linux-kernel - Re: [PATCH v3 0/6] Handle update hardware queues and queue freeze more carefully

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Message-ID: <20210730113415.wezsrvxv5cu4yz4x@beryllium.lan>
Date:   Fri, 30 Jul 2021 13:34:15 +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>,
        Ming Lei <ming.lei@...hat.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Hannes Reinecke <hare@...e.de>, Wen Xiong <wenxiong@...ibm.com>
Subject: Re: [PATCH v3 0/6] Handle update hardware queues and queue freeze
 more carefully

On Fri, Jul 30, 2021 at 11:49:07AM +0200, Daniel Wagner wrote:
> On Mon, Jul 26, 2021 at 07:27:04PM +0200, Daniel Wagner wrote:
> > FTR, I've tested the 'prior_ioq_cnt != nr_io_queues' case. In this
> > scenario the series works. Though in the case of 'prior_ioq_cnt ==
> > nr_io_queues' I see hanging I/Os.
> 
> Back on starring on this issue. So the hanging I/Os happen in this path
> after a remote port has been disabled:

It turns out, the same happens with TCP as transport. I've got two
connection configured and block traffic on the target side with
iptables rules. This is what I see

 nvme nvme16: creating 80 I/O queues.
 nvme nvme16: mapped 80/0/0 default/read/poll queues.
 nvme nvme16: new ctrl: NQN "nqn.2014-08.org.nvmexpress:NVMf:uuid:de63429f-50a4-4e03-ade6-0be27b75be77", addr 10.161.8.24:4420
 nvme nvme17: creating 80 I/O queues.
 nvme nvme17: mapped 80/0/0 default/read/poll queues.
 nvme nvme17: new ctrl: NQN "nqn.2014-08.org.nvmexpress:NVMf:uuid:de63429f-50a4-4e03-ade6-0be27b75be77", addr 10.161.8.24:4421
 nvme nvme17: starting error recovery
 nvme nvme17: failed nvme_keep_alive_end_io error=10
 nvme nvme17: Reconnecting in 10 seconds...
 nvme nvme17: failed to connect socket: -110
 nvme nvme17: Failed reconnect attempt 1
 nvme nvme17: Reconnecting in 10 seconds...
 nvme nvme17: failed to connect socket: -110
 nvme nvme17: Failed reconnect attempt 2
 nvme nvme17: Reconnecting in 10 seconds...
 nvme nvme17: creating 80 I/O queues.
 nvme nvme17: Successfully reconnected (3 attempt)

 Call Trace:
  __schedule+0x2d7/0x8f0
  schedule+0x3c/0xa0
  blk_queue_enter+0x106/0x1f0
  ? wait_woken+0x80/0x80
  submit_bio_noacct+0x116/0x4b0
  ? submit_bio+0x4b/0x1a0
  submit_bio+0x4b/0x1a0
  __blkdev_direct_IO_simple+0x20c/0x350
  ? blkdev_iopoll+0x30/0x30
  ? blkdev_direct_IO+0x4a2/0x520
  blkdev_direct_IO+0x4a2/0x520
  ? asm_sysvec_apic_timer_interrupt+0x12/0x20
  ? generic_file_read_iter+0x84/0x140
  ? __blkdev_direct_IO_simple+0x350/0x350
  generic_file_read_iter+0x84/0x140
  blkdev_read_iter+0x41/0x50
  new_sync_read+0x118/0x1a0
  vfs_read+0x15a/0x180
  ksys_pread64+0x71/0x90
  do_syscall_64+0x3c/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae

I think all transport handle the unfreezing incorrectly in the
recovering path. At least for TCP and FC I could test this. I don't have
and RDMA setup but this code looks suspiciously the same.. I think the
nvme_unfreeze() needs to be called always not just in the case where the
number of queues change.