LXR linux-bk/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 */
  56struct bio_vec {
  57        struct page     *bv_page;
  58        unsigned int    bv_len;
  59        unsigned int    bv_offset;
  60};
  61
  62struct bio;
  63typedef int (bio_end_io_t) (struct bio *, unsigned int, int);
  64typedef 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 */
  70struct 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_flagged(bio, flag)  ((bio)->bi_flags & (1 << (flag)))
 125
 126/*
 127 * top 4 bits of bio flags indicate the pool this bio came from
 128 */
 129#define BIO_POOL_BITS           (4)
 130#define BIO_POOL_OFFSET         (BITS_PER_LONG - BIO_POOL_BITS)
 131#define BIO_POOL_MASK           (1UL << BIO_POOL_OFFSET)
 132#define BIO_POOL_IDX(bio)       ((bio)->bi_flags >> BIO_POOL_OFFSET)    
 133
 134/*
 135 * bio bi_rw flags
 136 *
 137 * bit 0 -- read (not set) or write (set)
 138 * bit 1 -- rw-ahead when set
 139 * bit 2 -- barrier
 140 * bit 3 -- fail fast, don't want low level driver retries
 141 * bit 4 -- synchronous I/O hint: the block layer will unplug immediately
 142 */
 143#define BIO_RW          0
 144#define BIO_RW_AHEAD    1
 145#define BIO_RW_BARRIER  2
 146#define BIO_RW_FAILFAST 3
 147#define BIO_RW_SYNC     4
 148
 149/*
 150 * various member access, note that bio_data should of course not be used
 151 * on highmem page vectors
 152 */
 153#define bio_iovec_idx(bio, idx) (&((bio)->bi_io_vec[(idx)]))
 154#define bio_iovec(bio)          bio_iovec_idx((bio), (bio)->bi_idx)
 155#define bio_page(bio)           bio_iovec((bio))->bv_page
 156#define bio_offset(bio)         bio_iovec((bio))->bv_offset
 157#define bio_segments(bio)       ((bio)->bi_vcnt - (bio)->bi_idx)
 158#define bio_sectors(bio)        ((bio)->bi_size >> 9)
 159#define bio_cur_sectors(bio)    (bio_iovec(bio)->bv_len >> 9)
 160#define bio_data(bio)           (page_address(bio_page((bio))) + bio_offset((bio)))
 161#define bio_barrier(bio)        ((bio)->bi_rw & (1 << BIO_RW_BARRIER))
 162#define bio_sync(bio)           ((bio)->bi_rw & (1 << BIO_RW_SYNC))
 163
 164/*
 165 * will die
 166 */
 167#define bio_to_phys(bio)        (page_to_phys(bio_page((bio))) + (unsigned long) bio_offset((bio)))
 168#define bvec_to_phys(bv)        (page_to_phys((bv)->bv_page) + (unsigned long) (bv)->bv_offset)
 169
 170/*
 171 * queues that have highmem support enabled may still need to revert to
 172 * PIO transfers occasionally and thus map high pages temporarily. For
 173 * permanent PIO fall back, user is probably better off disabling highmem
 174 * I/O completely on that queue (see ide-dma for example)
 175 */
 176#define __bio_kmap_atomic(bio, idx, kmtype)                             \
 177        (kmap_atomic(bio_iovec_idx((bio), (idx))->bv_page, kmtype) +    \
 178                bio_iovec_idx((bio), (idx))->bv_offset)
 179
 180#define __bio_kunmap_atomic(addr, kmtype) kunmap_atomic(addr, kmtype)
 181
 182/*
 183 * merge helpers etc
 184 */
 185
 186#define __BVEC_END(bio)         bio_iovec_idx((bio), (bio)->bi_vcnt - 1)
 187#define __BVEC_START(bio)       bio_iovec_idx((bio), (bio)->bi_idx)
 188#define BIOVEC_PHYS_MERGEABLE(vec1, vec2)       \
 189        ((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))
 190#define BIOVEC_VIRT_MERGEABLE(vec1, vec2)       \
 191        ((((bvec_to_phys((vec1)) + (vec1)->bv_len) | bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0)
 192#define __BIO_SEG_BOUNDARY(addr1, addr2, mask) \
 193        (((addr1) | (mask)) == (((addr2) - 1) | (mask)))
 194#define BIOVEC_SEG_BOUNDARY(q, b1, b2) \
 195        __BIO_SEG_BOUNDARY(bvec_to_phys((b1)), bvec_to_phys((b2)) + (b2)->bv_len, (q)->seg_boundary_mask)
 196#define BIO_SEG_BOUNDARY(q, b1, b2) \
 197        BIOVEC_SEG_BOUNDARY((q), __BVEC_END((b1)), __BVEC_START((b2)))
 198
 199#define bio_io_error(bio, bytes) bio_endio((bio), (bytes), -EIO)
 200
 201/*
 202 * drivers should not use the __ version unless they _really_ want to
 203 * run through the entire bio and not just pending pieces
 204 */
 205#define __bio_for_each_segment(bvl, bio, i, start_idx)                  \
 206        for (bvl = bio_iovec_idx((bio), (start_idx)), i = (start_idx);  \
 207             i < (bio)->bi_vcnt;                                        \
 208             bvl++, i++)
 209
 210#define bio_for_each_segment(bvl, bio, i)                               \
 211        __bio_for_each_segment(bvl, bio, i, (bio)->bi_idx)
 212
 213/*
 214 * get a reference to a bio, so it won't disappear. the intended use is
 215 * something like:
 216 *
 217 * bio_get(bio);
 218 * submit_bio(rw, bio);
 219 * if (bio->bi_flags ...)
 220 *      do_something
 221 * bio_put(bio);
 222 *
 223 * without the bio_get(), it could potentially complete I/O before submit_bio
 224 * returns. and then bio would be freed memory when if (bio->bi_flags ...)
 225 * runs
 226 */
 227#define bio_get(bio)    atomic_inc(&(bio)->bi_cnt)
 228
 229
 230/*
 231 * A bio_pair is used when we need to split a bio.
 232 * This can only happen for a bio that refers to just one
 233 * page of data, and in the unusual situation when the
 234 * page crosses a chunk/device boundary
 235 *
 236 * The address of the master bio is stored in bio1.bi_private
 237 * The address of the pool the pair was allocated from is stored
 238 *   in bio2.bi_private
 239 */
 240struct bio_pair {
 241        struct bio      bio1, bio2;
 242        struct bio_vec  bv1, bv2;
 243        atomic_t        cnt;
 244        int             error;
 245};
 246extern struct bio_pair *bio_split(struct bio *bi, mempool_t *pool,
 247                                  int first_sectors);
 248extern mempool_t *bio_split_pool;
 249extern void bio_pair_release(struct bio_pair *dbio);
 250
 251extern struct bio *bio_alloc(int, int);
 252extern void bio_put(struct bio *);
 253
 254extern void bio_endio(struct bio *, unsigned int, int);
 255struct request_queue;
 256extern int bio_phys_segments(struct request_queue *, struct bio *);
 257extern int bio_hw_segments(struct request_queue *, struct bio *);
 258
 259extern void __bio_clone(struct bio *, struct bio *);
 260extern struct bio *bio_clone(struct bio *, int);
 261
 262extern void bio_init(struct bio *);
 263
 264extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
 265extern int bio_get_nr_vecs(struct block_device *);
 266extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
 267                                unsigned long, unsigned int, int);
 268extern void bio_unmap_user(struct bio *);
 269extern void bio_set_pages_dirty(struct bio *bio);
 270extern void bio_check_pages_dirty(struct bio *bio);
 271extern struct bio *bio_copy_user(struct request_queue *, unsigned long, unsigned int, int);
 272extern int bio_uncopy_user(struct bio *);
 273
 274#ifdef CONFIG_HIGHMEM
 275/*
 276 * remember to add offset! and never ever reenable interrupts between a
 277 * bvec_kmap_irq and bvec_kunmap_irq!!
 278 *
 279 * This function MUST be inlined - it plays with the CPU interrupt flags.
 280 * Hence the `extern inline'.
 281 */
 282extern inline char *bvec_kmap_irq(struct bio_vec *bvec, unsigned long *flags)
 283{
 284        unsigned long addr;
 285
 286        /*
 287         * might not be a highmem page, but the preempt/irq count
 288         * balancing is a lot nicer this way
 289         */
 290        local_irq_save(*flags);
 291        addr = (unsigned long) kmap_atomic(bvec->bv_page, KM_BIO_SRC_IRQ);
 292
 293        BUG_ON(addr & ~PAGE_MASK);
 294
 295        return (char *) addr + bvec->bv_offset;
 296}
 297
 298extern inline void bvec_kunmap_irq(char *buffer, unsigned long *flags)
 299{
 300        unsigned long ptr = (unsigned long) buffer & PAGE_MASK;
 301
 302        kunmap_atomic((void *) ptr, KM_BIO_SRC_IRQ);
 303        local_irq_restore(*flags);
 304}
 305
 306#else
 307#define bvec_kmap_irq(bvec, flags)      (page_address((bvec)->bv_page) + (bvec)->bv_offset)
 308#define bvec_kunmap_irq(buf, flags)     do { *(flags) = 0; } while (0)
 309#endif
 310
 311extern inline char *__bio_kmap_irq(struct bio *bio, unsigned short idx,
 312                                   unsigned long *flags)
 313{
 314        return bvec_kmap_irq(bio_iovec_idx(bio, idx), flags);
 315}
 316#define __bio_kunmap_irq(buf, flags)    bvec_kunmap_irq(buf, flags)
 317
 318#define bio_kmap_irq(bio, flags) \
 319        __bio_kmap_irq((bio), (bio)->bi_idx, (flags))
 320#define bio_kunmap_irq(buf,flags)       __bio_kunmap_irq(buf, flags)
 321
 322#endif /* __LINUX_BIO_H */
 323