The patch titled
Subject: ocfs2/dlm: fix deadlock when dispatch assert master
has been added to the -mm tree. Its filename is
ocfs2-dlm-fix-deadlock-when-dispatch-assert-master.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ocfs2-dlm-fix-deadlock-when-dispatch-assert-master.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ocfs2-dlm-fix-deadlock-when-dispatch-assert-master.patch
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------------------------------------------------------
From: Joseph Qi <joseph.qi@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Mark Fasheh <mfasheh@xxxxxxxx>
Cc: "Junxiao Bi" <junxiao.bi@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/dlm/dlmmaster.c | 9 ++++++---
fs/ocfs2/dlm/dlmrecovery.c | 8 ++++++--
2 files changed, 12 insertions(+), 5 deletions(-)
diff -puN fs/ocfs2/dlm/dlmmaster.c~ocfs2-dlm-fix-deadlock-when-dispatch-assert-master fs/ocfs2/dlm/dlmmaster.c
--- a/fs/ocfs2/dlm/dlmmaster.c~ocfs2-dlm-fix-deadlock-when-dispatch-assert-master
+++ a/fs/ocfs2/dlm/dlmmaster.c
@@ -1439,6 +1439,7 @@ int dlm_master_request_handler(struct o2
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 dl
/* 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 -puN fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-fix-deadlock-when-dispatch-assert-master fs/ocfs2/dlm/dlmrecovery.c
--- a/fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-fix-deadlock-when-dispatch-assert-master
+++ a/fs/ocfs2/dlm/dlmrecovery.c
@@ -1694,6 +1694,7 @@ int dlm_master_requery_handler(struct o2
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 o2
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 o2
}
spin_unlock(&dlm->spinlock);
- dlm_put(dlm);
+ if (!dispatched)
+ dlm_put(dlm);
return master;
}
_
Patches currently in -mm which might be from joseph.qi@xxxxxxxxxx are
ocfs2-dlm-fix-race-between-convert-and-recovery.patch
ocfs2-dlm-fix-deadlock-when-dispatch-assert-master.patch
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