linux-kernel - [PATCH] xfs: Do not fallback to buffered-io for DIO atomic write

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Message-ID: <627c14b7987a3ab91d9bff31b99d86167d56f476.1729879630.git.ritesh.list@gmail.com>
Date: Fri, 25 Oct 2024 23:48:05 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-xfs@...r.kernel.org
Cc: "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>,
	Carlos Maiolino <cem@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	"Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Subject: [PATCH] xfs: 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.

Suggested-by: Darrick J. Wong <djwong@...nel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---

This should be on top of John's atomic write series [1].
[1]: https://lore.kernel.org/linux-xfs/20241019125113.369994-1-john.g.garry@oracle.com/

 fs/xfs/xfs_file.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index ca47cae5a40a..b819a9273511 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -876,6 +876,14 @@ xfs_file_write_iter(
 		ret = xfs_file_dio_write(iocb, from);
 		if (ret != -ENOTBLK)
 			return ret;
+		/*
+		 * 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)
+			return -EIO;
 	}

 	return xfs_file_buffered_write(iocb, from);
--
2.39.5