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80f162ff06
bvec_iter_advance() only writes the parameter of iterator, so the base address of bvec can be marked as const safely. Without the change, we can see compiling warning in the following patch for implementing iterate_bvec(): lib/iov_iter.c with bvec iterator. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@canonical.com> Tested-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
97 lines
2.7 KiB
C
97 lines
2.7 KiB
C
/*
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* bvec iterator
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*
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* Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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*
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public Licens
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-
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*/
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#ifndef __LINUX_BVEC_ITER_H
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#define __LINUX_BVEC_ITER_H
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#include <linux/kernel.h>
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#include <linux/bug.h>
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/*
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* was unsigned short, but we might as well be ready for > 64kB I/O pages
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*/
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struct bio_vec {
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struct page *bv_page;
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unsigned int bv_len;
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unsigned int bv_offset;
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};
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struct bvec_iter {
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sector_t bi_sector; /* device address in 512 byte
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sectors */
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unsigned int bi_size; /* residual I/O count */
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unsigned int bi_idx; /* current index into bvl_vec */
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unsigned int bi_bvec_done; /* number of bytes completed in
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current bvec */
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};
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/*
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* various member access, note that bio_data should of course not be used
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* on highmem page vectors
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*/
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#define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
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#define bvec_iter_page(bvec, iter) \
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(__bvec_iter_bvec((bvec), (iter))->bv_page)
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#define bvec_iter_len(bvec, iter) \
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min((iter).bi_size, \
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__bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
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#define bvec_iter_offset(bvec, iter) \
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(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
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#define bvec_iter_bvec(bvec, iter) \
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((struct bio_vec) { \
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.bv_page = bvec_iter_page((bvec), (iter)), \
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.bv_len = bvec_iter_len((bvec), (iter)), \
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.bv_offset = bvec_iter_offset((bvec), (iter)), \
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})
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static inline void bvec_iter_advance(const struct bio_vec *bv,
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struct bvec_iter *iter,
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unsigned bytes)
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{
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WARN_ONCE(bytes > iter->bi_size,
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"Attempted to advance past end of bvec iter\n");
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while (bytes) {
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unsigned len = min(bytes, bvec_iter_len(bv, *iter));
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bytes -= len;
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iter->bi_size -= len;
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iter->bi_bvec_done += len;
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if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
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iter->bi_bvec_done = 0;
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iter->bi_idx++;
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}
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}
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}
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#define for_each_bvec(bvl, bio_vec, iter, start) \
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for (iter = (start); \
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(iter).bi_size && \
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((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
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bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
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#endif /* __LINUX_BVEC_ITER_H */
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