LXR linux/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 */
  18struct bio_vec {
  19        struct page     *bv_page;
  20        unsigned int    bv_len;
  21        unsigned int    bv_offset;
  22};
  23
  24struct 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
  35struct 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
  87static inline bool bvec_iter_advance(const struct bio_vec *bv,
  88                struct bvec_iter *iter, unsigned bytes)
  89{
  90        if (WARN_ONCE(bytes > iter->bi_size,
  91                     "Attempted to advance past end of bvec iter\n")) {
  92                iter->bi_size = 0;
  93                return false;
  94        }
  95
  96        while (bytes) {
  97                const struct bio_vec *cur = bv + iter->bi_idx;
  98                unsigned len = min3(bytes, iter->bi_size,
  99                                    cur->bv_len - iter->bi_bvec_done);
 100
 101                bytes -= len;
 102                iter->bi_size -= len;
 103                iter->bi_bvec_done += len;
 104
 105                if (iter->bi_bvec_done == cur->bv_len) {
 106                        iter->bi_bvec_done = 0;
 107                        iter->bi_idx++;
 108                }
 109        }
 110        return true;
 111}
 112
 113#define for_each_bvec(bvl, bio_vec, iter, start)                        \
 114        for (iter = (start);                                            \
 115             (iter).bi_size &&                                          \
 116                ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
 117             bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
 118
 119/* for iterating one bio from start to end */
 120#define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
 121{                                                                       \
 122        .bi_sector      = 0,                                            \
 123        .bi_size        = UINT_MAX,                                     \
 124        .bi_idx         = 0,                                            \
 125        .bi_bvec_done   = 0,                                            \
 126}
 127
 128static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 129{
 130        iter_all->done = 0;
 131        iter_all->idx = 0;
 132
 133        return &iter_all->bv;
 134}
 135
 136static inline void bvec_advance(const struct bio_vec *bvec,
 137                                struct bvec_iter_all *iter_all)
 138{
 139        struct bio_vec *bv = &iter_all->bv;
 140
 141        if (iter_all->done) {
 142                bv->bv_page++;
 143                bv->bv_offset = 0;
 144        } else {
 145                bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
 146                bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
 147        }
 148        bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
 149                           bvec->bv_len - iter_all->done);
 150        iter_all->done += bv->bv_len;
 151
 152        if (iter_all->done == bvec->bv_len) {
 153                iter_all->idx++;
 154                iter_all->done = 0;
 155        }
 156}
 157
 158/*
 159 * Get the last single-page segment from the multi-page bvec and store it
 160 * in @seg
 161 */
 162static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
 163                                        struct bio_vec *seg)
 164{
 165        unsigned total = bvec->bv_offset + bvec->bv_len;
 166        unsigned last_page = (total - 1) / PAGE_SIZE;
 167
 168        seg->bv_page = bvec->bv_page + last_page;
 169
 170        /* the whole segment is inside the last page */
 171        if (bvec->bv_offset >= last_page * PAGE_SIZE) {
 172                seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
 173                seg->bv_len = bvec->bv_len;
 174        } else {
 175                seg->bv_offset = 0;
 176                seg->bv_len = total - last_page * PAGE_SIZE;
 177        }
 178}
 179
 180#endif /* __LINUX_BVEC_ITER_H */
 181