locks: allow __break_lease to sleep even when break_time is 0

commit 4991a628a789dc5954e98e79476d9808812292ec upstream.

A fl->fl_break_time of 0 has a special meaning to the lease break code
that basically means "never break the lease". knfsd uses this to ensure
that leases don't disappear out from under it.

Unfortunately, the code in __break_lease can end up passing this value
to wait_event_interruptible as a timeout, which prevents it from going
to sleep at all. This causes __break_lease to spin in a tight loop and
causes soft lockups.

Fix this by ensuring that we pass a minimum value of 1 as a timeout
instead.

Cc: J. Bruce Fields <bfields@fieldses.org>
Reported-by: Terry Barnaby <terry1@beam.ltd.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/locks.c b/fs/locks.c
index fcc50ab71cc664620e686590d5e54d9bb8f77086..d4f1d89d9bc6f3d9f85bafbe2138702322e59832 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1253,11 +1253,10 @@ int __break_lease(struct inode *inode, unsigned int mode)
 
 restart:
        break_time = flock->fl_break_time;
-       if (break_time != 0) {
+       if (break_time != 0)
                break_time -= jiffies;
-               if (break_time == 0)
-                       break_time++;
-       }
+       if (break_time == 0)
+               break_time++;
        locks_insert_block(flock, new_fl);
        unlock_flocks();
        error = wait_event_interruptible_timeout(new_fl->fl_wait,