ocfs2/dlm: fix deadlock when dispatch assert master

The order of the following three spinlocks should be:
dlm_domain_lock < dlm_ctxt->spinlock < dlm_lock_resource->spinlock

But dlm_dispatch_assert_master() is called while holding
dlm_ctxt->spinlock and dlm_lock_resource->spinlock, and then it calls
dlm_grab() which will take dlm_domain_lock.

Once another thread (for example, dlm_query_join_handler) has already
taken dlm_domain_lock, and tries to take dlm_ctxt->spinlock deadlock
happens.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: "Junxiao Bi" <junxiao.bi@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 46b8b2b..ee5aa4d 100644 (file)
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -1439,6 +1439,7 @@ int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data,
        int found, ret;
        int set_maybe;
        int dispatch_assert = 0;
+       int dispatched = 0;
 
        if (!dlm_grab(dlm))
                return DLM_MASTER_RESP_NO;
@@ -1658,15 +1659,18 @@ send_response:
                        mlog(ML_ERROR, "failed to dispatch assert master work\n");
                        response = DLM_MASTER_RESP_ERROR;
                        dlm_lockres_put(res);
-               } else
+               } else {
+                       dispatched = 1;
                        __dlm_lockres_grab_inflight_worker(dlm, res);
+               }
                spin_unlock(&res->spinlock);
        } else {
                if (res)
                        dlm_lockres_put(res);
        }
 
-       dlm_put(dlm);
+       if (!dispatched)
+               dlm_put(dlm);
        return response;
 }
 
@@ -2090,7 +2094,6 @@ int dlm_dispatch_assert_master(struct dlm_ctxt *dlm,
 
 
        /* queue up work for dlm_assert_master_worker */
-       dlm_grab(dlm);  /* get an extra ref for the work item */
        dlm_init_work_item(dlm, item, dlm_assert_master_worker, NULL);
        item->u.am.lockres = res; /* already have a ref */
        /* can optionally ignore node numbers higher than this node */

diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index ce12e0b..3d90ad7 100644 (file)
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -1694,6 +1694,7 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data,
        unsigned int hash;
        int master = DLM_LOCK_RES_OWNER_UNKNOWN;
        u32 flags = DLM_ASSERT_MASTER_REQUERY;
+       int dispatched = 0;
 
        if (!dlm_grab(dlm)) {
                /* since the domain has gone away on this
@@ -1719,8 +1720,10 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data,
                                dlm_put(dlm);
                                /* sender will take care of this and retry */
                                return ret;
-                       } else
+                       } else {
+                               dispatched = 1;
                                __dlm_lockres_grab_inflight_worker(dlm, res);
+                       }
                        spin_unlock(&res->spinlock);
                } else {
                        /* put.. incase we are not the master */
@@ -1730,7 +1733,8 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data,
        }
        spin_unlock(&dlm->spinlock);
 
-       dlm_put(dlm);
+       if (!dispatched)
+               dlm_put(dlm);
        return master;
 }