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 * 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 */
  27struct bio_vec {
  28        struct page     *bv_page;
  29        unsigned int    bv_len;
  30        unsigned int    bv_offset;
  31};
  32
  33struct 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
  44struct 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
  96static 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
 120static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
 121{
 122        iter->bi_bvec_done = 0;
 123        iter->bi_idx++;
 124}
 125
 126#define for_each_bvec(bvl, bio_vec, iter, start)                        \
 127        for (iter = (start);                                            \
 128             (iter).bi_size &&                                          \
 129                ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
 130             (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
 131                     (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
 132
 133/* for iterating one bio from start to end */
 134#define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
 135{                                                                       \
 136        .bi_sector      = 0,                                            \
 137        .bi_size        = UINT_MAX,                                     \
 138        .bi_idx         = 0,                                            \
 139        .bi_bvec_done   = 0,                                            \
 140}
 141
 142static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 143{
 144        iter_all->done = 0;
 145        iter_all->idx = 0;
 146
 147        return &iter_all->bv;
 148}
 149
 150static inline void bvec_advance(const struct bio_vec *bvec,
 151                                struct bvec_iter_all *iter_all)
 152{
 153        struct bio_vec *bv = &iter_all->bv;
 154
 155        if (iter_all->done) {
 156                bv->bv_page++;
 157                bv->bv_offset = 0;
 158        } else {
 159                bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
 160                bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
 161        }
 162        bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
 163                           bvec->bv_len - iter_all->done);
 164        iter_all->done += bv->bv_len;
 165
 166        if (iter_all->done == bvec->bv_len) {
 167                iter_all->idx++;
 168                iter_all->done = 0;
 169        }
 170}
 171
 172#endif /* __LINUX_BVEC_ITER_H */
 173