Sagi Grimberg 657f1975e9 nvme: fix deadlock caused by ANA update wrong locking ... The deadlock combines 4 flows in parallel: - ns scanning (triggered from reconnect) - request timeout - ANA update (triggered from reconnect) - I/O coming into the mpath device (1) ns scanning triggers disk revalidation -> update disk info -> freeze queue -> but blocked, due to (2) (2) timeout handler reference the g_usage_counter - > but blocks in the transport .timeout() handler, due to (3) (3) the transport timeout handler (indirectly) calls nvme_stop_queue() -> which takes the (down_read) namespaces_rwsem - > but blocks, due to (4) (4) ANA update takes the (down_write) namespaces_rwsem -> calls nvme_mpath_set_live() -> which synchronize the ns_head srcu (see commit 504db087aa) -> but blocks, due to (5) (5) I/O came into nvme_mpath_make_request -> took srcu_read_lock -> direct_make_request > blk_queue_enter -> but blocked, due to (1) ==> the request queue is under freeze -> deadlock. The fix is making ANA update take a read lock as the namespaces list is not manipulated, it is just the ns and ns->head that are being updated (which is protected with the ns->head lock). Fixes: 0d0b660f21 ("nvme: add ANA support") Signed-off-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Christoph Hellwig <hch@lst.de>		2020-04-04 09:07:03 +02:00
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host	nvme: fix deadlock caused by ANA update wrong locking	2020-04-04 09:07:03 +02:00
target	nvmet-rdma: fix bonding failover possible NULL deref	2020-04-04 09:06:55 +02:00
Kconfig	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00