[PATCH v1 0/2] blk-mq: fix oops caused by CPU hotplug

[Ming Lei]

Hi Guys,

Dongsu Park reported[1] that kernel oops can be triggered easily by
CPU plug when there is pending I/O on virtio-scsi.

Turns out two problems exist in blk-mq core code and both can trigger
oops by CPU plug:
        - timeout handling vs CPU hotplug, especially unmapped hw queue tags
        is still touched by timeout handler
        - in case of shared tags, there is one bug about setting and checking
        hctx->tags during CPU hotplug

The two patches fix the two problem, and Dongsu has verified that
the oops is fixed with the two patches too.

[1], http://marc.info/?t=142926389200008&r=1&w=2

V1:
	- update comment
	- moving tags allocation in blk_mq_map_swqueue() because
	unmapped hw queue can be remapped after CPU topo is changed

 block/blk-mq.c |   50 ++++++++++++++++++++++++++------------------------
 1 file changed, 26 insertions(+), 24 deletions(-)


Thanks,
Ming Lei

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