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Message-ID: <3c6f41ebed5ca2a669fb05ccc38e8530d0e3e220.1730286164.git.ritesh.list@gmail.com>
Date: Wed, 30 Oct 2024 21:27:41 +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 v3 4/4] ext4: Do not fallback to buffered-io for DIO atomic write
atomic writes is currently only supported for single fsblock and only
for direct-io. We should not return -ENOTBLK for atomic writes since we
want the atomic write request to either complete fully or fail
otherwise. We should not fallback to buffered-io in case of DIO atomic
write requests.
Let's also catch if this ever happens by adding some WARN_ON_ONCE before
buffered-io handling for direct-io atomic writes.
More details of the discussion [1].
[1]: https://lore.kernel.org/linux-xfs/cover.1729825985.git.ritesh.list@gmail.com/T/#m9dbecc11bed713ed0d7a486432c56b105b555f04
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
fs/ext4/file.c | 7 +++++++
fs/ext4/inode.c | 14 +++++++++-----
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 8116bd78910b..61787a37e9d4 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -599,6 +599,13 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
ssize_t err;
loff_t endbyte;
+ /*
+ * There is no support for atomic writes on buffered-io yet,
+ * we should never fallback to buffered-io for DIO atomic
+ * writes.
+ */
+ WARN_ON_ONCE(iocb->ki_flags & IOCB_ATOMIC);
+
offset = iocb->ki_pos;
err = ext4_buffered_write_iter(iocb, from);
if (err < 0)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fcdee27b9aa2..26b3c84d7f64 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3449,12 +3449,16 @@ static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
{
/*
* Check to see whether an error occurred while writing out the data to
- * the allocated blocks. If so, return the magic error code so that we
- * fallback to buffered I/O and attempt to complete the remainder of
- * the I/O. Any blocks that may have been allocated in preparation for
- * the direct I/O will be reused during buffered I/O.
+ * the allocated blocks. If so, return the magic error code for
+ * non-atomic write so that we fallback to buffered I/O and attempt to
+ * complete the remainder of the I/O.
+ * For atomic writes we will simply fail the I/O request if we coudn't
+ * write anything. For non-atomic writes, any blocks that may have been
+ * allocated in preparation for the direct I/O will be reused during
+ * buffered I/O.
*/
- if (flags & (IOMAP_WRITE | IOMAP_DIRECT) && written == 0)
+ if (!(flags & IOMAP_ATOMIC) && (flags & (IOMAP_WRITE | IOMAP_DIRECT))
+ && written == 0)
return -ENOTBLK;
return 0;
--
2.46.0
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