LXR linux/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
  26/*
  27 * was unsigned short, but we might as well be ready for > 64kB I/O pages
  28 */
  29struct bio_vec {
  30        struct page     *bv_page;
  31        unsigned int    bv_len;
  32        unsigned int    bv_offset;
  33};
  34
  35struct bvec_iter {
  36        sector_t                bi_sector;      /* device address in 512 byte
  37                                                   sectors */
  38        unsigned int            bi_size;        /* residual I/O count */
  39
  40        unsigned int            bi_idx;         /* current index into bvl_vec */
  41
  42        unsigned int            bi_bvec_done;   /* number of bytes completed in
  43                                                   current bvec */
  44};
  45
  46/*
  47 * various member access, note that bio_data should of course not be used
  48 * on highmem page vectors
  49 */
  50#define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])
  51
  52#define bvec_iter_page(bvec, iter)                              \
  53        (__bvec_iter_bvec((bvec), (iter))->bv_page)
  54
  55#define bvec_iter_len(bvec, iter)                               \
  56        min((iter).bi_size,                                     \
  57            __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
  58
  59#define bvec_iter_offset(bvec, iter)                            \
  60        (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
  61
  62#define bvec_iter_bvec(bvec, iter)                              \
  63((struct bio_vec) {                                             \
  64        .bv_page        = bvec_iter_page((bvec), (iter)),       \
  65        .bv_len         = bvec_iter_len((bvec), (iter)),        \
  66        .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
  67})
  68
  69static inline void bvec_iter_advance(const struct bio_vec *bv,
  70                                     struct bvec_iter *iter,
  71                                     unsigned bytes)
  72{
  73        WARN_ONCE(bytes > iter->bi_size,
  74                  "Attempted to advance past end of bvec iter\n");
  75
  76        while (bytes) {
  77                unsigned iter_len = bvec_iter_len(bv, *iter);
  78                unsigned len = min(bytes, iter_len);
  79
  80                bytes -= len;
  81                iter->bi_size -= len;
  82                iter->bi_bvec_done += len;
  83
  84                if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
  85                        iter->bi_bvec_done = 0;
  86                        iter->bi_idx++;
  87                }
  88        }
  89}
  90
  91#define for_each_bvec(bvl, bio_vec, iter, start)                        \
  92        for (iter = (start);                                            \
  93             (iter).bi_size &&                                          \
  94                ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
  95             bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
  96
  97#endif /* __LINUX_BVEC_ITER_H */
  98