[PATCH 2/3] block: simplify minsize alignment in bio_iov_iter_bounce_write

[Christoph Hellwig <hch@lst.de>]

Don't allow partial copies to create unaligned length, which the file
systems can't handle, and remove thee need for the separate
bio_iov_iter_align_down() pass.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 23f739d5321d..7f707ecf328e 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1399,7 +1399,12 @@ static int bio_iov_iter_bounce_write(struct bio *bio, struct iov_iter *iter,
 			 * bytes as @this_len is queued but only advanced
 			 * less than that.
 			 * Need to compensate that for the revert.
+			 *
+			 * Round down the amount copied to the minimum size /
+			 * aligned required by the file system so that we don't
+			 * create unaligned bios.
 			 */
+			copied = rounddown(copied, minsize);
 			iov_iter_revert(iter, bio->bi_iter.bi_size - this_len +
 					copied);
 			bio_free_folios(bio);
@@ -1410,7 +1415,7 @@ static int bio_iov_iter_bounce_write(struct bio *bio, struct iov_iter *iter,
 
 	if (!bio->bi_iter.bi_size)
 		return -ENOMEM;
-	return bio_iov_iter_align_down(bio, iter, minsize - 1);
+	return 0;
 }
 
 static int bio_iov_iter_bounce_read(struct bio *bio, struct iov_iter *iter,
-- 
2.53.0