include/linux/bvec.h

   1 /*
   2  * bvec iterator
   3  *
   4  * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
   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_BVEC_ITER_H
  21 #define __LINUX_BVEC_ITER_H
  22
  23 #include <linux/kernel.h>
  24 #include <linux/bug.h>
  25 #include <linux/errno.h>
  26 #include <linux/mm.h>
  27
  28 /*
  29  * was unsigned short, but we might as well be ready for > 64kB I/O pages
  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 static inline struct page *bvec_nth_page(struct page *page, int idx)
  55 {
  56         return idx == 0 ? page : nth_page(page, idx);
  57 }
  58
  59 /*
  60  * various member access, note that bio_data should of course not be used
  61  * on highmem page vectors
  62  */
  63 #define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])
  64
  65 /* multi-page (mp_bvec) helpers */
  66 #define mp_bvec_iter_page(bvec, iter)                           \
  67         (__bvec_iter_bvec((bvec), (iter))->bv_page)
  68
  69 #define mp_bvec_iter_len(bvec, iter)                            \
  70         min((iter).bi_size,                                     \
  71             __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
  72
  73 #define mp_bvec_iter_offset(bvec, iter)                         \
  74         (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
  75
  76 #define mp_bvec_iter_page_idx(bvec, iter)                       \
  77         (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
  78
  79 #define mp_bvec_iter_bvec(bvec, iter)                           \
  80 ((struct bio_vec) {                                             \
  81         .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
  82         .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
  83         .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
  84 })
  85
  86 /* For building single-page bvec in flight */
  87  #define bvec_iter_offset(bvec, iter)                           \
  88         (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
  89
  90 #define bvec_iter_len(bvec, iter)                               \
  91         min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),               \
  92               PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
  93
  94 #define bvec_iter_page(bvec, iter)                              \
  95         bvec_nth_page(mp_bvec_iter_page((bvec), (iter)),                \
  96                       mp_bvec_iter_page_idx((bvec), (iter)))
  97
  98 #define bvec_iter_bvec(bvec, iter)                              \
  99 ((struct bio_vec) {                                             \
 100         .bv_page        = bvec_iter_page((bvec), (iter)),       \
 101         .bv_len         = bvec_iter_len((bvec), (iter)),        \
 102         .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
 103 })
 104
 105 static inline bool bvec_iter_advance(const struct bio_vec *bv,
 106                 struct bvec_iter *iter, unsigned bytes)
 107 {
 108         if (WARN_ONCE(bytes > iter->bi_size,
 109                      "Attempted to advance past end of bvec iter\n")) {
 110                 iter->bi_size = 0;
 111                 return false;
 112         }
 113
 114         while (bytes) {
 115                 const struct bio_vec *cur = bv + iter->bi_idx;
 116                 unsigned len = min3(bytes, iter->bi_size,
 117                                     cur->bv_len - iter->bi_bvec_done);
 118
 119                 bytes -= len;
 120                 iter->bi_size -= len;
 121                 iter->bi_bvec_done += len;
 122
 123                 if (iter->bi_bvec_done == cur->bv_len) {
 124                         iter->bi_bvec_done = 0;
 125                         iter->bi_idx++;
 126                 }
 127         }
 128         return true;
 129 }
 130
 131 #define for_each_bvec(bvl, bio_vec, iter, start)                        \
 132         for (iter = (start);                                            \
 133              (iter).bi_size &&                                          \
 134                 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
 135              bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
 136
 137 /* for iterating one bio from start to end */
 138 #define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
 139 {                                                                       \
 140         .bi_sector      = 0,                                            \
 141         .bi_size        = UINT_MAX,                                     \
 142         .bi_idx         = 0,                                            \
 143         .bi_bvec_done   = 0,                                            \
 144 }
 145
 146 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 147 {
 148         iter_all->bv.bv_page = NULL;
 149         iter_all->done = 0;
 150
 151         return &iter_all->bv;
 152 }
 153
 154 static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
 155                                         struct bvec_iter_all *iter_all)
 156 {
 157         struct bio_vec *bv = &iter_all->bv;
 158
 159         if (bv->bv_page) {
 160                 bv->bv_page = nth_page(bv->bv_page, 1);
 161                 bv->bv_offset = 0;
 162         } else {
 163                 bv->bv_page = bvec->bv_page;
 164                 bv->bv_offset = bvec->bv_offset;
 165         }
 166         bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
 167                            bvec->bv_len - iter_all->done);
 168 }
 169
 170 /*
 171  * Get the last single-page segment from the multi-page bvec and store it
 172  * in @seg
 173  */
 174 static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
 175                                         struct bio_vec *seg)
 176 {
 177         unsigned total = bvec->bv_offset + bvec->bv_len;
 178         unsigned last_page = (total - 1) / PAGE_SIZE;
 179
 180         seg->bv_page = bvec_nth_page(bvec->bv_page, last_page);
 181
 182         /* the whole segment is inside the last page */
 183         if (bvec->bv_offset >= last_page * PAGE_SIZE) {
 184                 seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
 185                 seg->bv_len = bvec->bv_len;
 186         } else {
 187                 seg->bv_offset = 0;
 188                 seg->bv_len = total - last_page * PAGE_SIZE;
 189         }
 190 }
 191
 192 #define mp_bvec_for_each_page(pg, bv, i)                                \
 193         for (i = (bv)->bv_offset / PAGE_SIZE;                           \
 194                 (i <= (((bv)->bv_offset + (bv)->bv_len - 1) / PAGE_SIZE)) && \
 195                 (pg = bvec_nth_page((bv)->bv_page, i)); i += 1)
 196
 197 #endif /* __LINUX_BVEC_ITER_H */