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![Ming Lei](/assets/img/avatar_default.png)
'struct bvec_iter' is embedded into 'struct bio', define it as packed so that we can get one extra 4bytes for other uses without expanding bio. 'struct bvec_iter' is often allocated on stack, so making it packed doesn't affect performance. Also I have run io_uring on both nvme/null_blk, and not observe performance effect in this way. Suggested-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Christoph Hellwig <hch@lst.de> Tested-by: Mark Wunderlich <mark.wunderlich@intel.com> Link: https://lore.kernel.org/r/20211012111226.760968-14-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
244 lines
6.2 KiB
C
244 lines
6.2 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_H
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#define __LINUX_BVEC_H
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#include <linux/highmem.h>
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#include <linux/bug.h>
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#include <linux/errno.h>
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#include <linux/limits.h>
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#include <linux/minmax.h>
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#include <linux/mm.h>
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#include <linux/types.h>
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struct page;
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/**
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* struct bio_vec - a contiguous range of physical memory addresses
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* @bv_page: First page associated with the address range.
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* @bv_len: Number of bytes in the address range.
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* @bv_offset: Start of the address range relative to the start of @bv_page.
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*
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* The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
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*
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* nth_page(@bv_page, n) == @bv_page + n
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*
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* This holds because page_is_mergeable() checks the above property.
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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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} __packed;
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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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unsigned int idx = iter->bi_idx;
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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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iter->bi_size -= bytes;
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bytes += iter->bi_bvec_done;
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while (bytes && bytes >= bv[idx].bv_len) {
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bytes -= bv[idx].bv_len;
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idx++;
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}
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iter->bi_idx = idx;
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iter->bi_bvec_done = bytes;
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return true;
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}
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/*
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* A simpler version of bvec_iter_advance(), @bytes should not span
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* across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
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*/
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static inline void bvec_iter_advance_single(const struct bio_vec *bv,
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struct bvec_iter *iter, unsigned int bytes)
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{
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unsigned int done = iter->bi_bvec_done + bytes;
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if (done == bv[iter->bi_idx].bv_len) {
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done = 0;
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iter->bi_idx++;
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}
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iter->bi_bvec_done = done;
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iter->bi_size -= bytes;
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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_single((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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* bvec_kmap_local - map a bvec into the kernel virtual address space
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* @bvec: bvec to map
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*
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* Must be called on single-page bvecs only. Call kunmap_local on the returned
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* address to unmap.
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*/
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static inline void *bvec_kmap_local(struct bio_vec *bvec)
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{
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return kmap_local_page(bvec->bv_page) + bvec->bv_offset;
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}
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/**
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* memcpy_from_bvec - copy data from a bvec
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* @bvec: bvec to copy from
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*
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* Must be called on single-page bvecs only.
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*/
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static inline void memcpy_from_bvec(char *to, struct bio_vec *bvec)
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{
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memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, bvec->bv_len);
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}
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/**
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* memcpy_to_bvec - copy data to a bvec
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* @bvec: bvec to copy to
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*
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* Must be called on single-page bvecs only.
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*/
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static inline void memcpy_to_bvec(struct bio_vec *bvec, const char *from)
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{
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memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, bvec->bv_len);
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}
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/**
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* memzero_bvec - zero all data in a bvec
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* @bvec: bvec to zero
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*
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* Must be called on single-page bvecs only.
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*/
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static inline void memzero_bvec(struct bio_vec *bvec)
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{
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memzero_page(bvec->bv_page, bvec->bv_offset, bvec->bv_len);
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}
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/**
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* bvec_virt - return the virtual address for a bvec
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* @bvec: bvec to return the virtual address for
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*
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* Note: the caller must ensure that @bvec->bv_page is not a highmem page.
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*/
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static inline void *bvec_virt(struct bio_vec *bvec)
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{
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WARN_ON_ONCE(PageHighMem(bvec->bv_page));
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return page_address(bvec->bv_page) + bvec->bv_offset;
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}
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#endif /* __LINUX_BVEC_H */
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