linux-kernel - [PATCH 0/2] Handle update hardware queues and queue freeze more carefully

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Message-Id: <20210625101649.49296-1-dwagner@suse.de>
Date:   Fri, 25 Jun 2021 12:16:47 +0200
From:   Daniel Wagner <dwagner@...e.de>
To:     linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        James Smart <james.smart@...adcom.com>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Ming Lei <ming.lei@...hat.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Daniel Wagner <dwagner@...e.de>
Subject: [PATCH 0/2] Handle update hardware queues and queue freeze more carefully

Hi,

this is a followup on the crash I reported in

  https://lore.kernel.org/linux-block/20210608183339.70609-1-dwagner@suse.de/

By moving the hardware check up the crash was gone. Unfortuntatly, I
don't understand why this fixes the crash. The per-cpu access is
crashing but I can't see why the blk_mq_update_nr_hw_queues() is
fixing this problem.

Even though I can't explain why it fixes it, I think it makes sense to
update the hardware queue mapping bevore we recreate the IO
queues. Thus I avoided in the commit message to say it fixes
something.

Also during testing I observed the we hang indivinetly in
blk_mq_freeze_queue_wait(). Again I can't explain why we get stuck
there but given a common pattern for the nvme_wait_freeze() is to use
it with a timeout I think the timeout should be used too :)

Anyway, someone with more undertanding of the stack can explain the
problems.

Thanks,
Daniel

Daniel Wagner (2):
  nvme-fc: Update hardware queues before using them
  nvme-fc: Wait with a timeout for queue to freeze

 drivers/nvme/host/fc.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

-- 
2.29.2