/*

   * Copyright (C) 2001 Jens Axboe <axboe@suse.de>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of

   *

   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public Licens
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
   */
  #ifndef __LINUX_BIO_H
  #define __LINUX_BIO_H
  
  #include <linux/highmem.h>
  #include <linux/mempool.h>

  #include <linux/ioprio.h>

  #include <linux/bug.h>

  #ifdef CONFIG_BLOCK

  #include <asm/io.h>

  /* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
  #include <linux/blk_types.h>

  #define BIO_DEBUG
  
  #ifdef BIO_DEBUG
  #define BIO_BUG_ON	BUG_ON
  #else
  #define BIO_BUG_ON
  #endif

  #ifdef CONFIG_THP_SWAP
  #if HPAGE_PMD_NR > 256
  #define BIO_MAX_PAGES		HPAGE_PMD_NR
  #else

  #define BIO_MAX_PAGES		256

  #endif
  #else
  #define BIO_MAX_PAGES		256
  #endif

  #define bio_prio(bio)			(bio)->bi_ioprio
  #define bio_set_prio(bio, prio)		((bio)->bi_ioprio = prio)

  #define bio_iter_iovec(bio, iter)				\
  	bvec_iter_bvec((bio)->bi_io_vec, (iter))
  
  #define bio_iter_page(bio, iter)				\
  	bvec_iter_page((bio)->bi_io_vec, (iter))
  #define bio_iter_len(bio, iter)					\
  	bvec_iter_len((bio)->bi_io_vec, (iter))
  #define bio_iter_offset(bio, iter)				\
  	bvec_iter_offset((bio)->bi_io_vec, (iter))
  
  #define bio_page(bio)		bio_iter_page((bio), (bio)->bi_iter)
  #define bio_offset(bio)		bio_iter_offset((bio), (bio)->bi_iter)
  #define bio_iovec(bio)		bio_iter_iovec((bio), (bio)->bi_iter)

  #define bio_multiple_segments(bio)				\
  	((bio)->bi_iter.bi_size != bio_iovec(bio).bv_len)

  #define bio_sectors(bio)	((bio)->bi_iter.bi_size >> 9)
  #define bio_end_sector(bio)	((bio)->bi_iter.bi_sector + bio_sectors((bio)))

  /*

   * Return the data direction, READ or WRITE.
   */
  #define bio_data_dir(bio) \
  	(op_is_write(bio_op(bio)) ? WRITE : READ)
  
  /*

   * Check whether this bio carries any data or not. A NULL bio is allowed.
   */
  static inline bool bio_has_data(struct bio *bio)
  {
  	if (bio &&
  	    bio->bi_iter.bi_size &&

  	    bio_op(bio) != REQ_OP_DISCARD &&

  	    bio_op(bio) != REQ_OP_SECURE_ERASE &&
  	    bio_op(bio) != REQ_OP_WRITE_ZEROES)

  		return true;
  
  	return false;
  }

  static inline bool bio_no_advance_iter(struct bio *bio)
  {

  	return bio_op(bio) == REQ_OP_DISCARD ||
  	       bio_op(bio) == REQ_OP_SECURE_ERASE ||

  	       bio_op(bio) == REQ_OP_WRITE_SAME ||
  	       bio_op(bio) == REQ_OP_WRITE_ZEROES;

  }

  static inline bool bio_mergeable(struct bio *bio)
  {

  	if (bio->bi_opf & REQ_NOMERGE_FLAGS)

  		return false;
  
  	return true;
  }

  static inline unsigned int bio_cur_bytes(struct bio *bio)

  {

  	if (bio_has_data(bio))

  		return bio_iovec(bio).bv_len;

  	else /* dataless requests such as discard */

  		return bio->bi_iter.bi_size;

  }
  
  static inline void *bio_data(struct bio *bio)
  {

  	if (bio_has_data(bio))

  		return page_address(bio_page(bio)) + bio_offset(bio);
  
  	return NULL;
  }

  
  /*
   * will die
   */

  #define bvec_to_phys(bv)	(page_to_phys((bv)->bv_page) + (unsigned long) (bv)->bv_offset)
  
  /*
   * queues that have highmem support enabled may still need to revert to
   * PIO transfers occasionally and thus map high pages temporarily. For
   * permanent PIO fall back, user is probably better off disabling highmem
   * I/O completely on that queue (see ide-dma for example)
   */

  #define __bio_kmap_atomic(bio, iter)				\
  	(kmap_atomic(bio_iter_iovec((bio), (iter)).bv_page) +	\
  		bio_iter_iovec((bio), (iter)).bv_offset)

  #define __bio_kunmap_atomic(addr)	kunmap_atomic(addr)

  
  /*
   * merge helpers etc
   */

  /* Default implementation of BIOVEC_PHYS_MERGEABLE */
  #define __BIOVEC_PHYS_MERGEABLE(vec1, vec2)	\
  	((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))

  /*
   * allow arch override, for eg virtualized architectures (put in asm/io.h)
   */
  #ifndef BIOVEC_PHYS_MERGEABLE
  #define BIOVEC_PHYS_MERGEABLE(vec1, vec2)	\

  	__BIOVEC_PHYS_MERGEABLE(vec1, vec2)

  #endif

  #define __BIO_SEG_BOUNDARY(addr1, addr2, mask) \
  	(((addr1) | (mask)) == (((addr2) - 1) | (mask)))
  #define BIOVEC_SEG_BOUNDARY(q, b1, b2) \

  	__BIO_SEG_BOUNDARY(bvec_to_phys((b1)), bvec_to_phys((b2)) + (b2)->bv_len, queue_segment_boundary((q)))

  /*

   * drivers should _never_ use the all version - the bio may have been split
   * before it got to the driver and the driver won't own all of it
   */
  #define bio_for_each_segment_all(bvl, bio, i)				\

  	for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++)

  static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
  				    unsigned bytes)
  {
  	iter->bi_sector += bytes >> 9;

  	if (bio_no_advance_iter(bio)) {

  		iter->bi_size -= bytes;

  		iter->bi_done += bytes;
  	} else {

  		bvec_iter_advance(bio->bi_io_vec, iter, bytes);

  		/* TODO: It is reasonable to complete bio with error here. */
  	}

  }

  static inline bool bio_rewind_iter(struct bio *bio, struct bvec_iter *iter,
  		unsigned int bytes)
  {
  	iter->bi_sector -= bytes >> 9;
  
  	if (bio_no_advance_iter(bio)) {
  		iter->bi_size += bytes;
  		iter->bi_done -= bytes;
  		return true;
  	}
  
  	return bvec_iter_rewind(bio->bi_io_vec, iter, bytes);
  }

  #define __bio_for_each_segment(bvl, bio, iter, start)			\
  	for (iter = (start);						\

  	     (iter).bi_size &&						\
  		((bvl = bio_iter_iovec((bio), (iter))), 1);		\
  	     bio_advance_iter((bio), &(iter), (bvl).bv_len))

  
  #define bio_for_each_segment(bvl, bio, iter)				\
  	__bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter)

  #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)

  static inline unsigned bio_segments(struct bio *bio)

  {
  	unsigned segs = 0;
  	struct bio_vec bv;
  	struct bvec_iter iter;

  	/*

  	 * We special case discard/write same/write zeroes, because they
  	 * interpret bi_size differently:

  	 */

  	switch (bio_op(bio)) {
  	case REQ_OP_DISCARD:
  	case REQ_OP_SECURE_ERASE:

  	case REQ_OP_WRITE_ZEROES:

  		return 0;
  	case REQ_OP_WRITE_SAME:

  		return 1;

  	default:
  		break;
  	}

  	bio_for_each_segment(bv, bio, iter)

  		segs++;
  
  	return segs;
  }

  /*
   * get a reference to a bio, so it won't disappear. the intended use is
   * something like:
   *
   * bio_get(bio);
   * submit_bio(rw, bio);
   * if (bio->bi_flags ...)
   *	do_something
   * bio_put(bio);
   *
   * without the bio_get(), it could potentially complete I/O before submit_bio
   * returns. and then bio would be freed memory when if (bio->bi_flags ...)
   * runs
   */

  static inline void bio_get(struct bio *bio)
  {
  	bio->bi_flags |= (1 << BIO_REFFED);
  	smp_mb__before_atomic();
  	atomic_inc(&bio->__bi_cnt);
  }
  
  static inline void bio_cnt_set(struct bio *bio, unsigned int count)
  {
  	if (count != 1) {
  		bio->bi_flags |= (1 << BIO_REFFED);
  		smp_mb__before_atomic();
  	}
  	atomic_set(&bio->__bi_cnt, count);
  }

  static inline bool bio_flagged(struct bio *bio, unsigned int bit)
  {

  	return (bio->bi_flags & (1U << bit)) != 0;

  }
  
  static inline void bio_set_flag(struct bio *bio, unsigned int bit)
  {

  	bio->bi_flags |= (1U << bit);

  }
  
  static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
  {

  	bio->bi_flags &= ~(1U << bit);

  }

  static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
  {
  	*bv = bio_iovec(bio);
  }
  
  static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
  {
  	struct bvec_iter iter = bio->bi_iter;
  	int idx;

  	if (unlikely(!bio_multiple_segments(bio))) {
  		*bv = bio_iovec(bio);
  		return;
  	}
  
  	bio_advance_iter(bio, &iter, iter.bi_size);
  
  	if (!iter.bi_bvec_done)
  		idx = iter.bi_idx - 1;
  	else	/* in the middle of bvec */
  		idx = iter.bi_idx;
  
  	*bv = bio->bi_io_vec[idx];
  
  	/*
  	 * iter.bi_bvec_done records actual length of the last bvec
  	 * if this bio ends in the middle of one io vector
  	 */
  	if (iter.bi_bvec_done)
  		bv->bv_len = iter.bi_bvec_done;
  }

  enum bip_flags {
  	BIP_BLOCK_INTEGRITY	= 1 << 0, /* block layer owns integrity data */
  	BIP_MAPPED_INTEGRITY	= 1 << 1, /* ref tag has been remapped */
  	BIP_CTRL_NOCHECK	= 1 << 2, /* disable HBA integrity checking */
  	BIP_DISK_NOCHECK	= 1 << 3, /* disable disk integrity checking */
  	BIP_IP_CHECKSUM		= 1 << 4, /* IP checksum */
  };

  /*
   * bio integrity payload
   */
  struct bio_integrity_payload {
  	struct bio		*bip_bio;	/* parent bio */

  	struct bvec_iter	bip_iter;

  	unsigned short		bip_slab;	/* slab the bip came from */

  	unsigned short		bip_vcnt;	/* # of integrity bio_vecs */

  	unsigned short		bip_max_vcnt;	/* integrity bio_vec slots */

  	unsigned short		bip_flags;	/* control flags */

  
  	struct work_struct	bip_work;	/* I/O completion */

  
  	struct bio_vec		*bip_vec;
  	struct bio_vec		bip_inline_vecs[0];/* embedded bvec array */

  };

  #if defined(CONFIG_BLK_DEV_INTEGRITY)
  
  static inline struct bio_integrity_payload *bio_integrity(struct bio *bio)
  {

  	if (bio->bi_opf & REQ_INTEGRITY)

  		return bio->bi_integrity;
  
  	return NULL;
  }

  static inline bool bio_integrity_flagged(struct bio *bio, enum bip_flags flag)
  {
  	struct bio_integrity_payload *bip = bio_integrity(bio);
  
  	if (bip)
  		return bip->bip_flags & flag;
  
  	return false;
  }

  static inline sector_t bip_get_seed(struct bio_integrity_payload *bip)
  {
  	return bip->bip_iter.bi_sector;
  }
  
  static inline void bip_set_seed(struct bio_integrity_payload *bip,
  				sector_t seed)
  {
  	bip->bip_iter.bi_sector = seed;
  }

  #endif /* CONFIG_BLK_DEV_INTEGRITY */

  extern void bio_trim(struct bio *bio, int offset, int size);

  extern struct bio *bio_split(struct bio *bio, int sectors,
  			     gfp_t gfp, struct bio_set *bs);
  
  /**
   * bio_next_split - get next @sectors from a bio, splitting if necessary
   * @bio:	bio to split
   * @sectors:	number of sectors to split from the front of @bio
   * @gfp:	gfp mask
   * @bs:		bio set to allocate from
   *
   * Returns a bio representing the next @sectors of @bio - if the bio is smaller
   * than @sectors, returns the original bio unchanged.
   */
  static inline struct bio *bio_next_split(struct bio *bio, int sectors,
  					 gfp_t gfp, struct bio_set *bs)
  {
  	if (sectors >= bio_sectors(bio))
  		return bio;
  
  	return bio_split(bio, sectors, gfp, bs);
  }

  extern struct bio_set *bioset_create(unsigned int, unsigned int, int flags);
  enum {
  	BIOSET_NEED_BVECS = BIT(0),

  	BIOSET_NEED_RESCUER = BIT(1),

  };

  extern void bioset_free(struct bio_set *);

  extern mempool_t *biovec_create_pool(int pool_entries);

  extern struct bio *bio_alloc_bioset(gfp_t, unsigned int, struct bio_set *);

  extern void bio_put(struct bio *);

  extern void __bio_clone_fast(struct bio *, struct bio *);
  extern struct bio *bio_clone_fast(struct bio *, gfp_t, struct bio_set *);

  extern struct bio *bio_clone_bioset(struct bio *, gfp_t, struct bio_set *bs);

  extern struct bio_set *fs_bio_set;
  
  static inline struct bio *bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)
  {
  	return bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
  }
  
  static inline struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs)
  {
  	return bio_alloc_bioset(gfp_mask, nr_iovecs, NULL);
  }

  static inline struct bio *bio_clone_kmalloc(struct bio *bio, gfp_t gfp_mask)
  {
  	return bio_clone_bioset(bio, gfp_mask, NULL);
  
  }

  extern blk_qc_t submit_bio(struct bio *);

  extern void bio_endio(struct bio *);
  
  static inline void bio_io_error(struct bio *bio)
  {

  	bio->bi_status = BLK_STS_IOERR;

  	bio_endio(bio);
  }

  static inline void bio_wouldblock_error(struct bio *bio)
  {
  	bio->bi_status = BLK_STS_AGAIN;

  	bio_endio(bio);
  }

  struct request_queue;
  extern int bio_phys_segments(struct request_queue *, struct bio *);

  extern int submit_bio_wait(struct bio *bio);

  extern void bio_advance(struct bio *, unsigned);

  extern void bio_init(struct bio *bio, struct bio_vec *table,
  		     unsigned short max_vecs);

  extern void bio_uninit(struct bio *);

  extern void bio_reset(struct bio *);

  void bio_chain(struct bio *, struct bio *);

  
  extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);

  extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
  			   unsigned int, unsigned int);

  int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);

  struct rq_map_data;

  extern struct bio *bio_map_user_iov(struct request_queue *,

  				    const struct iov_iter *, gfp_t);

  extern void bio_unmap_user(struct bio *);

  extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,

  				gfp_t);

  extern struct bio *bio_copy_kern(struct request_queue *, void *, unsigned int,
  				 gfp_t, int);

  extern void bio_set_pages_dirty(struct bio *bio);
  extern void bio_check_pages_dirty(struct bio *bio);

  void generic_start_io_acct(struct request_queue *q, int rw,
  				unsigned long sectors, struct hd_struct *part);
  void generic_end_io_acct(struct request_queue *q, int rw,
  				struct hd_struct *part,
  				unsigned long start_time);

  #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
  # error	"You should define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE for your platform"
  #endif
  #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
  extern void bio_flush_dcache_pages(struct bio *bi);
  #else
  static inline void bio_flush_dcache_pages(struct bio *bi)
  {
  }
  #endif

  extern void bio_copy_data(struct bio *dst, struct bio *src);

  extern int bio_alloc_pages(struct bio *bio, gfp_t gfp);

  extern void bio_free_pages(struct bio *bio);

  extern struct bio *bio_copy_user_iov(struct request_queue *,

  				     struct rq_map_data *,

  				     const struct iov_iter *,
  				     gfp_t);

  extern int bio_uncopy_user(struct bio *);
  void zero_fill_bio(struct bio *bio);

  extern struct bio_vec *bvec_alloc(gfp_t, int, unsigned long *, mempool_t *);
  extern void bvec_free(mempool_t *, struct bio_vec *, unsigned int);

  extern unsigned int bvec_nr_vecs(unsigned short idx);

  extern const char *bio_devname(struct bio *bio, char *buffer);

  #define bio_set_dev(bio, bdev) 			\
  do {						\

  	if ((bio)->bi_disk != (bdev)->bd_disk)	\
  		bio_clear_flag(bio, BIO_THROTTLED);\

  	(bio)->bi_disk = (bdev)->bd_disk;	\
  	(bio)->bi_partno = (bdev)->bd_partno;	\
  } while (0)
  
  #define bio_copy_dev(dst, src)			\
  do {						\
  	(dst)->bi_disk = (src)->bi_disk;	\
  	(dst)->bi_partno = (src)->bi_partno;	\
  } while (0)
  
  #define bio_dev(bio) \
  	disk_devt((bio)->bi_disk)

  #ifdef CONFIG_BLK_CGROUP

  int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);

  int bio_associate_current(struct bio *bio);
  void bio_disassociate_task(struct bio *bio);

  void bio_clone_blkcg_association(struct bio *dst, struct bio *src);

  #else	/* CONFIG_BLK_CGROUP */

  static inline int bio_associate_blkcg(struct bio *bio,
  			struct cgroup_subsys_state *blkcg_css) { return 0; }

  static inline int bio_associate_current(struct bio *bio) { return -ENOENT; }
  static inline void bio_disassociate_task(struct bio *bio) { }

  static inline void bio_clone_blkcg_association(struct bio *dst,
  			struct bio *src) { }

  #endif	/* CONFIG_BLK_CGROUP */

  #ifdef CONFIG_HIGHMEM
  /*

   * remember never ever reenable interrupts between a bvec_kmap_irq and
   * bvec_kunmap_irq!

   */

  static inline char *bvec_kmap_irq(struct bio_vec *bvec, unsigned long *flags)

  {
  	unsigned long addr;
  
  	/*
  	 * might not be a highmem page, but the preempt/irq count
  	 * balancing is a lot nicer this way
  	 */
  	local_irq_save(*flags);

  	addr = (unsigned long) kmap_atomic(bvec->bv_page);

  
  	BUG_ON(addr & ~PAGE_MASK);
  
  	return (char *) addr + bvec->bv_offset;
  }

  static inline void bvec_kunmap_irq(char *buffer, unsigned long *flags)

  {
  	unsigned long ptr = (unsigned long) buffer & PAGE_MASK;

  	kunmap_atomic((void *) ptr);

  	local_irq_restore(*flags);
  }
  
  #else

  static inline char *bvec_kmap_irq(struct bio_vec *bvec, unsigned long *flags)
  {
  	return page_address(bvec->bv_page) + bvec->bv_offset;
  }
  
  static inline void bvec_kunmap_irq(char *buffer, unsigned long *flags)
  {
  	*flags = 0;
  }

  #endif

  static inline char *__bio_kmap_irq(struct bio *bio, struct bvec_iter iter,

  				   unsigned long *flags)
  {

  	return bvec_kmap_irq(&bio_iter_iovec(bio, iter), flags);

  }
  #define __bio_kunmap_irq(buf, flags)	bvec_kunmap_irq(buf, flags)
  
  #define bio_kmap_irq(bio, flags) \

  	__bio_kmap_irq((bio), (bio)->bi_iter, (flags))

  #define bio_kunmap_irq(buf,flags)	__bio_kunmap_irq(buf, flags)

  /*

   * BIO list management for use by remapping drivers (e.g. DM or MD) and loop.

   *
   * A bio_list anchors a singly-linked list of bios chained through the bi_next
   * member of the bio.  The bio_list also caches the last list member to allow
   * fast access to the tail.
   */
  struct bio_list {
  	struct bio *head;
  	struct bio *tail;
  };
  
  static inline int bio_list_empty(const struct bio_list *bl)
  {
  	return bl->head == NULL;
  }
  
  static inline void bio_list_init(struct bio_list *bl)
  {
  	bl->head = bl->tail = NULL;
  }

  #define BIO_EMPTY_LIST	{ NULL, NULL }

  #define bio_list_for_each(bio, bl) \
  	for (bio = (bl)->head; bio; bio = bio->bi_next)
  
  static inline unsigned bio_list_size(const struct bio_list *bl)
  {
  	unsigned sz = 0;
  	struct bio *bio;
  
  	bio_list_for_each(bio, bl)
  		sz++;
  
  	return sz;
  }
  
  static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
  {
  	bio->bi_next = NULL;
  
  	if (bl->tail)
  		bl->tail->bi_next = bio;
  	else
  		bl->head = bio;
  
  	bl->tail = bio;
  }
  
  static inline void bio_list_add_head(struct bio_list *bl, struct bio *bio)
  {
  	bio->bi_next = bl->head;
  
  	bl->head = bio;
  
  	if (!bl->tail)
  		bl->tail = bio;
  }
  
  static inline void bio_list_merge(struct bio_list *bl, struct bio_list *bl2)
  {
  	if (!bl2->head)
  		return;
  
  	if (bl->tail)
  		bl->tail->bi_next = bl2->head;
  	else
  		bl->head = bl2->head;
  
  	bl->tail = bl2->tail;
  }
  
  static inline void bio_list_merge_head(struct bio_list *bl,
  				       struct bio_list *bl2)
  {
  	if (!bl2->head)
  		return;
  
  	if (bl->head)
  		bl2->tail->bi_next = bl->head;
  	else
  		bl->tail = bl2->tail;
  
  	bl->head = bl2->head;
  }

  static inline struct bio *bio_list_peek(struct bio_list *bl)
  {
  	return bl->head;
  }

  static inline struct bio *bio_list_pop(struct bio_list *bl)
  {
  	struct bio *bio = bl->head;
  
  	if (bio) {
  		bl->head = bl->head->bi_next;
  		if (!bl->head)
  			bl->tail = NULL;
  
  		bio->bi_next = NULL;
  	}
  
  	return bio;
  }
  
  static inline struct bio *bio_list_get(struct bio_list *bl)
  {
  	struct bio *bio = bl->head;
  
  	bl->head = bl->tail = NULL;
  
  	return bio;
  }

  /*

   * Increment chain count for the bio. Make sure the CHAIN flag update
   * is visible before the raised count.
   */
  static inline void bio_inc_remaining(struct bio *bio)
  {
  	bio_set_flag(bio, BIO_CHAIN);
  	smp_mb__before_atomic();
  	atomic_inc(&bio->__bi_remaining);
  }
  
  /*

   * bio_set is used to allow other portions of the IO system to
   * allocate their own private memory pools for bio and iovec structures.
   * These memory pools in turn all allocate from the bio_slab
   * and the bvec_slabs[].
   */
  #define BIO_POOL_SIZE 2

  
  struct bio_set {
  	struct kmem_cache *bio_slab;
  	unsigned int front_pad;
  
  	mempool_t *bio_pool;

  	mempool_t *bvec_pool;

  #if defined(CONFIG_BLK_DEV_INTEGRITY)
  	mempool_t *bio_integrity_pool;

  	mempool_t *bvec_integrity_pool;

  #endif

  
  	/*
  	 * Deadlock avoidance for stacking block drivers: see comments in
  	 * bio_alloc_bioset() for details
  	 */
  	spinlock_t		rescue_lock;
  	struct bio_list		rescue_list;
  	struct work_struct	rescue_work;
  	struct workqueue_struct	*rescue_workqueue;

  };
  
  struct biovec_slab {
  	int nr_vecs;
  	char *name;
  	struct kmem_cache *slab;
  };
  
  /*
   * a small number of entries is fine, not going to be performance critical.
   * basically we just need to survive
   */
  #define BIO_SPLIT_ENTRIES 2

  #if defined(CONFIG_BLK_DEV_INTEGRITY)

  #define bip_for_each_vec(bvl, bip, iter)				\
  	for_each_bvec(bvl, (bip)->bip_vec, iter, (bip)->bip_iter)

  #define bio_for_each_integrity_vec(_bvl, _bio, _iter)			\
  	for_each_bio(_bio)						\
  		bip_for_each_vec(_bvl, _bio->bi_integrity, _iter)

  extern struct bio_integrity_payload *bio_integrity_alloc(struct bio *, gfp_t, unsigned int);

  extern int bio_integrity_add_page(struct bio *, struct page *, unsigned int, unsigned int);

  extern bool bio_integrity_prep(struct bio *);

  extern void bio_integrity_advance(struct bio *, unsigned int);

  extern void bio_integrity_trim(struct bio *);

  extern int bio_integrity_clone(struct bio *, struct bio *, gfp_t);

  extern int bioset_integrity_create(struct bio_set *, int);
  extern void bioset_integrity_free(struct bio_set *);
  extern void bio_integrity_init(void);

  
  #else /* CONFIG_BLK_DEV_INTEGRITY */

  static inline void *bio_integrity(struct bio *bio)

  {

  	return NULL;

  }

  static inline int bioset_integrity_create(struct bio_set *bs, int pool_size)
  {
  	return 0;
  }
  
  static inline void bioset_integrity_free (struct bio_set *bs)
  {
  	return;
  }

  static inline bool bio_integrity_prep(struct bio *bio)

  {

  	return true;

  }

  static inline int bio_integrity_clone(struct bio *bio, struct bio *bio_src,

  				      gfp_t gfp_mask)

  {
  	return 0;
  }

  static inline void bio_integrity_advance(struct bio *bio,
  					 unsigned int bytes_done)
  {
  	return;
  }

  static inline void bio_integrity_trim(struct bio *bio)

  {
  	return;
  }
  
  static inline void bio_integrity_init(void)
  {
  	return;
  }

  static inline bool bio_integrity_flagged(struct bio *bio, enum bip_flags flag)
  {
  	return false;
  }

  static inline void *bio_integrity_alloc(struct bio * bio, gfp_t gfp,
  								unsigned int nr)
  {
  	return ERR_PTR(-EINVAL);
  }
  
  static inline int bio_integrity_add_page(struct bio *bio, struct page *page,
  					unsigned int len, unsigned int offset)
  {
  	return 0;
  }

  #endif /* CONFIG_BLK_DEV_INTEGRITY */

  #endif /* CONFIG_BLOCK */

  #endif /* __LINUX_BIO_H */