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>

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 580b2d8ce99ce04e28b68e75e92670a8915797b5..fa1290992a7fc0b9dd2c8949f4d739b8b857fcad 100644 (file)
--- 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;