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/*
* bvec iterator
*
* Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
*
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public Licens
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-
*/
#ifndef __LINUX_BVEC_ITER_H
#define __LINUX_BVEC_ITER_H
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/errno.h>
#include <linux/mm.h>
/*
* was unsigned short, but we might as well be ready for > 64kB I/O pages
*/
struct bio_vec {
struct page *bv_page;
unsigned int bv_len;
unsigned int bv_offset;
};
struct bvec_iter {
sector_t bi_sector; /* device address in 512 byte
sectors */
unsigned int bi_size; /* residual I/O count */
unsigned int bi_idx; /* current index into bvl_vec */
unsigned int bi_done; /* number of bytes completed */
unsigned int bi_bvec_done; /* number of bytes completed in
current bvec */
};
/*
* various member access, note that bio_data should of course not be used
* on highmem page vectors
*/
#define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
/* multi-page (mp_bvec) helpers */
#define mp_bvec_iter_page(bvec, iter) \
(__bvec_iter_bvec((bvec), (iter))->bv_page)
#define mp_bvec_iter_len(bvec, iter) \
min((iter).bi_size, \
__bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
#define mp_bvec_iter_offset(bvec, iter) \
(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
#define mp_bvec_iter_page_idx(bvec, iter) \
(mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
#define mp_bvec_iter_bvec(bvec, iter) \
((struct bio_vec) { \
.bv_page = mp_bvec_iter_page((bvec), (iter)), \
.bv_len = mp_bvec_iter_len((bvec), (iter)), \
.bv_offset = mp_bvec_iter_offset((bvec), (iter)), \
})
/* For building single-page bvec in flight */
#define bvec_iter_offset(bvec, iter) \
(mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
#define bvec_iter_len(bvec, iter) \
min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \
PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
#define bvec_iter_page(bvec, iter) \
nth_page(mp_bvec_iter_page((bvec), (iter)), \
mp_bvec_iter_page_idx((bvec), (iter)))
#define bvec_iter_bvec(bvec, iter) \
((struct bio_vec) { \
.bv_page = bvec_iter_page((bvec), (iter)), \
.bv_len = bvec_iter_len((bvec), (iter)), \
.bv_offset = bvec_iter_offset((bvec), (iter)), \
})
static inline bool bvec_iter_advance(const struct bio_vec *bv,
struct bvec_iter *iter, unsigned bytes)
{
if (WARN_ONCE(bytes > iter->bi_size,
"Attempted to advance past end of bvec iter\n")) {
iter->bi_size = 0;
return false;
}
while (bytes) {
unsigned iter_len = bvec_iter_len(bv, *iter);
unsigned len = min(bytes, iter_len);
bytes -= len;
iter->bi_size -= len;
iter->bi_bvec_done += len;
iter->bi_done += len;
if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
iter->bi_bvec_done = 0;
iter->bi_idx++;
}
}
return true;
}
static inline bool bvec_iter_rewind(const struct bio_vec *bv,
struct bvec_iter *iter,
unsigned int bytes)
{
while (bytes) {
unsigned len = min(bytes, iter->bi_bvec_done);
if (iter->bi_bvec_done == 0) {
if (WARN_ONCE(iter->bi_idx == 0,
"Attempted to rewind iter beyond "
"bvec's boundaries\n")) {
return false;
}
iter->bi_idx--;
iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
continue;
}
bytes -= len;
iter->bi_size += len;
iter->bi_bvec_done -= len;
}
return true;
}
static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
{
iter->bi_bvec_done = 0;
iter->bi_idx++;
}
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
(bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
(bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
#endif /* __LINUX_BVEC_ITER_H */
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