From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Whitehouse Date: Thu, 30 Jul 2009 14:45:20 +0100 Subject: [Cluster-devel] [PATCH 3/7] GFS2: Fix panic in glock memory shrinker In-Reply-To: <1248961524-30913-3-git-send-email-swhiteho@redhat.com> References: <1248961524-30913-1-git-send-email-swhiteho@redhat.com> <1248961524-30913-2-git-send-email-swhiteho@redhat.com> <1248961524-30913-3-git-send-email-swhiteho@redhat.com> Message-ID: <1248961524-30913-4-git-send-email-swhiteho@redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit From: Benjamin Marzinski 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 Acked-by: Bob Peterson Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index fdb796c..827136e 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -1314,6 +1314,10 @@ static int gfs2_shrink_glock_memory(int nr, gfp_t gfp_mask) 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); -- 1.6.2.2