Commit 53ec1abc authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Reviewed-by: default avatarYu Kuai <yukuai3@huawei.com>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20250428141014.2360063-6-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 3185444f

drivers/block/brd.c

+13 −45
Original line number Diff line number Diff line
@@ -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;