From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bob Peterson Date: Tue, 30 Jun 2009 15:02:32 -0400 (EDT) Subject: [Cluster-devel] GFS2: Fix panic in glock memory shrinker In-Reply-To: <20090630185111.GP3172@ether.msp.redhat.com> Message-ID: <914250311.656991246388552553.JavaMail.root@zmail06.collab.prod.int.phx2.redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit ----- "Benjamin Marzinski" wrote: | To: cluster-devel at 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); Hi, ACKed by Bob Peterson Regards, Bob Peterson Red Hat File Systems