linux-ext4 - [PATCH v9 5/9] block: Make bio_iov_iter_get_pages() respect bio_required_sector

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Message-Id: <20210604210908.2105870-6-satyat@google.com>
Date:   Fri,  4 Jun 2021 21:09:04 +0000
From:   Satya Tangirala <satyat@...gle.com>
To:     "Theodore Y . Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Eric Biggers <ebiggers@...nel.org>, Chao Yu <chao@...nel.org>,
        Jens Axboe <axboe@...nel.dk>,
        "Darrick J . Wong" <darrick.wong@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-fscrypt@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-xfs@...r.kernel.org,
        linux-block@...r.kernel.org, linux-ext4@...r.kernel.org,
        Satya Tangirala <satyat@...gle.com>
Subject: [PATCH v9 5/9] block: Make bio_iov_iter_get_pages() respect bio_required_sector_alignment()

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@...gle.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