include/linux/bio.h - kernel/msm-4.19 - Gitiles

 /*
  * 2.5 block I/O model
  *
  * 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>

 #ifdef CONFIG_BLOCK

 /* Platforms may set this to teach the BIO layer about IOMMU hardware. */
 #include <asm/io.h>

 #if defined(BIO_VMERGE_MAX_SIZE) && defined(BIO_VMERGE_BOUNDARY)
 #define BIOVEC_VIRT_START_SIZE(x) (bvec_to_phys(x) & (BIO_VMERGE_BOUNDARY - 1))
 #define BIOVEC_VIRT_OVERSIZE(x)	((x) > BIO_VMERGE_MAX_SIZE)
 #else
 #define BIOVEC_VIRT_START_SIZE(x)	0
 #define BIOVEC_VIRT_OVERSIZE(x)		0
 #endif

 #ifndef BIO_VMERGE_BOUNDARY
 #define BIO_VMERGE_BOUNDARY	0
 #endif

 #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_MAX_SIZE		(BIO_MAX_PAGES << PAGE_CACHE_SHIFT)
 #define BIO_MAX_SECTORS		(BIO_MAX_SIZE >> 9)

 /*
  * was unsigned short, but we might as well be ready for > 64kB I/O pages
  */
 struct bio_vec {
 	struct page	*bv_page;
 	unsigned int	bv_len;
 	unsigned int	bv_offset;
 };

 struct bio_set;
 struct bio;
 typedef void (bio_end_io_t) (struct bio *, int);
 typedef void (bio_destructor_t) (struct bio *);

 /*
  * main unit of I/O for the block layer and lower layers (ie drivers and
  * stacking drivers)
  */
 struct bio {
 	sector_t		bi_sector;	/* device address in 512 byte
 						   sectors */
 	struct bio		*bi_next;	/* request queue link */
 	struct block_device	*bi_bdev;
 	unsigned long		bi_flags;	/* status, command, etc */
 	unsigned long		bi_rw;		/* bottom bits READ/WRITE,
 						 * top bits priority
 						 */

 	unsigned short		bi_vcnt;	/* how many bio_vec's */
 	unsigned short		bi_idx;		/* current index into bvl_vec */

 	/* Number of segments in this BIO after
 	 * physical address coalescing is performed.
 	 */
 	unsigned short		bi_phys_segments;

 	/* Number of segments after physical and DMA remapping
 	 * hardware coalescing is performed.
 	 */
 	unsigned short		bi_hw_segments;

 	unsigned int		bi_size;	/* residual I/O count */

 	/*
 	 * To keep track of the max hw size, we account for the
 	 * sizes of the first and last virtually mergeable segments
 	 * in this bio
 	 */
 	unsigned int		bi_hw_front_size;
 	unsigned int		bi_hw_back_size;

 	unsigned int		bi_max_vecs;	/* max bvl_vecs we can hold */

 	struct bio_vec		*bi_io_vec;	/* the actual vec list */

 	bio_end_io_t		*bi_end_io;
 	atomic_t		bi_cnt;		/* pin count */

 	void			*bi_private;

 	bio_destructor_t	*bi_destructor;	/* destructor */
 };

 /*
  * bio flags
  */
 #define BIO_UPTODATE	0	/* ok after I/O completion */
 #define BIO_RW_BLOCK	1	/* RW_AHEAD set, and read/write would block */
 #define BIO_EOF		2	/* out-out-bounds error */
 #define BIO_SEG_VALID	3	/* nr_hw_seg valid */
 #define BIO_CLONED	4	/* doesn't own data */
 #define BIO_BOUNCED	5	/* bio is a bounce bio */
 #define BIO_USER_MAPPED 6	/* contains user pages */
 #define BIO_EOPNOTSUPP	7	/* not supported */
 #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))

 /*
  * top 4 bits of bio flags indicate the pool this bio came from
  */
 #define BIO_POOL_BITS		(4)
 #define BIO_POOL_OFFSET		(BITS_PER_LONG - BIO_POOL_BITS)
 #define BIO_POOL_MASK		(1UL << BIO_POOL_OFFSET)
 #define BIO_POOL_IDX(bio)	((bio)->bi_flags >> BIO_POOL_OFFSET)

 /*
  * bio bi_rw flags
  *
  * bit 0 -- read (not set) or write (set)
  * bit 1 -- rw-ahead when set
  * bit 2 -- barrier
  * bit 3 -- fail fast, don't want low level driver retries
  * bit 4 -- synchronous I/O hint: the block layer will unplug immediately
  */
 #define BIO_RW		0
 #define BIO_RW_AHEAD	1
 #define BIO_RW_BARRIER	2
 #define BIO_RW_FAILFAST	3
 #define BIO_RW_SYNC	4
 #define BIO_RW_META	5

 /*
  * upper 16 bits of bi_rw define the io priority of this bio
  */
 #define BIO_PRIO_SHIFT	(8 * sizeof(unsigned long) - IOPRIO_BITS)
 #define bio_prio(bio)	((bio)->bi_rw >> BIO_PRIO_SHIFT)
 #define bio_prio_valid(bio)	ioprio_valid(bio_prio(bio))

 #define bio_set_prio(bio, prio)		do {			\
 	WARN_ON(prio >= (1 << IOPRIO_BITS));			\
 	(bio)->bi_rw &= ((1UL << BIO_PRIO_SHIFT) - 1);		\
 	(bio)->bi_rw |= ((unsigned long) (prio) << BIO_PRIO_SHIFT);	\
 } while (0)

 /*
  * various member access, note that bio_data should of course not be used
  * on highmem page vectors
  */
 #define bio_iovec_idx(bio, idx)	(&((bio)->bi_io_vec[(idx)]))
 #define bio_iovec(bio)		bio_iovec_idx((bio), (bio)->bi_idx)
 #define bio_page(bio)		bio_iovec((bio))->bv_page
 #define bio_offset(bio)		bio_iovec((bio))->bv_offset
 #define bio_segments(bio)	((bio)->bi_vcnt - (bio)->bi_idx)
 #define bio_sectors(bio)	((bio)->bi_size >> 9)
 #define bio_barrier(bio)	((bio)->bi_rw & (1 << BIO_RW_BARRIER))
 #define bio_sync(bio)		((bio)->bi_rw & (1 << BIO_RW_SYNC))
 #define bio_failfast(bio)	((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
 #define bio_rw_ahead(bio)	((bio)->bi_rw & (1 << BIO_RW_AHEAD))
 #define bio_rw_meta(bio)	((bio)->bi_rw & (1 << BIO_RW_META))
 #define bio_empty_barrier(bio)	(bio_barrier(bio) && !(bio)->bi_size)

 static inline unsigned int bio_cur_sectors(struct bio *bio)
 {
 	if (bio->bi_vcnt)
 		return bio_iovec(bio)->bv_len >> 9;

 	return 0;
 }

 static inline void *bio_data(struct bio *bio)
 {
 	if (bio->bi_vcnt)
 		return page_address(bio_page(bio)) + bio_offset(bio);

 	return NULL;
 }

 /*
  * will die
  */
 #define bio_to_phys(bio)	(page_to_phys(bio_page((bio))) + (unsigned long) bio_offset((bio)))
 #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, idx, kmtype)				\
 	(kmap_atomic(bio_iovec_idx((bio), (idx))->bv_page, kmtype) +	\
 		bio_iovec_idx((bio), (idx))->bv_offset)

 #define __bio_kunmap_atomic(addr, kmtype) kunmap_atomic(addr, kmtype)

 /*
  * merge helpers etc
  */

 #define __BVEC_END(bio)		bio_iovec_idx((bio), (bio)->bi_vcnt - 1)
 #define __BVEC_START(bio)	bio_iovec_idx((bio), (bio)->bi_idx)

 /*
  * allow arch override, for eg virtualized architectures (put in asm/io.h)
  */
 #ifndef BIOVEC_PHYS_MERGEABLE
 #define BIOVEC_PHYS_MERGEABLE(vec1, vec2)	\
 	((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))
 #endif

 #define BIOVEC_VIRT_MERGEABLE(vec1, vec2)	\
 	((((bvec_to_phys((vec1)) + (vec1)->bv_len) | bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0)
 #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, (q)->seg_boundary_mask)
 #define BIO_SEG_BOUNDARY(q, b1, b2) \
 	BIOVEC_SEG_BOUNDARY((q), __BVEC_END((b1)), __BVEC_START((b2)))

 #define bio_io_error(bio) bio_endio((bio), -EIO)

 /*
  * drivers should not use the __ version unless they _really_ want to
  * run through the entire bio and not just pending pieces
  */
 #define __bio_for_each_segment(bvl, bio, i, start_idx)			\
 	for (bvl = bio_iovec_idx((bio), (start_idx)), i = (start_idx);	\
 	     i < (bio)->bi_vcnt;					\
 	     bvl++, i++)

 #define bio_for_each_segment(bvl, bio, i)				\
 	__bio_for_each_segment(bvl, bio, i, (bio)->bi_idx)

 /*
  * 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
  */
 #define bio_get(bio)	atomic_inc(&(bio)->bi_cnt)


 /*
  * A bio_pair is used when we need to split a bio.
  * This can only happen for a bio that refers to just one
  * page of data, and in the unusual situation when the
  * page crosses a chunk/device boundary
  *
  * The address of the master bio is stored in bio1.bi_private
  * The address of the pool the pair was allocated from is stored
  *   in bio2.bi_private
  */
 struct bio_pair {
 	struct bio	bio1, bio2;
 	struct bio_vec	bv1, bv2;
 	atomic_t	cnt;
 	int		error;
 };
 extern struct bio_pair *bio_split(struct bio *bi, mempool_t *pool,
 				  int first_sectors);
 extern mempool_t *bio_split_pool;
 extern void bio_pair_release(struct bio_pair *dbio);

 extern struct bio_set *bioset_create(int, int);
 extern void bioset_free(struct bio_set *);

 extern struct bio *bio_alloc(gfp_t, int);
 extern struct bio *bio_alloc_bioset(gfp_t, int, struct bio_set *);
 extern void bio_put(struct bio *);
 extern void bio_free(struct bio *, struct bio_set *);

 extern void bio_endio(struct bio *, int);
 struct request_queue;
 extern int bio_phys_segments(struct request_queue *, struct bio *);
 extern int bio_hw_segments(struct request_queue *, struct bio *);

 extern void __bio_clone(struct bio *, struct bio *);
 extern struct bio *bio_clone(struct bio *, gfp_t);

 extern void bio_init(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);
 extern int bio_get_nr_vecs(struct block_device *);
 extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
 				unsigned long, unsigned int, int);
 struct sg_iovec;
 extern struct bio *bio_map_user_iov(struct request_queue *,
 				    struct block_device *,
 				    struct sg_iovec *, int, int);
 extern void bio_unmap_user(struct bio *);
 extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
 				gfp_t);
 extern void bio_set_pages_dirty(struct bio *bio);
 extern void bio_check_pages_dirty(struct bio *bio);
 extern void bio_release_pages(struct bio *bio);
 extern struct bio *bio_copy_user(struct request_queue *, unsigned long, unsigned int, int);
 extern int bio_uncopy_user(struct bio *);
 void zero_fill_bio(struct bio *bio);

 #ifdef CONFIG_HIGHMEM
 /*
  * remember to add offset! and never ever reenable interrupts between a
  * bvec_kmap_irq and bvec_kunmap_irq!!
  *
  * This function MUST be inlined - it plays with the CPU interrupt flags.
  */
 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, KM_BIO_SRC_IRQ);

 	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, KM_BIO_SRC_IRQ);
 	local_irq_restore(*flags);
 }

 #else
 #define bvec_kmap_irq(bvec, flags)	(page_address((bvec)->bv_page) + (bvec)->bv_offset)
 #define bvec_kunmap_irq(buf, flags)	do { *(flags) = 0; } while (0)
 #endif

 static inline char *__bio_kmap_irq(struct bio *bio, unsigned short idx,
 				   unsigned long *flags)
 {
 	return bvec_kmap_irq(bio_iovec_idx(bio, idx), flags);
 }
 #define __bio_kunmap_irq(buf, flags)	bvec_kunmap_irq(buf, flags)

 #define bio_kmap_irq(bio, flags) \
 	__bio_kmap_irq((bio), (bio)->bi_idx, (flags))
 #define bio_kunmap_irq(buf,flags)	__bio_kunmap_irq(buf, flags)

 #endif /* CONFIG_BLOCK */
 #endif /* __LINUX_BIO_H */
	/*
	* 2.5 block I/O model
	*
	* 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>

	#ifdef CONFIG_BLOCK

	/* Platforms may set this to teach the BIO layer about IOMMU hardware. */
	#include <asm/io.h>

	#if defined(BIO_VMERGE_MAX_SIZE) && defined(BIO_VMERGE_BOUNDARY)
	#define BIOVEC_VIRT_START_SIZE(x) (bvec_to_phys(x) & (BIO_VMERGE_BOUNDARY - 1))
	#define BIOVEC_VIRT_OVERSIZE(x) ((x) > BIO_VMERGE_MAX_SIZE)
	#else
	#define BIOVEC_VIRT_START_SIZE(x) 0
	#define BIOVEC_VIRT_OVERSIZE(x) 0
	#endif

	#ifndef BIO_VMERGE_BOUNDARY
	#define BIO_VMERGE_BOUNDARY 0
	#endif

	#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_MAX_SIZE (BIO_MAX_PAGES << PAGE_CACHE_SHIFT)
	#define BIO_MAX_SECTORS (BIO_MAX_SIZE >> 9)

	/*
	* was unsigned short, but we might as well be ready for > 64kB I/O pages
	*/
	struct bio_vec {
	struct page *bv_page;
	unsigned int bv_len;
	unsigned int bv_offset;
	};

	struct bio_set;
	struct bio;
	typedef void (bio_end_io_t) (struct bio *, int);
	typedef void (bio_destructor_t) (struct bio *);

	/*
	* main unit of I/O for the block layer and lower layers (ie drivers and
	* stacking drivers)
	*/
	struct bio {
	sector_t bi_sector; /* device address in 512 byte
	sectors */
	struct bio bi_next; / request queue link */
	struct block_device *bi_bdev;
	unsigned long bi_flags; /* status, command, etc */
	unsigned long bi_rw; /* bottom bits READ/WRITE,
	* top bits priority
	*/

	unsigned short bi_vcnt; /* how many bio_vec's */
	unsigned short bi_idx; /* current index into bvl_vec */

	/* Number of segments in this BIO after
	* physical address coalescing is performed.
	*/
	unsigned short bi_phys_segments;

	/* Number of segments after physical and DMA remapping
	* hardware coalescing is performed.
	*/
	unsigned short bi_hw_segments;

	unsigned int bi_size; /* residual I/O count */

	/*
	* To keep track of the max hw size, we account for the
	* sizes of the first and last virtually mergeable segments
	* in this bio
	*/
	unsigned int bi_hw_front_size;
	unsigned int bi_hw_back_size;

	unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

	struct bio_vec bi_io_vec; / the actual vec list */

	bio_end_io_t *bi_end_io;
	atomic_t bi_cnt; /* pin count */

	void *bi_private;

	bio_destructor_t bi_destructor; / destructor */
	};

	/*
	* bio flags
	*/
	#define BIO_UPTODATE 0 /* ok after I/O completion */
	#define BIO_RW_BLOCK 1 /* RW_AHEAD set, and read/write would block */
	#define BIO_EOF 2 /* out-out-bounds error */
	#define BIO_SEG_VALID 3 /* nr_hw_seg valid */
	#define BIO_CLONED 4 /* doesn't own data */
	#define BIO_BOUNCED 5 /* bio is a bounce bio */
	#define BIO_USER_MAPPED 6 /* contains user pages */
	#define BIO_EOPNOTSUPP 7 /* not supported */
	#define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))

	/*
	* top 4 bits of bio flags indicate the pool this bio came from
	*/
	#define BIO_POOL_BITS (4)
	#define BIO_POOL_OFFSET (BITS_PER_LONG - BIO_POOL_BITS)
	#define BIO_POOL_MASK (1UL << BIO_POOL_OFFSET)
	#define BIO_POOL_IDX(bio) ((bio)->bi_flags >> BIO_POOL_OFFSET)

	/*
	* bio bi_rw flags
	*
	* bit 0 -- read (not set) or write (set)
	* bit 1 -- rw-ahead when set
	* bit 2 -- barrier
	* bit 3 -- fail fast, don't want low level driver retries
	* bit 4 -- synchronous I/O hint: the block layer will unplug immediately
	*/
	#define BIO_RW 0
	#define BIO_RW_AHEAD 1
	#define BIO_RW_BARRIER 2
	#define BIO_RW_FAILFAST 3
	#define BIO_RW_SYNC 4
	#define BIO_RW_META 5

	/*
	* upper 16 bits of bi_rw define the io priority of this bio
	*/
	#define BIO_PRIO_SHIFT (8 * sizeof(unsigned long) - IOPRIO_BITS)
	#define bio_prio(bio) ((bio)->bi_rw >> BIO_PRIO_SHIFT)
	#define bio_prio_valid(bio) ioprio_valid(bio_prio(bio))

	#define bio_set_prio(bio, prio) do { \
	WARN_ON(prio >= (1 << IOPRIO_BITS)); \
	(bio)->bi_rw &= ((1UL << BIO_PRIO_SHIFT) - 1); \
	(bio)->bi_rw \|= ((unsigned long) (prio) << BIO_PRIO_SHIFT); \
	} while (0)

	/*
	* various member access, note that bio_data should of course not be used
	* on highmem page vectors
	*/
	#define bio_iovec_idx(bio, idx) (&((bio)->bi_io_vec[(idx)]))
	#define bio_iovec(bio) bio_iovec_idx((bio), (bio)->bi_idx)
	#define bio_page(bio) bio_iovec((bio))->bv_page
	#define bio_offset(bio) bio_iovec((bio))->bv_offset
	#define bio_segments(bio) ((bio)->bi_vcnt - (bio)->bi_idx)
	#define bio_sectors(bio) ((bio)->bi_size >> 9)
	#define bio_barrier(bio) ((bio)->bi_rw & (1 << BIO_RW_BARRIER))
	#define bio_sync(bio) ((bio)->bi_rw & (1 << BIO_RW_SYNC))
	#define bio_failfast(bio) ((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
	#define bio_rw_ahead(bio) ((bio)->bi_rw & (1 << BIO_RW_AHEAD))
	#define bio_rw_meta(bio) ((bio)->bi_rw & (1 << BIO_RW_META))
	#define bio_empty_barrier(bio) (bio_barrier(bio) && !(bio)->bi_size)

	static inline unsigned int bio_cur_sectors(struct bio *bio)
	{
	if (bio->bi_vcnt)
	return bio_iovec(bio)->bv_len >> 9;

	return 0;
	}

	static inline void bio_data(struct bio bio)
	{
	if (bio->bi_vcnt)
	return page_address(bio_page(bio)) + bio_offset(bio);

	return NULL;
	}

	/*
	* will die
	*/
	#define bio_to_phys(bio) (page_to_phys(bio_page((bio))) + (unsigned long) bio_offset((bio)))
	#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, idx, kmtype) \
	(kmap_atomic(bio_iovec_idx((bio), (idx))->bv_page, kmtype) + \
	bio_iovec_idx((bio), (idx))->bv_offset)

	#define __bio_kunmap_atomic(addr, kmtype) kunmap_atomic(addr, kmtype)

	/*
	* merge helpers etc
	*/

	#define __BVEC_END(bio) bio_iovec_idx((bio), (bio)->bi_vcnt - 1)
	#define __BVEC_START(bio) bio_iovec_idx((bio), (bio)->bi_idx)

	/*
	* allow arch override, for eg virtualized architectures (put in asm/io.h)
	*/
	#ifndef BIOVEC_PHYS_MERGEABLE
	#define BIOVEC_PHYS_MERGEABLE(vec1, vec2) \
	((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))
	#endif

	#define BIOVEC_VIRT_MERGEABLE(vec1, vec2) \
	((((bvec_to_phys((vec1)) + (vec1)->bv_len) \| bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0)
	#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, (q)->seg_boundary_mask)
	#define BIO_SEG_BOUNDARY(q, b1, b2) \
	BIOVEC_SEG_BOUNDARY((q), __BVEC_END((b1)), __BVEC_START((b2)))

	#define bio_io_error(bio) bio_endio((bio), -EIO)

	/*
	* drivers should not use the __ version unless they _really_ want to
	* run through the entire bio and not just pending pieces
	*/
	#define __bio_for_each_segment(bvl, bio, i, start_idx) \
	for (bvl = bio_iovec_idx((bio), (start_idx)), i = (start_idx); \
	i < (bio)->bi_vcnt; \
	bvl++, i++)

	#define bio_for_each_segment(bvl, bio, i) \
	__bio_for_each_segment(bvl, bio, i, (bio)->bi_idx)

	/*
	* 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
	*/
	#define bio_get(bio) atomic_inc(&(bio)->bi_cnt)


	/*
	* A bio_pair is used when we need to split a bio.
	* This can only happen for a bio that refers to just one
	* page of data, and in the unusual situation when the
	* page crosses a chunk/device boundary
	*
	* The address of the master bio is stored in bio1.bi_private
	* The address of the pool the pair was allocated from is stored
	* in bio2.bi_private
	*/
	struct bio_pair {
	struct bio bio1, bio2;
	struct bio_vec bv1, bv2;
	atomic_t cnt;
	int error;
	};
	extern struct bio_pair bio_split(struct bio bi, mempool_t *pool,
	int first_sectors);
	extern mempool_t *bio_split_pool;
	extern void bio_pair_release(struct bio_pair *dbio);

	extern struct bio_set *bioset_create(int, int);
	extern void bioset_free(struct bio_set *);

	extern struct bio *bio_alloc(gfp_t, int);
	extern struct bio bio_alloc_bioset(gfp_t, int, struct bio_set );
	extern void bio_put(struct bio *);
	extern void bio_free(struct bio , struct bio_set );

	extern void bio_endio(struct bio *, int);
	struct request_queue;
	extern int bio_phys_segments(struct request_queue , struct bio );
	extern int bio_hw_segments(struct request_queue , struct bio );

	extern void __bio_clone(struct bio , struct bio );
	extern struct bio bio_clone(struct bio , gfp_t);

	extern void bio_init(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);
	extern int bio_get_nr_vecs(struct block_device *);
	extern struct bio bio_map_user(struct request_queue , struct block_device *,
	unsigned long, unsigned int, int);
	struct sg_iovec;
	extern struct bio bio_map_user_iov(struct request_queue ,
	struct block_device *,
	struct sg_iovec *, int, int);
	extern void bio_unmap_user(struct bio *);
	extern struct bio bio_map_kern(struct request_queue , void *, unsigned int,
	gfp_t);
	extern void bio_set_pages_dirty(struct bio *bio);
	extern void bio_check_pages_dirty(struct bio *bio);
	extern void bio_release_pages(struct bio *bio);
	extern struct bio bio_copy_user(struct request_queue , unsigned long, unsigned int, int);
	extern int bio_uncopy_user(struct bio *);
	void zero_fill_bio(struct bio *bio);

	#ifdef CONFIG_HIGHMEM
	/*
	* remember to add offset! and never ever reenable interrupts between a
	* bvec_kmap_irq and bvec_kunmap_irq!!
	*
	* This function MUST be inlined - it plays with the CPU interrupt flags.
	*/
	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, KM_BIO_SRC_IRQ);

	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, KM_BIO_SRC_IRQ);
	local_irq_restore(*flags);
	}

	#else
	#define bvec_kmap_irq(bvec, flags) (page_address((bvec)->bv_page) + (bvec)->bv_offset)
	#define bvec_kunmap_irq(buf, flags) do { *(flags) = 0; } while (0)
	#endif

	static inline char __bio_kmap_irq(struct bio bio, unsigned short idx,
	unsigned long *flags)
	{
	return bvec_kmap_irq(bio_iovec_idx(bio, idx), flags);
	}
	#define __bio_kunmap_irq(buf, flags) bvec_kunmap_irq(buf, flags)

	#define bio_kmap_irq(bio, flags) \
	__bio_kmap_irq((bio), (bio)->bi_idx, (flags))
	#define bio_kunmap_irq(buf,flags) __bio_kunmap_irq(buf, flags)

	#endif /* CONFIG_BLOCK */
	#endif /* __LINUX_BIO_H */