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ext2: drain in-flight DIO before buffered write fallback

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An asynchronous direct write can remain in flight after the inode lock is
released.  If another direct write falls back to buffered I/O while the
first write is still pending, generic_perform_write() can dirty pages
before the first write completes its post-I/O page cache invalidation.
The invalidation then finds dirty pages, reports a page cache invalidation
failure, and records -EIO in the mapping error sequence.  A later fsync()
therefore returns -EIO.

Commit 15cdefd0c0 ("ext4: drain
in-flight DIO before buffered write fallback") fixed the same race in
ext4.  Ext2 has an equivalent fallback after iomap_dio_rw() returns
-ENOTBLK or a short write, but does not drain other in-flight DIO before
dirtying the page cache.

Wait for in-flight DIO before calling generic_perform_write() in the
fallback path.

A reproducer using concurrent AIO direct writes and buffered fallback
triggered the following warning and made a subsequent fsync() return
-EIO:

  Page cache invalidation failure on direct I/O.  Possible data corruption
  due to collision with buffered I/O!

Fixes: fb5de4358e ("ext2: Move direct-io to use iomap")
Link: https://lore.kernel.org/r/20260629113827.4074335-3-libaokun@linux.alibaba.com
Signed-off-by: Jiale Yao <yaojiale02@163.com>
Link: https://patch.msgid.link/20260924105125.577714-2-yaojiale02@163.com
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jiale Yao 2026-09-24 18:51:23 +08:00 committed by Jan Kara
parent 6e69419ca6
commit 1e2ef9f221
1 changed files with 7 additions and 0 deletions
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7
fs/ext2/file.c
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@ -135,6 +135,13 @@ static ssize_t ext2_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
int ret2;
iocb->ki_flags &= ~IOCB_DIRECT;
/*
* Prevent concurrent direct I/O and buffered I/O to the same file
* range. Wait for in-flight DIO to finish before dirtying pages.
*/
inode_dio_wait(inode);
pos = iocb->ki_pos;
status = generic_perform_write(iocb, from);
if (unlikely(status < 0)) {