From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Marzinski Date: Tue, 30 Jun 2009 13:51:11 -0500 Subject: [Cluster-devel] GFS2: Fix panic in glock memory shrinker Message-ID: <20090630185111.GP3172@ether.msp.redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: cluster-devel@redhat.com Subject: GFS2: Fix panic in glock memory shrinker It is possible for gfs2_shrink_glock_memory() to check a glock for demotion that's in the process of being freed by gfs2_glock_put(). In this case, gfs2_shrink_glock_memory() will acquire a new reference to this glock, and then try to free the glock itself when it drops the refernce. To solve this, gfs2_shrink_glock_memory() just needs to check if the glock is in the process of being freed, and if so skip it without ever unlocking the lru_lock. Signed-off-by: Benjamin Marzinski --- fs/gfs2/glock.c | 4 ++++ 1 file changed, 4 insertions(+) Index: kernel-upstream/fs/gfs2/glock.c =================================================================== --- kernel-upstream.orig/fs/gfs2/glock.c +++ kernel-upstream/fs/gfs2/glock.c @@ -1314,6 +1314,10 @@ static int gfs2_shrink_glock_memory(int list_del_init(&gl->gl_lru); atomic_dec(&lru_count); + /* Check if glock is about to be freed */ + if (atomic_read(&gl->gl_ref) == 0) + continue; + /* Test for being demotable */ if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) { gfs2_glock_hold(gl);