locks: eliminate BUG() call when there's an unexpected lock on file close

A leftover lock on the list is surely a sign of a problem of some sort,
but it's not necessarily a reason to panic the box. Instead, just log a
warning with some info about the lock, and then delete it like we would
any other lock.

In the event that the filesystem declares a ->lock f_op, we may end up
leaking something, but that's generally preferable to an immediate
panic.

Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

1 files changed, 18 insertions, 6 deletions

diff --git a/fs/locks.c b/fs/locks.c
index 6084f5a32e9c..dd309333afc9 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2281,16 +2281,28 @@ void locks_remove_flock(struct file *filp)
 
         while ((fl = *before) != NULL) {
                 if (fl->fl_file == filp) {
-                        if (IS_FLOCK(fl)) {
-                                locks_delete_lock(before);
-                                continue;
-                        }
                         if (IS_LEASE(fl)) {
                                 lease_modify(before, F_UNLCK);
                                 continue;
                         }
-                        /* What? */
-                        BUG();
+
+                        /*
+                         * There's a leftover lock on the list of a type that
+                         * we didn't expect to see. Most likely a classic
+                         * POSIX lock that ended up not getting released
+                         * properly, or that raced onto the list somehow. Log
+                         * some info about it and then just remove it from
+                         * the list.
+                         */
+                        WARN(!IS_FLOCK(fl),
+                                "leftover lock: dev=%u:%u ino=%lu type=%hhd flags=0x%x start=%lld end=%lld\n",
+                                MAJOR(inode->i_sb->s_dev),
+                                MINOR(inode->i_sb->s_dev), inode->i_ino,
+                                fl->fl_type, fl->fl_flags,
+                                fl->fl_start, fl->fl_end);
+
+                        locks_delete_lock(before);
+                        continue;
                 }
                 before = &fl->fl_next;
         }