include/linux/bio.h

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