[PATCH 4/5] xfs: drain in-flight DIO before zoned buffered writes

[Jiale Yao <yaojiale02@163.com>]

Buffered writes to zoned realtime files hold XFS_IOLOCK_EXCL, but direct
I/O submitted earlier while holding the lock shared can still be active.
The buffered write can dirty page cache before the asynchronous direct
write completes its post-I/O invalidation, causing an invalidation failure
and a mapping error.

Use the buffered-write DIO drain after acquiring XFS_IOLOCK_EXCL and
before the zoned write checks can touch page cache. Preserve NOWAIT
semantics by returning -EAGAIN when a wait would be needed.

Fixes: 2e2383405824 ("xfs: implement direct writes to zoned RT devices")
Cc: stable@vger.kernel.org
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 fs/xfs/xfs_file.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index aa7cf51b5843..96a11af8e71a 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1121,6 +1121,10 @@ xfs_file_buffered_write_zoned(
 	if (ret)
 		goto out_unreserve;
 
+	ret = xfs_file_buffered_write_dio_wait(iocb);
+	if (ret)
+		goto out_unlock;
+
 	ret = xfs_file_write_checks(iocb, from, &iolock, &ac);
 	if (ret)
 		goto out_unlock;
-- 
2.34.1