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From:   Ojaswin Mujoo <ojaswin@linux.ibm.com>
To:     linux-ext4@vger.kernel.org, "Theodore Ts'o" <tytso@mit.edu>
Cc:     Ritesh Harjani <ritesh.list@gmail.com>,
        linux-kernel@vger.kernel.org,
        "Darrick J . Wong" <djwong@kernel.org>,
        linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        John Garry <john.g.garry@oracle.com>, dchinner@redhat.com
Subject: [RFC 1/7] iomap: Don't fall back to bufferred write if the write is atomic
Date:   Thu, 30 Nov 2023 19:23:10 +0530
Message-Id: <4c29ab39998ef21898e930ad78588d105f4d81a5.1701247289.git.ojaswin@linux.ibm.com>
In-Reply-To: <cover.1701247289.git.ojaswin@linux.ibm.com>
References: <cover.1701247289.git.ojaswin@linux.ibm.com>
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Currently, iomap only supports atomic writes for direct IOs and there is
no guarantees that a bufferred IO will be atomic. Hence, if the user has
explicitly requested the direct write to be atomic and there's a
failure, return -EIO instead of falling back to bufferred IO.

Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
 fs/iomap/direct-io.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 6ef25e26f1a1..d7e6c6eacbf7 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -662,7 +662,13 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 			if (ret != -EAGAIN) {
 				trace_iomap_dio_invalidate_fail(inode, iomi.pos,
 								iomi.len);
-				ret = -ENOTBLK;
+				/*
+				 * if this write was supposed to be atomic,
+				 * return the err rather than trying to fall
+				 * back to bufferred IO.
+				 */
+				if (!atomic_write)
+					ret = -ENOTBLK;
 			}
 			goto out_free_dio;
 		}
-- 
2.39.3