block: take destination bvec offsets into account in bio_copy_data_iter

Appartly bcache can copy into bios that do not just contain fresh
pages but can have offsets into the bio_vecs.  Restore support for tht
in bio_copy_data_iter.

Fixes: f8b679a070c5 ("block: rewrite bio_copy_data_iter to use bvec_kmap_local and memcpy_to_bvec")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220524143919.1155501-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index a3893d8..8a1b3d6 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1366,10 +1366,12 @@ void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
                struct bio_vec src_bv = bio_iter_iovec(src, *src_iter);
                struct bio_vec dst_bv = bio_iter_iovec(dst, *dst_iter);
                unsigned int bytes = min(src_bv.bv_len, dst_bv.bv_len);
-               void *src_buf;
+               void *src_buf = bvec_kmap_local(&src_bv);
+               void *dst_buf = bvec_kmap_local(&dst_bv);
 
-               src_buf = bvec_kmap_local(&src_bv);
-               memcpy_to_bvec(&dst_bv, src_buf);
+               memcpy(dst_buf, src_buf, bytes);
+
+               kunmap_local(dst_buf);
                kunmap_local(src_buf);
 
                bio_advance_iter_single(src, src_iter, bytes);