ext4: fix fsync for non-directories

Commit e360c6e ("ext4: Drop special handling of journalled data
from ext4_sync_file()") simplified ext4_sync_file() by dropping special
handling of journalled data mode as it was not needed anymore. However
that branch was also used for directories and symlinks and since the
fastcommit code does not track metadata changes to non-regular files, the
change has caused e.g. fsync(2) on directories to not commit transaction
as it should. Fix the problem by adding handling for non-regular files.

Fixes: e360c6e ("ext4: Drop special handling of journalled data from ext4_sync_file()")
Reported-by: Eric Whitney <enwlinux@gmail.com>
Link: https://lore.kernel.org/all/ZFqO3xVnmhL7zv1x@debian-BULLSEYE-live-builder-AMD64
Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Eric Whitney <enwlinux@gmail.com>
Link: https://lore.kernel.org/r/20230524104453.8734-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/fsync.c

@@ -108,6 +108,13 @@ static int ext4_fsync_journal(struct inode *inode, bool datasync,
 	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 	tid_t commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 
+	/*
+	 * Fastcommit does not really support fsync on directories or other
+	 * special files. Force a full commit.
+	 */
+	if (!S_ISREG(inode->i_mode))
+		return ext4_force_commit(inode->i_sb);
+
 	if (journal->j_flags & JBD2_BARRIER &&
 	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 		*needs_barrier = true;