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Xue jiufei authored
We found there is a conversion deadlock when the owner of lockres happened to crash before send DLM_PROXY_AST_MSG for a downconverting lock. The situation is as follows: Node1 Node2 Node3 the owner of lockresA lock_1 granted at EX mode and call ocfs2_cluster_unlock to decrease ex_holders. converting lock_3 from NL to EX send DLM_PROXY_AST_MSG to Node1, asking Node 1 to downconvert. receiving DLM_PROXY_AST_MSG, thread ocfs2dc send DLM_CONVERT_LOCK_MSG to Node2 to downconvert lock_1(EX->NL). lock_1 can be granted and put it into pending_asts list, return DLM_NORMAL. then something happened and Node2 crashed. received DLM_NORMAL, waiting for DLM_PROXY_AST_MSG. selected as the recovery master, receving migrate lock from Node1, queue lock_1 to the tail of converting list. After dlm recovery, converting list in the master of lockresA(Node3) will be: converting list head <-> lock_3(NL->EX) <->lock_1(EX<->NL). Requested mode of lock_3 is not compatible with the granted mode of lock_1, so it can not be granted. and lock_1 can not downconvert because covnerting queue is strictly FIFO. So a deadlock is created. We think function dlm_process_recovery_data() should queue_ast for lock_1 or alter the order of lock_1 and lock_3, so dlm_thread can process lock_1 first. And if there are multiple downconverting locks, they must convert form PR to NL, so no need to sort them. Signed-off-by:
joyce.xue <xuejiufei@huawei.com> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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