From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joseph Qi Date: Wed, 29 Oct 2014 16:04:20 +0800 Subject: [Ocfs2-devel] [PATCH 1/1] o2dlm: fix a race between purge and master query In-Reply-To: <1414535056-30193-1-git-send-email-srinivas.eeda@oracle.com> References: <1414535056-30193-1-git-send-email-srinivas.eeda@oracle.com> Message-ID: <54509F84.4040909@huawei.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com We tested this patch and it works well. Thanks. Tested-by: Joseph Qi On 2014/10/29 6:24, Srinivas Eeda wrote: > Node A sends master query request to node B which is the master. At this time > lockres happens to be on purgelist. dlm_master_request_handler gets the dlm > spinlock, finds the resource and releases the dlm spin lock. Right at this > dlm_thread on this node could purge the lockres. dlm_master_request_handler > can then acquire lockres spinlock and reply to Node A that node B is the > master even though lockres on node B is purged. > > The above scenario will now make node A falsely think node B is the master > which is inconsistent. Further if another node C tries to master the same > resource, every node will respond they are not the master. Node C then masters > the resource and sends assert master to all nodes. This will now make node A > crash with the following message. > > dlm_assert_master_handler:1831 ERROR: DIE! Mastery assert from 9, but current > owner is 10! > > Signed-off-by: Srinivas Eeda > --- > fs/ocfs2/dlm/dlmmaster.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c > index 215e41a..3689b35 100644 > --- a/fs/ocfs2/dlm/dlmmaster.c > +++ b/fs/ocfs2/dlm/dlmmaster.c > @@ -1460,6 +1460,18 @@ way_up_top: > > /* take care of the easy cases up front */ > spin_lock(&res->spinlock); > + > + /* > + * Right after dlm spinlock was released, dlm_thread could have > + * purged the lockres. Check if lockres got unhashed. If so > + * start over. > + */ > + if (hlist_unhashed(&res->hash_node)) { > + spin_unlock(&res->spinlock); > + dlm_lockres_put(res); > + goto way_up_top; > + } > + > if (res->state & (DLM_LOCK_RES_RECOVERING| > DLM_LOCK_RES_MIGRATING)) { > spin_unlock(&res->spinlock); >