include/linux/bvec.h

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