[PATCH 1/2] ntfs: report block device flush failures from fsync

[DaeMyung Kang]

ntfs_file_fsync() calls blkdev_issue_flush() after writeback but discards
its return value. If the device cannot flush its write cache, fsync()
reports success even though the file is not guaranteed to be durable.

Reproduce this with QEMU blkdebug failing flush_to_disk with -EIO.
On ntfs-next at 04fb910da2c8, a kretprobe recorded -EIO from
blkdev_issue_flush() while fsync() returned 0. With this change,
fsync() returns -EIO and logs the failure. The syncfs() path already
reports this error.

Fixes: 9c87959601e8 ("ntfs: update file operations")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: DaeMyung Kang <charsyam@xxxxxxxxx>
---
 fs/ntfs/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index 58afd310d57b..afc2efb4b699 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -417,14 +417,14 @@ int ntfs_file_fsync(struct file *filp, loff_t start, loff_t end,
 	err = sync_blockdev(vi->i_sb->s_bdev);
 	if (unlikely(err && !ret))
 		ret = err;
+	if (!ret)
+		ret = blkdev_issue_flush(vi->i_sb->s_bdev);
 	if (likely(!ret))
 		ntfs_debug("Done.");
 	else
 		ntfs_warning(vi->i_sb,
 				"Failed to f%ssync inode 0x%llx.  Error %u.",
 				datasync ? "data" : "", ni->mft_no, -ret);
-	if (!ret)
-		blkdev_issue_flush(vi->i_sb->s_bdev);
 	return ret;
 }
 
-- 
2.43.0