linux-kernel - [PATCH v2 4/4] ext4: Do not fallback to buffered-io for DIO atomic write

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Message-ID: <80da397c359adaf54b87999eff6a63b331cfbcfc.1729944406.git.ritesh.list@gmail.com>
Date: Sun, 27 Oct 2024 23:47:28 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-ext4@...r.kernel.org
Cc: Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	John Garry <john.g.garry@...cle.com>,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	Dave Chinner <david@...morbit.com>,
	linux-kernel@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	"Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Subject: [PATCH v2 4/4] ext4: Do not fallback to buffered-io for DIO atomic write

iomap can return -ENOTBLK if pagecache invalidation fails.
Let's make sure if -ENOTBLK is ever returned for atomic
writes than we fail the write request (-EIO) instead of
fallback to buffered-io.

Reviewed-by: Darrick J. Wong <djwong@...nel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
 fs/ext4/file.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 8116bd78910b..22d31b4fdff3 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -576,8 +576,18 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		iomap_ops = &ext4_iomap_overwrite_ops;
 	ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops,
 			   dio_flags, NULL, 0);
-	if (ret == -ENOTBLK)
+	if (ret == -ENOTBLK) {
 		ret = 0;
+		/*
+		 * iomap can return -ENOTBLK if pagecache invalidation fails.
+		 * Let's make sure if -ENOTBLK is ever returned for atomic
+		 * writes than we fail the write request instead of fallback
+		 * to buffered-io.
+		 */
+		if (iocb->ki_flags & IOCB_ATOMIC)
+			ret = -EIO;
+	}
+
 	if (extend) {
 		/*
 		 * We always perform extending DIO write synchronously so by
--
2.46.0