include/linux/bvec.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * bvec iterator
   4  *
   5  * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
   6  */
   7 #ifndef __LINUX_BVEC_ITER_H
   8 #define __LINUX_BVEC_ITER_H
   9
  10 #include <linux/bug.h>
  11 #include <linux/errno.h>
  12 #include <linux/limits.h>
  13 #include <linux/minmax.h>
  14 #include <linux/mm.h>
  15 #include <linux/types.h>
  16
  17 struct page;
  18
  19 /**
  20  * struct bio_vec - a contiguous range of physical memory addresses
  21  * @bv_page:   First page associated with the address range.
  22  * @bv_len:    Number of bytes in the address range.
  23  * @bv_offset: Start of the address range relative to the start of @bv_page.
  24  *
  25  * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
  26  *
  27  *   nth_page(@bv_page, n) == @bv_page + n
  28  *
  29  * This holds because page_is_mergeable() checks the above property.
  30  */
  31 struct bio_vec {
  32         struct page     *bv_page;
  33         unsigned int    bv_len;
  34         unsigned int    bv_offset;
  35 };
  36
  37 struct bvec_iter {
  38         sector_t                bi_sector;      /* device address in 512 byte
  39                                                    sectors */
  40         unsigned int            bi_size;        /* residual I/O count */
  41
  42         unsigned int            bi_idx;         /* current index into bvl_vec */
  43
  44         unsigned int            bi_bvec_done;   /* number of bytes completed in
  45                                                    current bvec */
  46 };
  47
  48 struct bvec_iter_all {
  49         struct bio_vec  bv;
  50         int             idx;
  51         unsigned        done;
  52 };
  53
  54 /*
  55  * various member access, note that bio_data should of course not be used
  56  * on highmem page vectors
  57  */
  58 #define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])
  59
  60 /* multi-page (mp_bvec) helpers */
  61 #define mp_bvec_iter_page(bvec, iter)                           \
  62         (__bvec_iter_bvec((bvec), (iter))->bv_page)
  63
  64 #define mp_bvec_iter_len(bvec, iter)                            \
  65         min((iter).bi_size,                                     \
  66             __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
  67
  68 #define mp_bvec_iter_offset(bvec, iter)                         \
  69         (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
  70
  71 #define mp_bvec_iter_page_idx(bvec, iter)                       \
  72         (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
  73
  74 #define mp_bvec_iter_bvec(bvec, iter)                           \
  75 ((struct bio_vec) {                                             \
  76         .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
  77         .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
  78         .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
  79 })
  80
  81 /* For building single-page bvec in flight */
  82  #define bvec_iter_offset(bvec, iter)                           \
  83         (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
  84
  85 #define bvec_iter_len(bvec, iter)                               \
  86         min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),               \
  87               PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
  88
  89 #define bvec_iter_page(bvec, iter)                              \
  90         (mp_bvec_iter_page((bvec), (iter)) +                    \
  91          mp_bvec_iter_page_idx((bvec), (iter)))
  92
  93 #define bvec_iter_bvec(bvec, iter)                              \
  94 ((struct bio_vec) {                                             \
  95         .bv_page        = bvec_iter_page((bvec), (iter)),       \
  96         .bv_len         = bvec_iter_len((bvec), (iter)),        \
  97         .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
  98 })
  99
 100 static inline bool bvec_iter_advance(const struct bio_vec *bv,
 101                 struct bvec_iter *iter, unsigned bytes)
 102 {
 103         unsigned int idx = iter->bi_idx;
 104
 105         if (WARN_ONCE(bytes > iter->bi_size,
 106                      "Attempted to advance past end of bvec iter\n")) {
 107                 iter->bi_size = 0;
 108                 return false;
 109         }
 110
 111         iter->bi_size -= bytes;
 112         bytes += iter->bi_bvec_done;
 113
 114         while (bytes && bytes >= bv[idx].bv_len) {
 115                 bytes -= bv[idx].bv_len;
 116                 idx++;
 117         }
 118
 119         iter->bi_idx = idx;
 120         iter->bi_bvec_done = bytes;
 121         return true;
 122 }
 123
 124 /*
 125  * A simpler version of bvec_iter_advance(), @bytes should not span
 126  * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
 127  */
 128 static inline void bvec_iter_advance_single(const struct bio_vec *bv,
 129                                 struct bvec_iter *iter, unsigned int bytes)
 130 {
 131         unsigned int done = iter->bi_bvec_done + bytes;
 132
 133         if (done == bv[iter->bi_idx].bv_len) {
 134                 done = 0;
 135                 iter->bi_idx++;
 136         }
 137         iter->bi_bvec_done = done;
 138         iter->bi_size -= bytes;
 139 }
 140
 141 #define for_each_bvec(bvl, bio_vec, iter, start)                        \
 142         for (iter = (start);                                            \
 143              (iter).bi_size &&                                          \
 144                 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
 145              bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))
 146
 147 /* for iterating one bio from start to end */
 148 #define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
 149 {                                                                       \
 150         .bi_sector      = 0,                                            \
 151         .bi_size        = UINT_MAX,                                     \
 152         .bi_idx         = 0,                                            \
 153         .bi_bvec_done   = 0,                                            \
 154 }
 155
 156 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 157 {
 158         iter_all->done = 0;
 159         iter_all->idx = 0;
 160
 161         return &iter_all->bv;
 162 }
 163
 164 static inline void bvec_advance(const struct bio_vec *bvec,
 165                                 struct bvec_iter_all *iter_all)
 166 {
 167         struct bio_vec *bv = &iter_all->bv;
 168
 169         if (iter_all->done) {
 170                 bv->bv_page++;
 171                 bv->bv_offset = 0;
 172         } else {
 173                 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
 174                 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
 175         }
 176         bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
 177                            bvec->bv_len - iter_all->done);
 178         iter_all->done += bv->bv_len;
 179
 180         if (iter_all->done == bvec->bv_len) {
 181                 iter_all->idx++;
 182                 iter_all->done = 0;
 183         }
 184 }
 185
 186 #endif /* __LINUX_BVEC_ITER_H */