exfat: drain in-flight DIO before buffered writes

An asynchronous direct write can remain in flight after the inode lock is
released. If a buffered operation dirties page cache while the direct
write is still pending, the direct write's post-I/O invalidation can find
the dirty pages, report a page cache invalidation failure, and record -EIO
in the mapping error sequence. A later fsync() therefore returns -EIO.

Commit 15cdefd0c0522f9d5e12d947fa04f4c11649b699 ("ext4: drain
in-flight DIO before buffered write fallback") fixed the same race in
ext4. ExFAT does not drain in-flight DIO before a regular buffered write,
the buffered fallback after iomap_dio_rw() returns -ENOTBLK or a short
write, or the page-cache operations used to extend valid_size.

Wait for in-flight DIO before these paths can dirty page cache.

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: 867b9c96dc83 ("exfat: add iomap direct I/O support")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20260629113827.4074335-3-libaokun@linux.alibaba.com
Signed-off-by: Jiale Yao <yaojiale02@163.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions