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![Christoph Hellwig](/assets/img/avatar_default.png)
When Jens merged my commit to only allow contiguous page structs in a
bio_vec with Ming's 5.1 fix to ensue the bvec length didn't overflow
we failed to keep the removal of the expensive nth_page calls. This
commits adds them back as intended.
Fixes: 5c61ee2cd5
("Merge tag 'v5.1-rc6' into for-5.2/block")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
180 lines
4.5 KiB
C
180 lines
4.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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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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#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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#include <linux/errno.h>
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#include <linux/mm.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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struct bvec_iter_all {
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struct bio_vec bv;
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int idx;
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unsigned done;
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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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/* multi-page (mp_bvec) helpers */
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#define mp_bvec_iter_page(bvec, iter) \
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(__bvec_iter_bvec((bvec), (iter))->bv_page)
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#define mp_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 mp_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 mp_bvec_iter_page_idx(bvec, iter) \
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(mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
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#define mp_bvec_iter_bvec(bvec, iter) \
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((struct bio_vec) { \
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.bv_page = mp_bvec_iter_page((bvec), (iter)), \
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.bv_len = mp_bvec_iter_len((bvec), (iter)), \
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.bv_offset = mp_bvec_iter_offset((bvec), (iter)), \
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})
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/* For building single-page bvec in flight */
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#define bvec_iter_offset(bvec, iter) \
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(mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
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#define bvec_iter_len(bvec, iter) \
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min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \
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PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
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#define bvec_iter_page(bvec, iter) \
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(mp_bvec_iter_page((bvec), (iter)) + \
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mp_bvec_iter_page_idx((bvec), (iter)))
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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 bool bvec_iter_advance(const struct bio_vec *bv,
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struct bvec_iter *iter, unsigned bytes)
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{
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if (WARN_ONCE(bytes > iter->bi_size,
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"Attempted to advance past end of bvec iter\n")) {
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iter->bi_size = 0;
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return false;
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}
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while (bytes) {
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const struct bio_vec *cur = bv + iter->bi_idx;
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unsigned len = min3(bytes, iter->bi_size,
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cur->bv_len - iter->bi_bvec_done);
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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 == cur->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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return true;
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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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/* for iterating one bio from start to end */
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#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
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{ \
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.bi_sector = 0, \
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.bi_size = UINT_MAX, \
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.bi_idx = 0, \
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.bi_bvec_done = 0, \
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}
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static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
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{
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iter_all->done = 0;
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iter_all->idx = 0;
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return &iter_all->bv;
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}
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static inline void bvec_advance(const struct bio_vec *bvec,
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struct bvec_iter_all *iter_all)
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{
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struct bio_vec *bv = &iter_all->bv;
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if (iter_all->done) {
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bv->bv_page++;
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bv->bv_offset = 0;
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} else {
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bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
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bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
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}
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bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
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bvec->bv_len - iter_all->done);
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iter_all->done += bv->bv_len;
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if (iter_all->done == bvec->bv_len) {
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iter_all->idx++;
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iter_all->done = 0;
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}
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}
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/*
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* Get the last single-page segment from the multi-page bvec and store it
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* in @seg
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*/
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static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
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struct bio_vec *seg)
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{
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unsigned total = bvec->bv_offset + bvec->bv_len;
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unsigned last_page = (total - 1) / PAGE_SIZE;
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seg->bv_page = bvec->bv_page + last_page;
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/* the whole segment is inside the last page */
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if (bvec->bv_offset >= last_page * PAGE_SIZE) {
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seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
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seg->bv_len = bvec->bv_len;
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} else {
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seg->bv_offset = 0;
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seg->bv_len = total - last_page * PAGE_SIZE;
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}
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}
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#endif /* __LINUX_BVEC_ITER_H */
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