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brd: use memcpy_{to,from]_page in brd_rw_bvec 

Use the proper helpers to copy to/from potential highmem pages, which
do a local instead of atomic kmap underneath, and perform
flush_dcache_page where needed.  This also simplifies the code so much
that the separate read write helpers are not required any more.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20250428141014.2360063-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2025-04-28 07:09:51 -07:00 committed by Jens Axboe
parent 3185444f05
commit 53ec1abce7
1 changed files with 13 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
drivers/block/brd.c
View File

@ -99,43 +99,6 @@ static void brd_free_pages(struct brd_device *brd)
xa_destroy(&brd->brd_pages);
}
/*
* Copy n bytes from src to the brd starting at sector. Does not sleep.
*/
static void copy_to_brd(struct brd_device *brd, const void *src,
sector_t sector, size_t n)
{
struct page *page;
void *dst;
unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
page = brd_lookup_page(brd, sector);
BUG_ON(!page);
dst = kmap_atomic(page);
memcpy(dst + offset, src, n);
kunmap_atomic(dst);
}
/*
* Copy n bytes to dst from the brd starting at sector. Does not sleep.
*/
static void copy_from_brd(void *dst, struct brd_device *brd,
sector_t sector, size_t n)
{
struct page *page;
void *src;
unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
page = brd_lookup_page(brd, sector);
if (page) {
src = kmap_atomic(page);
memcpy(dst, src + offset, n);
kunmap_atomic(src);
} else
memset(dst, 0, n);
}
/*
* Process a single segment. The segment is capped to not cross page boundaries
* in both the bio and the brd backing memory.
@ -146,7 +109,8 @@ static bool brd_rw_bvec(struct brd_device *brd, struct bio *bio)
sector_t sector = bio->bi_iter.bi_sector;
u32 offset = (sector & (PAGE_SECTORS - 1)) << SECTOR_SHIFT;
blk_opf_t opf = bio->bi_opf;
void *mem;
struct page *page;
void *kaddr;
bv.bv_len = min_t(u32, bv.bv_len, PAGE_SIZE - offset);
@ -168,15 +132,19 @@ static bool brd_rw_bvec(struct brd_device *brd, struct bio *bio)
}
}
mem = bvec_kmap_local(&bv);
if (!op_is_write(opf)) {
copy_from_brd(mem, brd, sector, bv.bv_len);
flush_dcache_page(bv.bv_page);
page = brd_lookup_page(brd, sector);
kaddr = bvec_kmap_local(&bv);
if (op_is_write(opf)) {
BUG_ON(!page);
memcpy_to_page(page, offset, kaddr, bv.bv_len);
} else {
flush_dcache_page(bv.bv_page);
copy_to_brd(brd, mem, sector, bv.bv_len);
if (page)
memcpy_from_page(kaddr, page, offset, bv.bv_len);
else
memset(kaddr, 0, bv.bv_len);
}
kunmap_local(mem);
kunmap_local(kaddr);
bio_advance_iter_single(bio, &bio->bi_iter, bv.bv_len);
return true;