[thirdparty/kernel/linux.git] / include / 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>

/* 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 int (bio_end_io_t) (struct bio *, unsigned int, 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;
	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 */
	struct bio_set		*bi_set;	/* memory pools set */
};

/*
 * 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

/*
 * 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_cur_sectors(bio)	(bio_iovec(bio)->bv_len >> 9)
#define bio_data(bio)		(page_address(bio_page((bio))) + bio_offset((bio)))
#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))

/*
 * 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, bytes) bio_endio((bio), (bytes), -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, int);
extern void bioset_free(struct bio_set *);

extern struct bio *bio_alloc(unsigned int __nocast, int);
extern struct bio *bio_alloc_bioset(unsigned int __nocast, int, struct bio_set *);
extern void bio_put(struct bio *);

extern void bio_endio(struct bio *, unsigned int, 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 *, unsigned int __nocast);

extern void bio_init(struct bio *);

extern int bio_add_page(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);
extern void bio_unmap_user(struct bio *);
extern void bio_set_pages_dirty(struct bio *bio);
extern void bio_check_pages_dirty(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.
 * Hence the `extern inline'.
 */
extern 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;
}

extern 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

extern 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 /* __LINUX_BIO_H */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* 2.5 block I/O model
	3	*
	4	* Copyright (C) 2001 Jens Axboe <axboe@suse.de>
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License version 2 as
	8	* published by the Free Software Foundation.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public Licens
	17	* along with this program; if not, write to the Free Software
	18	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-
	19	*/
	20	#ifndef __LINUX_BIO_H
	21	#define __LINUX_BIO_H
	22
	23	#include <linux/highmem.h>
	24	#include <linux/mempool.h>
	25
	26	/* Platforms may set this to teach the BIO layer about IOMMU hardware. */
	27	#include <asm/io.h>
	28
	29	#if defined(BIO_VMERGE_MAX_SIZE) && defined(BIO_VMERGE_BOUNDARY)
	30	#define BIOVEC_VIRT_START_SIZE(x) (bvec_to_phys(x) & (BIO_VMERGE_BOUNDARY - 1))
	31	#define BIOVEC_VIRT_OVERSIZE(x) ((x) > BIO_VMERGE_MAX_SIZE)
	32	#else
	33	#define BIOVEC_VIRT_START_SIZE(x) 0
	34	#define BIOVEC_VIRT_OVERSIZE(x) 0
	35	#endif
	36
	37	#ifndef BIO_VMERGE_BOUNDARY
	38	#define BIO_VMERGE_BOUNDARY 0
	39	#endif
	40
	41	#define BIO_DEBUG
	42
	43	#ifdef BIO_DEBUG
	44	#define BIO_BUG_ON BUG_ON
	45	#else
	46	#define BIO_BUG_ON
	47	#endif
	48
	49	#define BIO_MAX_PAGES (256)
	50	#define BIO_MAX_SIZE (BIO_MAX_PAGES << PAGE_CACHE_SHIFT)
	51	#define BIO_MAX_SECTORS (BIO_MAX_SIZE >> 9)
	52
	53	/*
	54	* was unsigned short, but we might as well be ready for > 64kB I/O pages
	55	*/
	56	struct bio_vec {
	57	struct page *bv_page;
	58	unsigned int bv_len;
	59	unsigned int bv_offset;
	60	};
	61
	62	struct bio_set;
	63	struct bio;
	64	typedef int (bio_end_io_t) (struct bio *, unsigned int, int);
65	typedef void (bio_destructor_t) (struct bio *);
66
67	/*
68	* main unit of I/O for the block layer and lower layers (ie drivers and
69	* stacking drivers)
70	*/
71	struct bio {
72	sector_t bi_sector;
73	struct bio bi_next; / request queue link */
74	struct block_device *bi_bdev;
75	unsigned long bi_flags; /* status, command, etc */
76	unsigned long bi_rw; /* bottom bits READ/WRITE,
77	* top bits priority
78	*/
79
80	unsigned short bi_vcnt; /* how many bio_vec's */
81	unsigned short bi_idx; /* current index into bvl_vec */
82
83	/* Number of segments in this BIO after
84	* physical address coalescing is performed.
85	*/
86	unsigned short bi_phys_segments;
87
88	/* Number of segments after physical and DMA remapping
89	* hardware coalescing is performed.
90	*/
91	unsigned short bi_hw_segments;
92
93	unsigned int bi_size; /* residual I/O count */
94
95	/*
96	* To keep track of the max hw size, we account for the
97	* sizes of the first and last virtually mergeable segments
98	* in this bio
99	*/
100	unsigned int bi_hw_front_size;
101	unsigned int bi_hw_back_size;
102
103	unsigned int bi_max_vecs; /* max bvl_vecs we can hold */
104
105	struct bio_vec bi_io_vec; / the actual vec list */
106
107	bio_end_io_t *bi_end_io;
108	atomic_t bi_cnt; /* pin count */
109
110	void *bi_private;
111
112	bio_destructor_t bi_destructor; / destructor */
113	struct bio_set bi_set; / memory pools set */
114	};
115
116	/*
117	* bio flags
118	*/
119	#define BIO_UPTODATE 0 /* ok after I/O completion */
120	#define BIO_RW_BLOCK 1 /* RW_AHEAD set, and read/write would block */
121	#define BIO_EOF 2 /* out-out-bounds error */
122	#define BIO_SEG_VALID 3 /* nr_hw_seg valid */
123	#define BIO_CLONED 4 /* doesn't own data */
124	#define BIO_BOUNCED 5 /* bio is a bounce bio */
125	#define BIO_USER_MAPPED 6 /* contains user pages */
126	#define BIO_EOPNOTSUPP 7 /* not supported */
127	#define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))
128
129	/*
130	* top 4 bits of bio flags indicate the pool this bio came from
131	*/
132	#define BIO_POOL_BITS (4)
133	#define BIO_POOL_OFFSET (BITS_PER_LONG - BIO_POOL_BITS)
134	#define BIO_POOL_MASK (1UL << BIO_POOL_OFFSET)
135	#define BIO_POOL_IDX(bio) ((bio)->bi_flags >> BIO_POOL_OFFSET)
136
137	/*
138	* bio bi_rw flags
139	*
140	* bit 0 -- read (not set) or write (set)
141	* bit 1 -- rw-ahead when set
142	* bit 2 -- barrier
143	* bit 3 -- fail fast, don't want low level driver retries
144	* bit 4 -- synchronous I/O hint: the block layer will unplug immediately
145	*/
146	#define BIO_RW 0
147	#define BIO_RW_AHEAD 1
148	#define BIO_RW_BARRIER 2
149	#define BIO_RW_FAILFAST 3
150	#define BIO_RW_SYNC 4
151
152	/*
153	* various member access, note that bio_data should of course not be used
154	* on highmem page vectors
155	*/
156	#define bio_iovec_idx(bio, idx) (&((bio)->bi_io_vec[(idx)]))
157	#define bio_iovec(bio) bio_iovec_idx((bio), (bio)->bi_idx)
158	#define bio_page(bio) bio_iovec((bio))->bv_page
159	#define bio_offset(bio) bio_iovec((bio))->bv_offset
160	#define bio_segments(bio) ((bio)->bi_vcnt - (bio)->bi_idx)
161	#define bio_sectors(bio) ((bio)->bi_size >> 9)
162	#define bio_cur_sectors(bio) (bio_iovec(bio)->bv_len >> 9)
163	#define bio_data(bio) (page_address(bio_page((bio))) + bio_offset((bio)))
164	#define bio_barrier(bio) ((bio)->bi_rw & (1 << BIO_RW_BARRIER))
165	#define bio_sync(bio) ((bio)->bi_rw & (1 << BIO_RW_SYNC))
166	#define bio_failfast(bio) ((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
167	#define bio_rw_ahead(bio) ((bio)->bi_rw & (1 << BIO_RW_AHEAD))
168
169	/*
170	* will die
171	*/
172	#define bio_to_phys(bio) (page_to_phys(bio_page((bio))) + (unsigned long) bio_offset((bio)))
173	#define bvec_to_phys(bv) (page_to_phys((bv)->bv_page) + (unsigned long) (bv)->bv_offset)
174
175	/*
176	* queues that have highmem support enabled may still need to revert to
177	* PIO transfers occasionally and thus map high pages temporarily. For
178	* permanent PIO fall back, user is probably better off disabling highmem
179	* I/O completely on that queue (see ide-dma for example)
180	*/
181	#define __bio_kmap_atomic(bio, idx, kmtype) \
182	(kmap_atomic(bio_iovec_idx((bio), (idx))->bv_page, kmtype) + \
183	bio_iovec_idx((bio), (idx))->bv_offset)
184
185	#define __bio_kunmap_atomic(addr, kmtype) kunmap_atomic(addr, kmtype)
186
187	/*
188	* merge helpers etc
189	*/
190
191	#define __BVEC_END(bio) bio_iovec_idx((bio), (bio)->bi_vcnt - 1)
192	#define __BVEC_START(bio) bio_iovec_idx((bio), (bio)->bi_idx)
193
194	/*
195	* allow arch override, for eg virtualized architectures (put in asm/io.h)
196	*/
197	#ifndef BIOVEC_PHYS_MERGEABLE
198	#define BIOVEC_PHYS_MERGEABLE(vec1, vec2) \
199	((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))
200	#endif
201
202	#define BIOVEC_VIRT_MERGEABLE(vec1, vec2) \
203	((((bvec_to_phys((vec1)) + (vec1)->bv_len) \| bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0)
204	#define __BIO_SEG_BOUNDARY(addr1, addr2, mask) \
205	(((addr1) \| (mask)) == (((addr2) - 1) \| (mask)))
206	#define BIOVEC_SEG_BOUNDARY(q, b1, b2) \
207	__BIO_SEG_BOUNDARY(bvec_to_phys((b1)), bvec_to_phys((b2)) + (b2)->bv_len, (q)->seg_boundary_mask)
208	#define BIO_SEG_BOUNDARY(q, b1, b2) \
209	BIOVEC_SEG_BOUNDARY((q), __BVEC_END((b1)), __BVEC_START((b2)))
210
211	#define bio_io_error(bio, bytes) bio_endio((bio), (bytes), -EIO)
212
213	/*
214	* drivers should not use the __ version unless they _really_ want to
215	* run through the entire bio and not just pending pieces
216	*/
217	#define __bio_for_each_segment(bvl, bio, i, start_idx) \
218	for (bvl = bio_iovec_idx((bio), (start_idx)), i = (start_idx); \
219	i < (bio)->bi_vcnt; \
220	bvl++, i++)
221
222	#define bio_for_each_segment(bvl, bio, i) \
223	__bio_for_each_segment(bvl, bio, i, (bio)->bi_idx)
224
225	/*
226	* get a reference to a bio, so it won't disappear. the intended use is
227	* something like:
228	*
229	* bio_get(bio);
230	* submit_bio(rw, bio);
231	* if (bio->bi_flags ...)
232	* do_something
233	* bio_put(bio);
234	*
235	* without the bio_get(), it could potentially complete I/O before submit_bio
236	* returns. and then bio would be freed memory when if (bio->bi_flags ...)
237	* runs
238	*/
239	#define bio_get(bio) atomic_inc(&(bio)->bi_cnt)
240
241
242	/*
243	* A bio_pair is used when we need to split a bio.
244	* This can only happen for a bio that refers to just one
245	* page of data, and in the unusual situation when the
246	* page crosses a chunk/device boundary
247	*
248	* The address of the master bio is stored in bio1.bi_private
249	* The address of the pool the pair was allocated from is stored
250	* in bio2.bi_private
251	*/
252	struct bio_pair {
253	struct bio bio1, bio2;
254	struct bio_vec bv1, bv2;
255	atomic_t cnt;
256	int error;
257	};
258	extern struct bio_pair bio_split(struct bio bi, mempool_t *pool,
259	int first_sectors);
260	extern mempool_t *bio_split_pool;
261	extern void bio_pair_release(struct bio_pair *dbio);
262
263	extern struct bio_set *bioset_create(int, int, int);
264	extern void bioset_free(struct bio_set *);
265
266	extern struct bio *bio_alloc(unsigned int __nocast, int);
267	extern struct bio bio_alloc_bioset(unsigned int __nocast, int, struct bio_set );
268	extern void bio_put(struct bio *);
269
270	extern void bio_endio(struct bio *, unsigned int, int);
271	struct request_queue;
272	extern int bio_phys_segments(struct request_queue , struct bio );
273	extern int bio_hw_segments(struct request_queue , struct bio );
274
275	extern void __bio_clone(struct bio , struct bio );
276	extern struct bio bio_clone(struct bio , unsigned int __nocast);
277
278	extern void bio_init(struct bio *);
279
280	extern int bio_add_page(struct bio , struct page , unsigned int,unsigned int);
281	extern int bio_get_nr_vecs(struct block_device *);
282	extern struct bio bio_map_user(struct request_queue , struct block_device *,
283	unsigned long, unsigned int, int);
284	extern void bio_unmap_user(struct bio *);
285	extern void bio_set_pages_dirty(struct bio *bio);
286	extern void bio_check_pages_dirty(struct bio *bio);
287	extern struct bio bio_copy_user(struct request_queue , unsigned long, unsigned int, int);
288	extern int bio_uncopy_user(struct bio *);
289	void zero_fill_bio(struct bio *bio);
290
291	#ifdef CONFIG_HIGHMEM
292	/*
293	* remember to add offset! and never ever reenable interrupts between a
294	* bvec_kmap_irq and bvec_kunmap_irq!!
295	*
296	* This function MUST be inlined - it plays with the CPU interrupt flags.
297	* Hence the `extern inline'.
298	*/
299	extern inline char bvec_kmap_irq(struct bio_vec bvec, unsigned long *flags)
300	{
301	unsigned long addr;
302
303	/*
304	* might not be a highmem page, but the preempt/irq count
305	* balancing is a lot nicer this way
306	*/
307	local_irq_save(*flags);
308	addr = (unsigned long) kmap_atomic(bvec->bv_page, KM_BIO_SRC_IRQ);
309
310	BUG_ON(addr & ~PAGE_MASK);
311
312	return (char *) addr + bvec->bv_offset;
313	}
314
315	extern inline void bvec_kunmap_irq(char buffer, unsigned long flags)
316	{
317	unsigned long ptr = (unsigned long) buffer & PAGE_MASK;
318
319	kunmap_atomic((void *) ptr, KM_BIO_SRC_IRQ);
320	local_irq_restore(*flags);
321	}
322
323	#else
324	#define bvec_kmap_irq(bvec, flags) (page_address((bvec)->bv_page) + (bvec)->bv_offset)
325	#define bvec_kunmap_irq(buf, flags) do { *(flags) = 0; } while (0)
326	#endif
327
328	extern inline char __bio_kmap_irq(struct bio bio, unsigned short idx,
329	unsigned long *flags)
330	{
331	return bvec_kmap_irq(bio_iovec_idx(bio, idx), flags);
332	}
333	#define __bio_kunmap_irq(buf, flags) bvec_kunmap_irq(buf, flags)
334
335	#define bio_kmap_irq(bio, flags) \
336	__bio_kmap_irq((bio), (bio)->bi_idx, (flags))
337	#define bio_kunmap_irq(buf,flags) __bio_kunmap_irq(buf, flags)
338
339	#endif /* __LINUX_BIO_H */