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/kernel.h>
  11 #include <linux/bug.h>
  12 #include <linux/errno.h>
  13 #include <linux/mm.h>
  14
  15 /*
  16  * was unsigned short, but we might as well be ready for > 64kB I/O pages
  17  */
  18 struct bio_vec {
  19         struct page     *bv_page;
  20         unsigned int    bv_len;
  21         unsigned int    bv_offset;
  22 };
  23
  24 struct bvec_iter {
  25         sector_t                bi_sector;      /* device address in 512 byte
  26                                                    sectors */
  27         unsigned int            bi_size;        /* residual I/O count */
  28
  29         unsigned int            bi_idx;         /* current index into bvl_vec */
  30
  31         unsigned int            bi_bvec_done;   /* number of bytes completed in
  32                                                    current bvec */
  33 };
  34
  35 struct bvec_iter_all {
  36         struct bio_vec  bv;
  37         int             idx;
  38         unsigned        done;
  39 };
  40
  41 /*
  42  * various member access, note that bio_data should of course not be used
  43  * on highmem page vectors
  44  */
  45 #define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])
  46
  47 /* multi-page (mp_bvec) helpers */
  48 #define mp_bvec_iter_page(bvec, iter)                           \
  49         (__bvec_iter_bvec((bvec), (iter))->bv_page)
  50
  51 #define mp_bvec_iter_len(bvec, iter)                            \
  52         min((iter).bi_size,                                     \
  53             __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
  54
  55 #define mp_bvec_iter_offset(bvec, iter)                         \
  56         (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
  57
  58 #define mp_bvec_iter_page_idx(bvec, iter)                       \
  59         (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
  60
  61 #define mp_bvec_iter_bvec(bvec, iter)                           \
  62 ((struct bio_vec) {                                             \
  63         .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
  64         .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
  65         .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
  66 })
  67
  68 /* For building single-page bvec in flight */
  69  #define bvec_iter_offset(bvec, iter)                           \
  70         (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
  71
  72 #define bvec_iter_len(bvec, iter)                               \
  73         min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),               \
  74               PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
  75
  76 #define bvec_iter_page(bvec, iter)                              \
  77         (mp_bvec_iter_page((bvec), (iter)) +                    \
  78          mp_bvec_iter_page_idx((bvec), (iter)))
  79
  80 #define bvec_iter_bvec(bvec, iter)                              \
  81 ((struct bio_vec) {                                             \
  82         .bv_page        = bvec_iter_page((bvec), (iter)),       \
  83         .bv_len         = bvec_iter_len((bvec), (iter)),        \
  84         .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
  85 })
  86
  87 static inline bool bvec_iter_advance(const struct bio_vec *bv,
  88                 struct bvec_iter *iter, unsigned bytes)
  89 {
  90         unsigned int idx = iter->bi_idx;
  91
  92         if (WARN_ONCE(bytes > iter->bi_size,
  93                      "Attempted to advance past end of bvec iter\n")) {
  94                 iter->bi_size = 0;
  95                 return false;
  96         }
  97
  98         iter->bi_size -= bytes;
  99         bytes += iter->bi_bvec_done;
 100
 101         while (bytes && bytes >= bv[idx].bv_len) {
 102                 bytes -= bv[idx].bv_len;
 103                 idx++;
 104         }
 105
 106         iter->bi_idx = idx;
 107         iter->bi_bvec_done = bytes;
 108         return true;
 109 }
 110
 111 #define for_each_bvec(bvl, bio_vec, iter, start)                        \
 112         for (iter = (start);                                            \
 113              (iter).bi_size &&                                          \
 114                 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
 115              bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
 116
 117 /* for iterating one bio from start to end */
 118 #define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
 119 {                                                                       \
 120         .bi_sector      = 0,                                            \
 121         .bi_size        = UINT_MAX,                                     \
 122         .bi_idx         = 0,                                            \
 123         .bi_bvec_done   = 0,                                            \
 124 }
 125
 126 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 127 {
 128         iter_all->done = 0;
 129         iter_all->idx = 0;
 130
 131         return &iter_all->bv;
 132 }
 133
 134 static inline void bvec_advance(const struct bio_vec *bvec,
 135                                 struct bvec_iter_all *iter_all)
 136 {
 137         struct bio_vec *bv = &iter_all->bv;
 138
 139         if (iter_all->done) {
 140                 bv->bv_page++;
 141                 bv->bv_offset = 0;
 142         } else {
 143                 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
 144                 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
 145         }
 146         bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
 147                            bvec->bv_len - iter_all->done);
 148         iter_all->done += bv->bv_len;
 149
 150         if (iter_all->done == bvec->bv_len) {
 151                 iter_all->idx++;
 152                 iter_all->done = 0;
 153         }
 154 }
 155
 156 /*
 157  * Get the last single-page segment from the multi-page bvec and store it
 158  * in @seg
 159  */
 160 static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
 161                                         struct bio_vec *seg)
 162 {
 163         unsigned total = bvec->bv_offset + bvec->bv_len;
 164         unsigned last_page = (total - 1) / PAGE_SIZE;
 165
 166         seg->bv_page = bvec->bv_page + last_page;
 167
 168         /* the whole segment is inside the last page */
 169         if (bvec->bv_offset >= last_page * PAGE_SIZE) {
 170                 seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
 171                 seg->bv_len = bvec->bv_len;
 172         } else {
 173                 seg->bv_offset = 0;
 174                 seg->bv_len = total - last_page * PAGE_SIZE;
 175         }
 176 }
 177
 178 #endif /* __LINUX_BVEC_ITER_H */