {
     struct bio_vec *bvec;
 
     if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
         return 0;
 
     if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)
         return 0;
 
     if (bio->bi_vcnt > 0) {
         if (bio_try_merge_hw_seg(q, bio, page, len, offset, same_page))
             return len;
 
         /*
          * If the queue doesn't support SG gaps and adding this segment
          * would create a gap, disallow it.
          */
         bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
         if (bvec_gap_to_prev(&q->limits, bvec, offset))
             return 0;
     }
 
     if (bio_full(bio, len))
         return 0;
 
     if (bio->bi_vcnt >= queue_max_segments(q))
         return 0;
 
     bvec = &bio->bi_io_vec[bio->bi_vcnt];
     bvec->bv_page = page;
     bvec->bv_len = len;
     bvec->bv_offset = offset;
     bio->bi_vcnt++;
     bio->bi_iter.bi_size += len;
     return len;
 }
 
 /**
  * bio_add_pc_page  - attempt to add page to passthrough 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 passthrough bios.
  */
 int bio_add_pc_page(struct request_queue *q, struct bio *bio,
         struct page *page, unsigned int len, unsigned int offset)
 {
     bool same_page = false;
     return bio_add_hw_page(q, bio, page, len, offset,
             queue_max_hw_sectors(q), &same_page);
 }
 EXPORT_SYMBOL(bio_add_pc_page);
 
 /**
  * bio_add_zone_append_page - attempt to add page to zone-append 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 of a bio that will be submitted
  * for a zone-append request. This can fail for a number of reasons, such as the
  * bio being full or the target block device is not a zoned block device or
  * other limitations of the target block device. 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.
  *
  * Returns: number of bytes added to the bio, or 0 in case of a failure.
  */
 int bio_add_zone_append_page(struct bio *bio, struct page *page,
                  unsigned int len, unsigned int offset)
 {
     struct request_queue *q = bdev_get_queue(bio->bi_bdev);
     bool same_page = false;
 
     if (WARN_ON_ONCE(bio_op(bio) != REQ_OP_ZONE_APPEND))
         return 0;
 
     if (WARN_ON_ONCE(!bdev_is_zoned(bio->bi_bdev)))
         return 0;
 
     return bio_add_hw_page(q, bio, page, len, offset,
                    queue_max_zone_append_sectors(q), &same_page);
 }
 EXPORT_SYMBOL_GPL(bio_add_zone_append_page);
 
 /**
  * __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
  * @off: offset of the data relative to @page, may cross pages
  *
  * Add the data at @page + @off to @bio as a new bvec.  The caller must ensure
  * that @bio has space for another bvec.
  */
 void __bio_add_page(struct bio *bio, struct page *page,
         unsigned int len, unsigned int off)
 {
     struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt];
 
     WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
     WARN_ON_ONCE(bio_full(bio, len));
 
     bv->bv_page = page;
     bv->bv_offset = off;
     bv->bv_len = len;
 
     bio->bi_iter.bi_size += len;
     bio->bi_vcnt++;
 
     if (!bio_flagged(bio, BIO_WORKINGSET) && unlikely(PageWorkingset(page)))
         bio_set_flag(bio, BIO_WORKINGSET);
 }
 EXPORT_SYMBOL_GPL(__bio_add_page);
 
 /**
  *  bio_add_page    -   attempt to add page(s) to bio
  *  @bio: destination bio
  *  @page: start page to add
  *  @len: vec entry length, may cross pages
  *  @offset: vec entry offset relative to @page, may cross pages
  *
  *  Attempt to add page(s) to the bio_vec maplist. This will only fail
  *  if either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.
  */
 int bio_add_page(struct bio *bio, struct page *page,
          unsigned int len, unsigned int offset)
 {
     bool same_page = false;
 
     if (!__bio_try_merge_page(bio, page, len, offset, &same_page)) {
         if (bio_full(bio, len))
             return 0;
         __bio_add_page(bio, page, len, offset);
     }
     return len;
 }
 EXPORT_SYMBOL(bio_add_page);
 
 /**
  * bio_add_folio - Attempt to add part of a folio to a bio.
  * @bio: BIO to add to.
  * @folio: Folio to add.
  * @len: How many bytes from the folio to add.
  * @off: First byte in this folio to add.
  *
  * Filesystems that use folios can call this function instead of calling
  * bio_add_page() for each page in the folio.  If @off is bigger than
  * PAGE_SIZE, this function can create a bio_vec that starts in a page
  * after the bv_page.  BIOs do not support folios that are 4GiB or larger.
  *
  * Return: Whether the addition was successful.
  */
 bool bio_add_folio(struct bio *bio, struct folio *folio, size_t len,
            size_t off)
 {
     if (len > UINT_MAX || off > UINT_MAX)
         return false;
     return bio_add_page(bio, &folio->page, len, off) > 0;
 }
 
 void __bio_release_pages(struct bio *bio, bool mark_dirty)
 {
     struct bvec_iter_all iter_all;
     struct bio_vec *bvec;
 
     bio_for_each_segment_all(bvec, bio, iter_all) {
         if (mark_dirty && !PageCompound(bvec->bv_page))
             set_page_dirty_lock(bvec->bv_page);
         put_page(bvec->bv_page);
     }
 }
 EXPORT_SYMBOL_GPL(__bio_release_pages);
 
 void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter)
 {
     size_t size = iov_iter_count(iter);
 
     WARN_ON_ONCE(bio->bi_max_vecs);
 
     if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
         struct request_queue *q = bdev_get_queue(bio->bi_bdev);
         size_t max_sectors = queue_max_zone_append_sectors(q);
 
         size = min(size, max_sectors << SECTOR_SHIFT);
     }
 
     bio->bi_vcnt = iter->nr_segs;
     bio->bi_io_vec = (struct bio_vec *)iter->bvec;
     bio->bi_iter.bi_bvec_done = iter->iov_offset;
     bio->bi_iter.bi_size = size;
     bio_set_flag(bio, BIO_NO_PAGE_REF);
     bio_set_flag(bio, BIO_CLONED);
 }
 
 static int bio_iov_add_page(struct bio *bio, struct page *page,
         unsigned int len, unsigned int offset)
 {
     bool same_page = false;
 
     if (!__bio_try_merge_page(bio, page, len, offset, &same_page)) {
         __bio_add_page(bio, page, len, offset);
         return 0;
     }
 
     if (same_page)
         put_page(page);
     return 0;
 }
 
 static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page,
         unsigned int len, unsigned int offset)
 {
     struct request_queue *q = bdev_get_queue(bio->bi_bdev);
     bool same_page = false;
 
     if (bio_add_hw_page(q, bio, page, len, offset,
             queue_max_zone_append_sectors(q), &same_page) != len)
         return -EINVAL;
     if (same_page)
         put_page(page);
     return 0;
 }
 
 #define PAGE_PTRS_PER_BVEC     (sizeof(struct bio_vec) / sizeof(struct page *))
 
 /**
  * __bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
  * @bio: bio to add pages to
  * @iter: iov iterator describing the region to be mapped
  *
  * Pins pages from *iter and appends them to @bio's bvec array. The
  * pages will have to be released using put_page() when done.
  * For multi-segment *iter, this function only adds pages from the
  * next non-empty segment of the iov iterator.
  */
 static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 {
     unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
     unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
     struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
     struct page **pages = (struct page **)bv;
     ssize_t size, left;
     unsigned len, i = 0;
     size_t offset, trim;
     int ret = 0;
 
     /*
      * Move page array up in the allocated memory for the bio vecs as far as
      * possible so that we can start filling biovecs from the beginning
      * without overwriting the temporary page array.
      */
     BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
     pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
 
     /*
      * Each segment in the iov is required to be a block size multiple.
      * However, we may not be able to get the entire segment if it spans
      * more pages than bi_max_vecs allows, so we have to ALIGN_DOWN the
      * result to ensure the bio's total size is correct. The remainder of
      * the iov data will be picked up in the next bio iteration.
      */
     size = iov_iter_get_pages2(iter, pages, UINT_MAX - bio->bi_iter.bi_size,
                   nr_pages, &offset);
     if (unlikely(size <= 0))
         return size ? size : -EFAULT;
 
     nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
 
     trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
     iov_iter_revert(iter, trim);
 
     size -= trim;
     if (unlikely(!size)) {
         ret = -EFAULT;
         goto out;
     }
 
     for (left = size, i = 0; left > 0; left -= len, i++) {
         struct page *page = pages[i];
 
         len = min_t(size_t, PAGE_SIZE - offset, left);
         if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
             ret = bio_iov_add_zone_append_page(bio, page, len,
                     offset);
             if (ret)
                 break;
         } else
             bio_iov_add_page(bio, page, len, offset);
 
         offset = 0;
     }
 
     iov_iter_revert(iter, left);
 out:
     while (i < nr_pages)
         put_page(pages[i++]);
 
     return ret;
 }
 
 /**
  * bio_iov_iter_get_pages - add user or kernel pages to a bio
  * @bio: bio to add pages to
  * @iter: iov iterator describing the region to be added
  *
  * This takes either an iterator pointing to user memory, or one pointing to
  * kernel pages (BVEC iterator). If we're adding user pages, we pin them and
  * map them into the kernel. On IO completion, the caller should put those
  * pages. For bvec based iterators bio_iov_iter_get_pages() uses the provided
  * bvecs rather than copying them. Hence anyone issuing kiocb based IO needs
  * to ensure the bvecs and pages stay referenced until the submitted I/O is
  * completed by a call to ->ki_complete() or returns with an error other than
  * -EIOCBQUEUED. The caller needs to check if the bio is flagged BIO_NO_PAGE_REF
  * on IO completion. If it isn't, then pages should be released.
  *
  * The function tries, but does not guarantee, to pin as many pages as
  * fit into the bio, or are requested in @iter, whatever is smaller. If
  * MM encounters an error pinning the requested pages, it stops. Error
  * is returned only if 0 pages could be pinned.
  *
  * It's intended for direct IO, so doesn't do PSI tracking, the caller is
  * responsible for setting BIO_WORKINGSET if necessary.
  */
 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 {
     int ret = 0;
 
     if (iov_iter_is_bvec(iter)) {
         bio_iov_bvec_set(bio, iter);
         iov_iter_advance(iter, bio->bi_iter.bi_size);
         return 0;
     }
 
     do {
         ret = __bio_iov_iter_get_pages(bio, iter);
     } while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));
 
     /* don't account direct I/O as memory stall */
     bio_clear_flag(bio, BIO_WORKINGSET);
     return bio->bi_vcnt ? 0 : ret;
 }
 EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages);
 
 static void submit_bio_wait_endio(struct bio *bio)
 {
     complete(bio->bi_private);
 }
 
 /**
  * submit_bio_wait - submit a bio, and wait until it completes
  * @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.
  *
  * WARNING: Unlike to how submit_bio() is usually used, this function does not
  * result in bio reference to be consumed. The caller must drop the reference
  * on his own.
  */
 int submit_bio_wait(struct bio *bio)
 {
     DECLARE_COMPLETION_ONSTACK_MAP(done,
             bio->bi_bdev->bd_disk->lockdep_map);
     unsigned long hang_check;
 
     bio->bi_private = &done;
     bio->bi_end_io = submit_bio_wait_endio;
     bio->bi_opf |= REQ_SYNC;
     submit_bio(bio);
 
     /* Prevent hang_check timer from firing at us during very long I/O */
     hang_check = sysctl_hung_task_timeout_secs;
     if (hang_check)
         while (!wait_for_completion_io_timeout(&done,
                     hang_check * (HZ/2)))
             ;
     else
         wait_for_completion_io(&done);
 
     return blk_status_to_errno(bio->bi_status);
 }
 EXPORT_SYMBOL(submit_bio_wait);
 
 void __bio_advance(struct bio *bio, unsigned bytes)
 {
     if (bio_integrity(bio))
         bio_integrity_advance(bio, bytes);
 
     bio_crypt_advance(bio, bytes);
     bio_advance_iter(bio, &bio->bi_iter, bytes);
 }
 EXPORT_SYMBOL(__bio_advance);
 
 void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
             struct bio *src, struct bvec_iter *src_iter)
 {
     while (src_iter->bi_size && dst_iter->bi_size) {
         struct bio_vec src_bv = bio_iter_iovec(src, *src_iter);
         struct bio_vec dst_bv = bio_iter_iovec(dst, *dst_iter);
         unsigned int bytes = min(src_bv.bv_len, dst_bv.bv_len);
         void *src_buf = bvec_kmap_local(&src_bv);
         void *dst_buf = bvec_kmap_local(&dst_bv);
 
         memcpy(dst_buf, src_buf, bytes);
 
         kunmap_local(dst_buf);
         kunmap_local(src_buf);
 
         bio_advance_iter_single(src, src_iter, bytes);
         bio_advance_iter_single(dst, dst_iter, bytes);
     }
 }
 EXPORT_SYMBOL(bio_copy_data_iter);
 
 /**
  * bio_copy_data - copy contents of data buffers from one bio to another
  * @src: source bio
  * @dst: destination bio
  *
  * 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 = src->bi_iter;
     struct bvec_iter dst_iter = dst->bi_iter;
 
     bio_copy_data_iter(dst, &dst_iter, src, &src_iter);
 }
 EXPORT_SYMBOL(bio_copy_data);
 
 void bio_free_pages(struct bio *bio)
 {
     struct bio_vec *bvec;
     struct bvec_iter_all iter_all;
 
     bio_for_each_segment_all(bvec, bio, iter_all)
         __free_page(bvec->bv_page);
 }
 EXPORT_SYMBOL(bio_free_pages);
 
 /*
  * 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;
     struct bvec_iter_all iter_all;
 
     bio_for_each_segment_all(bvec, bio, iter_all) {
         if (!PageCompound(bvec->bv_page))
             set_page_dirty_lock(bvec->bv_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 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 put_page() 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)
 {
     struct bio *bio, *next;
 
     spin_lock_irq(&bio_dirty_lock);
     next = bio_dirty_list;
     bio_dirty_list = NULL;
     spin_unlock_irq(&bio_dirty_lock);
 
     while ((bio = next) != NULL) {
         next = bio->bi_private;
 
         bio_release_pages(bio, true);
         bio_put(bio);
     }
 }
 
 void bio_check_pages_dirty(struct bio *bio)
 {
     struct bio_vec *bvec;
     unsigned long flags;
     struct bvec_iter_all iter_all;
 
     bio_for_each_segment_all(bvec, bio, iter_all) {
         if (!PageDirty(bvec->bv_page) && !PageCompound(bvec->bv_page))
             goto defer;
     }
 
     bio_release_pages(bio, false);
     bio_put(bio);
     return;
 defer:
     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);
 }
 
 static inline bool bio_remaining_done(struct bio *bio)
 {
     /*
      * If we're not chaining, then ->__bi_remaining is always 1 and
      * we always end io on the first invocation.
      */
     if (!bio_flagged(bio, BIO_CHAIN))
         return true;
 
     BUG_ON(atomic_read(&bio->__bi_remaining) <= 0);
 
     if (atomic_dec_and_test(&bio->__bi_remaining)) {
         bio_clear_flag(bio, BIO_CHAIN);
         return true;
     }
 
     return false;
 }
 
 /**
  * bio_endio - end I/O on a bio
  * @bio:    bio
  *
  * Description:
  *   bio_endio() will end I/O on the whole bio. bio_endio() is the preferred
  *   way to end I/O on a bio. 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.
  *
  *   bio_endio() can be called several times on a bio that has been chained
  *   using bio_chain().  The ->bi_end_io() function will only be called the
  *   last time.
  **/
 void bio_endio(struct bio *bio)
 {
 again:
     if (!bio_remaining_done(bio))
         return;
     if (!bio_integrity_endio(bio))
         return;
 
     rq_qos_done_bio(bio);
 
     if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
         trace_block_bio_complete(bdev_get_queue(bio->bi_bdev), bio);
         bio_clear_flag(bio, BIO_TRACE_COMPLETION);
     }
 
     /*
      * 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) {
         bio = __bio_chain_endio(bio);
         goto again;
     }
 
     blk_throtl_bio_endio(bio);
     /* release cgroup info */
     bio_uninit(bio);
     if (bio->bi_end_io)
         bio->bi_end_io(bio);
 }
 EXPORT_SYMBOL(bio_endio);
 
 /**
  * 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.
  *
  * Unless this is a discard request the newly allocated bio will point
  * to @bio's bi_io_vec. It is the caller's responsibility to ensure that
  * neither @bio nor @bs are freed before the split bio.
  */
 struct bio *bio_split(struct bio *bio, int sectors,
               gfp_t gfp, struct bio_set *bs)
 {
     struct bio *split;
 
     BUG_ON(sectors <= 0);
     BUG_ON(sectors >= bio_sectors(bio));
 
     /* Zone append commands cannot be split */
     if (WARN_ON_ONCE(bio_op(bio) == REQ_OP_ZONE_APPEND))
         return NULL;
 
     split = bio_alloc_clone(bio->bi_bdev, bio, gfp, bs);
     if (!split)
         return NULL;
 
     split->bi_iter.bi_size = sectors << 9;
 
     if (bio_integrity(split))
         bio_integrity_trim(split);
 
     bio_advance(bio, split->bi_iter.bi_size);
 
     if (bio_flagged(bio, BIO_TRACE_COMPLETION))
         bio_set_flag(split, BIO_TRACE_COMPLETION);
 
     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
  *
  * This function is typically used for bios that are cloned and submitted
  * to the underlying device in parts.
  */
 void bio_trim(struct bio *bio, sector_t offset, sector_t size)
 {
     if (WARN_ON_ONCE(offset > BIO_MAX_SECTORS || size > BIO_MAX_SECTORS ||
              offset + size > bio_sectors(bio)))
         return;
 
     size <<= 9;
     if (offset == 0 && size == bio->bi_iter.bi_size)
         return;
 
     bio_advance(bio, offset << 9);
     bio->bi_iter.bi_size = size;
 
     if (bio_integrity(bio))
         bio_integrity_trim(bio);
 }
 EXPORT_SYMBOL_GPL(bio_trim);
 
 /*
  * create memory pools for biovec's in a bio_set.
  * use the global biovec slabs created for general use.
  */
 int biovec_init_pool(mempool_t *pool, int pool_entries)
 {
     struct biovec_slab *bp = bvec_slabs + ARRAY_SIZE(bvec_slabs) - 1;
 
     return mempool_init_slab_pool(pool, pool_entries, bp->slab);
 }
 
 /*
  * bioset_exit - exit a bioset initialized with bioset_init()
  *
  * May be called on a zeroed but uninitialized bioset (i.e. allocated with
  * kzalloc()).
  */
 void bioset_exit(struct bio_set *bs)
 {
     bio_alloc_cache_destroy(bs);
     if (bs->rescue_workqueue)
         destroy_workqueue(bs->rescue_workqueue);
     bs->rescue_workqueue = NULL;
 
     mempool_exit(&bs->bio_pool);
     mempool_exit(&bs->bvec_pool);
 
     bioset_integrity_free(bs);
     if (bs->bio_slab)
         bio_put_slab(bs);
     bs->bio_slab = NULL;
 }
 EXPORT_SYMBOL(bioset_exit);
 
 /**
  * bioset_init - Initialize a bio_set
  * @bs:     pool to initialize
  * @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
  * @flags:  Flags to modify behavior, currently %BIOSET_NEED_BVECS
  *              and %BIOSET_NEED_RESCUER
  *
  * 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.
  *    If %BIOSET_NEED_BVECS is set in @flags, a separate pool will be allocated
  *    for allocating iovecs.  This pool is not needed e.g. for bio_init_clone().
  *    If %BIOSET_NEED_RESCUER is set, a workqueue is created which can be used
  *    to dispatch queued requests when the mempool runs out of space.
  *
  */
 int bioset_init(struct bio_set *bs,
         unsigned int pool_size,
         unsigned int front_pad,
         int flags)
 {
     bs->front_pad = front_pad;
     if (flags & BIOSET_NEED_BVECS)
         bs->back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
     else
         bs->back_pad = 0;
 
     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(bs);
     if (!bs->bio_slab)
         return -ENOMEM;
 
     if (mempool_init_slab_pool(&bs->bio_pool, pool_size, bs->bio_slab))
         goto bad;
 
     if ((flags & BIOSET_NEED_BVECS) &&
         biovec_init_pool(&bs->bvec_pool, pool_size))
         goto bad;
 
     if (flags & BIOSET_NEED_RESCUER) {
         bs->rescue_workqueue = alloc_workqueue("bioset",
                             WQ_MEM_RECLAIM, 0);
         if (!bs->rescue_workqueue)
             goto bad;
     }
     if (flags & BIOSET_PERCPU_CACHE) {
         bs->cache = alloc_percpu(struct bio_alloc_cache);
         if (!bs->cache)
             goto bad;
         cpuhp_state_add_instance_nocalls(CPUHP_BIO_DEAD, &bs->cpuhp_dead);
     }
 
     return 0;
 bad:
     bioset_exit(bs);
     return -ENOMEM;
 }
 EXPORT_SYMBOL(bioset_init);
 
 static int __init init_bio(void)
 {
     int i;
 
     bio_integrity_init();
 
     for (i = 0; i < ARRAY_SIZE(bvec_slabs); i++) {
         struct biovec_slab *bvs = bvec_slabs + i;
 
         bvs->slab = kmem_cache_create(bvs->name,
                 bvs->nr_vecs * sizeof(struct bio_vec), 0,
                 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
     }
 
     cpuhp_setup_state_multi(CPUHP_BIO_DEAD, "block/bio:dead", NULL,
                     bio_cpu_dead);
 
     if (bioset_init(&fs_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS))
         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);

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