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<pre>We found that a BUG in the dlm_proxy_ast_handler function causes the machine panic.
The core information that causes the BUG in the dlm_proxy_ast_handler function is as follows.
[ 699.795843] kernel BUG at /usr/src/linux-4.18/fs/ocfs2/dlm/dlmast.c:427!
[ 699.801963] Workqueue: o2net o2net_rx_until_empty [ocfs2_nodemanager]
[ 699.803275] RIP: 0010:dlm_proxy_ast_handler+0x738/0x740 [ocfs2_dlm]
[ 699.808506] RSP: 0018:ffffba64c6f2fd38 EFLAGS: 00010246
[ 699.809456] RAX: ffff9f34a9b39148 RBX: ffff9f30b7af4000 RCX: ffff9f34a9b39148
[ 699.810698] RDX: 000000000000019e RSI: ffffffffc091a930 RDI: ffffba64c6f2fd80
[ 699.811927] RBP: ffff9f2cb7aa3000 R08: ffff9f2cb7b99400 R09: 000000000000001f
[ 699.813457] R10: ffff9f34a9249200 R11: ffff9f34af23aa00 R12: 0000000040000000
[ 699.814719] R13: ffff9f34a9249210 R14: 0000000000000002 R15: ffff9f34af23aa28
[ 699.815984] FS: 0000000000000000(0000) GS:ffff9f32b7c00000(0000) knlGS:0000000000000000
[ 699.817417] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 699.818825] CR2: 00007fd772f5a140 CR3: 000000005b00a001 CR4: 00000000001606e0
[ 699.820123] Call Trace:
[ 699.820658] o2net_rx_until_empty+0x94b/0xcc0 [ocfs2_nodemanager]
[ 699.821848] process_one_work+0x171/0x370
[ 699.822595] worker_thread+0x49/0x3f0
[ 699.823301] kthread+0xf8/0x130
[ 699.823972] ? max_active_store+0x80/0x80
[ 699.824881] ? kthread_bind+0x10/0x10
[ 699.825589] ret_from_fork+0x35/0x40
Here is the situation: At the beginning, Node1 is the master
of the lock resource and has NL lock, Node2 has PR lock,
Node3 has PR lock, Node4 has NL lock.
Node1 Node2 Node3 Node4
convert lock_2 from
PR to EX.
the mode of lock_3 is
PR, which blocks the
conversion request of
Node2. move lock_2 to
conversion list.
convert lock_3 from
PR to EX.
move lock_3 to conversion
list. send BAST to Node3.
receive BAST from Node1.
downconvert thread execute
canceling convert operation.
Node1 dies because
the host is powered down.
in dlmunlock_common function,
the downconvert thread set
cancel_pending. at the same
time, Node3 realized that
Node 1 is dead, so move lock_3
back to granted list in
dlm_move_lockres_to_recovery_list
function and remove Node 1 from
the domain_map in
__dlm_hb_node_down function.
then downconvert thread failed
to send the lock cancellation
request to Node1 and return
DLM_NORMAL from
dlm_send_remote_unlock_request
function.
become recovery master.
during the recovery
process, send
lock_2 that is
converting form
PR to EX to Node4.
during the recovery process,
send lock_3 in the granted list and
cantain the DLM_LKSB_GET_LVB
flag to Node4. Then downconvert thread
delete DLM_LKSB_GET_LVB flag in
dlmunlock_common function.
Node4 finish recovery.
the mode of lock_3 is
PR, which blocks the
conversion request of
Node2, so send BAST
to Node3.
receive BAST from Node4.
convert lock_3 from PR to NL.
change the mode of lock_3
from PR to NL and send
message to Node3.
receive message from
Node4. The message contain
LKM_GET_LVB flag, but the
lock->lksb->flags does not
contain DLM_LKSB_GET_LVB,
BUG_ON in dlm_proxy_ast_handler
function.
Function dlm_move_lockres_to_recovery_list should clean DLM_LKSB_GET_LVB
and DLM_LKSB_PUT_LVB when the cancel_pending is set. The reasons for
clearing the these flags are as follows. First, The owner of the lock resource
may have died, the lock has been moved to the grant queue, the purpose of the lock cancellation
has been reached, and the LVB flag should be cleared. Second, solve this panic problem.
Signed-off-by: Jian Wang <a class="moz-txt-link-rfc2396E" href="mailto:wangjian161@huawei.com"><wangjian161@huawei.com></a>
Reviewed-by: Yiwen Jiang <a class="moz-txt-link-rfc2396E" href="mailto:jiangyiwen@huawei.com"><jiangyiwen@huawei.com></a>
---
fs/ocfs2/dlm/dlmunlock.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/ocfs2/dlm/dlmunlock.c b/fs/ocfs2/dlm/dlmunlock.c
index 63d701c..6e04fc7 100644
--- a/fs/ocfs2/dlm/dlmunlock.c
+++ b/fs/ocfs2/dlm/dlmunlock.c
@@ -277,6 +277,7 @@ void dlm_commit_pending_cancel(struct dlm_lock_resource *res,
{
list_move_tail(&lock->list, &res->granted);
lock->ml.convert_type = LKM_IVMODE;
+ lock->lksb->flags &= ~(DLM_LKSB_GET_LVB|DLM_LKSB_PUT_LVB);
}
--
1.8.3.1
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