locks: allow __break_lease to sleep even when break_time is 0

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 makes __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: <stable@vger.kernel.org>
Cc: J. Bruce Fields <bfields@fieldses.org>
Reported-by: Terry Barnaby <terry1@beam.ltd.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

diff --git a/fs/locks.c b/fs/locks.c
index 13fc7a6d380ae6648945c8956cc53901de2d0ccc..b380f5543614802f7eb3ce68d78c9f835261e6ec 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1391,11 +1391,10 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 
 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);
        spin_unlock(&inode->i_lock);
        error = wait_event_interruptible_timeout(new_fl->fl_wait,