[PATCH 2/2] ext4: Fix fsync(2) for nojournal mode

[Jan Kara <jack@suse.cz>]

When inode metadata is changed, we sometimes just call
ext4_mark_inode_dirty() to track modified metadata. This copies inode
metadata into block buffer which is enough when we are journalling
metadata. However when we are running in nojournal mode we currently
fail to write the dirtied inode buffer during fsync(2) because the inode
is not marked as dirty. Use explicit ext4_write_inode() call to make
sure the inode table buffer is written to the disk. This is a band aid
solution but proper solution requires a much larger rewrite including
changes in metadata bh tracking infrastructure.

Reported-by: Free Ekanayaka <free.ekanayaka@gmail.com>
Link: https://lore.kernel.org/all/87il8nhxdm.fsf@x1.mail-host-address-is-not-set/
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/fsync.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index e476c6de3074..bd8f230fa507 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -83,11 +83,23 @@ static int ext4_fsync_nojournal(struct file *file, loff_t start, loff_t end,
 				int datasync, bool *needs_barrier)
 {
 	struct inode *inode = file->f_inode;
+	struct writeback_control wbc = {
+		.sync_mode = WB_SYNC_ALL,
+		.nr_to_write = 0,
+	};
 	int ret;
 
 	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
-	if (!ret)
-		ret = ext4_sync_parent(inode);
+	if (ret)
+		return ret;
+
+	/* Force writeout of inode table buffer to disk */
+	ret = ext4_write_inode(inode, &wbc);
+	if (ret)
+		return ret;
+
+	ret = ext4_sync_parent(inode);
+
 	if (test_opt(inode->i_sb, BARRIER))
 		*needs_barrier = true;
 
-- 
2.51.0