Commit 012572d4 authored by Joseph Qi's avatar Joseph Qi Committed by Linus Torvalds

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: default avatarJoseph 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7a07b503
......@@ -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 @@ int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data,
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 */
......
......@@ -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;
}
......
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