gfs2: fix flock panic issue

BugLink: https://bugs.launchpad.net/bugs/1878232

commit a93a9983 upstream.

Commit 4f656367 ("Move locks API users to locks_lock_inode_wait()")
moved flock/posix lock identify code to locks_lock_inode_wait(), but
missed to set fl_flags to FL_FLOCK which will cause kernel panic in
locks_lock_inode_wait().

Fixes: 4f656367 ("Move locks API users to locks_lock_inode_wait()")
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/gfs2/file.c

@@ -1035,7 +1035,10 @@ static int do_flock(struct file *file, int cmd, struct file_lock *fl)
 		if (fl_gh->gh_state == state)
 			goto out;
 		locks_lock_file_wait(file,
-				     &(struct file_lock){.fl_type = F_UNLCK});
+				     &(struct file_lock) {
+					     .fl_type = F_UNLCK,
+					     .fl_flags = FL_FLOCK
+				     });
 		gfs2_glock_dq(fl_gh);
 		gfs2_holder_reinit(state, flags, fl_gh);
 	} else {