[PATCH 3/5] xfs: drain in-flight DIO before buffered writes

[Jiale Yao <yaojiale02@163.com>]

XFS_IOLOCK_EXCL prevents new direct I/O submissions, but asynchronous
direct writes submitted while the lock was shared can remain active after
their submitting threads release the lock. A buffered write can then dirty
page cache before direct I/O completion performs post-write invalidation.

Wait for active DIO after acquiring XFS_IOLOCK_EXCL and before buffered
write checks can modify page cache. Return -EAGAIN instead of waiting for
an IOCB_NOWAIT request.

Fixes: acdda3aae146 ("xfs: use iomap_dio_rw")
Cc: stable@vger.kernel.org
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 fs/xfs/xfs_file.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 7d0c8a197575..aa7cf51b5843 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1018,6 +1018,20 @@ xfs_file_dax_write(
 	return ret;
 }
 
+STATIC int
+xfs_file_buffered_write_dio_wait(
+	struct kiocb		*iocb)
+{
+	struct inode		*inode = file_inode(iocb->ki_filp);
+
+	if (!atomic_read(&inode->i_dio_count))
+		return 0;
+	if (iocb->ki_flags & IOCB_NOWAIT)
+		return -EAGAIN;
+	inode_dio_wait(inode);
+	return 0;
+}
+
 STATIC ssize_t
 xfs_file_buffered_write(
 	struct kiocb		*iocb,
@@ -1035,6 +1049,10 @@ xfs_file_buffered_write(
 	if (ret)
 		return ret;
 
+	ret = xfs_file_buffered_write_dio_wait(iocb);
+	if (ret)
+		goto out;
+
 	ret = xfs_file_write_checks(iocb, from, &iolock, NULL);
 	if (ret)
 		goto out;
-- 
2.34.1