[PATCH v9 5/9] block: Make bio_iov_iter_get_pages() respect bio_required_sector_alignment()

Satya Tangirala
2021-06-04T21:09:22Z

Previously, bio_iov_iter_get_pages() wasn't used with bios that could have
an encryption context. However, direct I/O support using blk-crypto
introduces this possibility, so this function must now respect
bio_required_sector_alignment() (otherwise, xfstests like generic/465 with
ext4 will fail).

Signed-off-by: Satya Tangirala <satyat@google.com>
---
block/bio.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 32f75f31bb5c..99c510f706e2 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1099,7 +1099,8 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
* The function tries, but does not guarantee, to pin as many pages as
* fit into the bio, or are requested in @iter, whatever is smaller. If
* MM encounters an error pinning the requested pages, it stops. Error
- * is returned only if 0 pages could be pinned.
+ * is returned only if 0 pages could be pinned. It also ensures that the number
+ * of sectors added to the bio is aligned to bio_required_sector_alignment().
*
* It's intended for direct IO, so doesn't do PSI tracking, the caller is
* responsible for setting BIO_WORKINGSET if necessary.
@@ -1107,6 +1108,7 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
{
int ret = 0;
+ unsigned int aligned_sectors;

if (iov_iter_is_bvec(iter)) {
if (bio_op(bio) == REQ_OP_ZONE_APPEND)
@@ -1121,6 +1123,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
ret = __bio_iov_iter_get_pages(bio, iter);
} while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));

+ /*
+ * Ensure that number of sectors in bio is aligned to
+ * bio_required_sector_align()
+ */
+ aligned_sectors = round_down(bio_sectors(bio),
+ bio_required_sector_alignment(bio));
+ iov_iter_revert(iter, (bio_sectors(bio) - aligned_sectors) << SECTOR_SHIFT);
+ bio_truncate(bio, aligned_sectors << SECTOR_SHIFT);
+
/* don't account direct I/O as memory stall */
bio_clear_flag(bio, BIO_WORKINGSET);
return bio->bi_vcnt ? 0 : ret;
--
2.32.0.rc1.229.g3e70b5a671-goog