From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bob Peterson Date: Mon, 16 Nov 2015 13:13:07 -0500 (EST) Subject: [Cluster-devel] [PATCH v2] GFS2: Use rht_for_each_entry_rcu in glock_hash_walk In-Reply-To: <1447417018-1856-1-git-send-email-anprice@redhat.com> References: <5644F8D7.4000808@redhat.com> <1447417018-1856-1-git-send-email-anprice@redhat.com> Message-ID: <16614614.12201324.1447697587132.JavaMail.zimbra@redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit ----- Original Message ----- > This lockdep splat was being triggered on umount: > > [55715.973122] =============================== > [55715.980169] [ INFO: suspicious RCU usage. ] > [55715.981021] 4.3.0-11553-g8d3de01-dirty #15 Tainted: G W > [55715.982353] ------------------------------- > [55715.983301] fs/gfs2/glock.c:1427 suspicious rcu_dereference_protected() > usage! > > The code it refers to is the rht_for_each_entry_safe usage in > glock_hash_walk. The condition that triggers the warning is > lockdep_rht_bucket_is_held(tbl, hash) which is checked in the > __rcu_dereference_protected macro. > > The rhashtable buckets are not changed in glock_hash_walk so it's safe > to rely on the rcu protection. Replace the rht_for_each_entry_safe() > usage with rht_for_each_entry_rcu(), which doesn't care whether the > bucket lock is held if the rcu read lock is held. > > Signed-off-by: Andrew Price > --- > fs/gfs2/glock.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c > index 32e7471..430326e 100644 > --- a/fs/gfs2/glock.c > +++ b/fs/gfs2/glock.c > @@ -1417,14 +1417,14 @@ static struct shrinker glock_shrinker = { > static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd > *sdp) > { > struct gfs2_glock *gl; > - struct rhash_head *pos, *next; > + struct rhash_head *pos; > const struct bucket_table *tbl; > int i; > > rcu_read_lock(); > tbl = rht_dereference_rcu(gl_hash_table.tbl, &gl_hash_table); > for (i = 0; i < tbl->size; i++) { > - rht_for_each_entry_safe(gl, pos, next, tbl, i, gl_node) { > + rht_for_each_entry_rcu(gl, pos, tbl, i, gl_node) { > if ((gl->gl_name.ln_sbd == sdp) && > lockref_get_not_dead(&gl->gl_lockref)) > examiner(gl); > -- > 2.4.3 > > Hi, Thanks. This is now applied to the for-next branch of the linux-gfs2 tree: https://git.kernel.org/cgit/linux/kernel/git/gfs2/linux-gfs2.git/commit/fs/gfs2?h=for-next&id=3dd1dd8c696bdb7c8dcc9456cb23558ad1b336b8 Regards, Bob Peterson Red Hat File Systems