From 53ec1abce79c986dc59e59d0c60d00088bcdf32a Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 28 Apr 2025 07:09:51 -0700 Subject: [PATCH] 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 Reviewed-by: Hannes Reinecke Reviewed-by: Yu Kuai Reviewed-by: Johannes Thumshirn Link: https://lore.kernel.org/r/20250428141014.2360063-6-hch@lst.de Signed-off-by: Jens Axboe --- drivers/block/brd.c | 58 ++++++++++----------------------------------- 1 file changed, 13 insertions(+), 45 deletions(-) diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 580b2d8ce99c..fa1290992a7f 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -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; -- 2.25.1