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dev.c

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  • bio.h 20.23 KiB
    /*
     * 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
    
    #define BIO_MAX_PAGES		256
    
    #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(int rw, unsigned long sectors,
    			   struct hd_struct *part);
    void generic_end_io_acct(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);
    
    #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 */