tree 6b4331c36b3ccee82d22e62fc133f07ad060e11c
parent 79272b3562bb44ce7dc720cd13136f5a4a53c618
author Steven Whitehouse <swhiteho@redhat.com> 1403531012 +0100
committer Steven Whitehouse <swhiteho@redhat.com> 1405678371 +0100

GFS2: Fix race in glock lru glock disposal

We must not leave items on the LRU list with GLF_LOCK set, since
they can be removed if the glock is brought back into use, which
may then potentially result in a hang, waiting for GLF_LOCK to
clear.

It doesn't happen very often, since it requires a glock that has
not been used for a long time to be brought back into use at the
same moment that the shrinker is part way through disposing of
glocks.

The fix is to set GLF_LOCK at a later time, when we already know
that the other locks can be obtained. Also, we now only release
the lru_lock in case a resched is needed, rather than on every
iteration.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>