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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_bvec_done; /* number of bytes completed in
current bvec */
};
struct bvec_iter_all {
struct bio_vec bv;
int idx;
unsigned done;
};
static inline struct page *bvec_nth_page(struct page *page, int idx)
{
return idx == 0 ? page : nth_page(page, idx);
}
/*
* 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) \
bvec_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;
if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
iter->bi_bvec_done = 0;
iter->bi_idx++;
}
}
return true;
}
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
/* for iterating one bio from start to end */
#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
{ \
.bi_sector = 0, \
.bi_size = UINT_MAX, \
.bi_idx = 0, \
.bi_bvec_done = 0, \
}
static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
{
iter_all->bv.bv_page = NULL;
iter_all->done = 0;
return &iter_all->bv;
}
static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
struct bvec_iter_all *iter_all)
{
struct bio_vec *bv = &iter_all->bv;
if (bv->bv_page) {
bv->bv_page = nth_page(bv->bv_page, 1);
bv->bv_offset = 0;
} else {
bv->bv_page = bvec->bv_page;
bv->bv_offset = bvec->bv_offset;
}
bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
bvec->bv_len - iter_all->done);
}
/*
* Get the last single-page segment from the multi-page bvec and store it
* in @seg
*/
static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
struct bio_vec *seg)
{
unsigned total = bvec->bv_offset + bvec->bv_len;
unsigned last_page = (total - 1) / PAGE_SIZE;
seg->bv_page = bvec_nth_page(bvec->bv_page, last_page);
/* the whole segment is inside the last page */
if (bvec->bv_offset >= last_page * PAGE_SIZE) {
seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
seg->bv_len = bvec->bv_len;
} else {
seg->bv_offset = 0;
seg->bv_len = total - last_page * PAGE_SIZE;
}
}
#endif /* __LINUX_BVEC_ITER_H */
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