Re: [PATCH V3] block: drain queue before waiting for q_usage_counter becoming zero

[Ming Lei <ming.lei@redhat.com>]

On Thu, Nov 30, 2017 at 07:56:35AM +0800, Ming Lei wrote:
> Now we track legacy requests with .q_usage_counter in commit 055f6e18e08f
> ("block: Make q_usage_counter also track legacy requests"), but that
> commit never runs and drains legacy queue before waiting for this counter
> becoming zero, then IO hang is caused in the test of pulling disk during IO.
> 
> This patch fixes the issue by draining requests before waiting for
> q_usage_counter becoming zero, both Mauricio and chenxiang reported this
> issue, and observed that it can be fixed by this patch.
> 
> Link: https://marc.info/?l=linux-block&m=151192424731797&w=2
> Fixes: 055f6e18e08f("block: Make q_usage_counter also track legacy requests")
> Cc: Wen Xiong <wenxiong@us.ibm.com>
> Tested-by: "chenxiang (M)" <chenxiang66@hisilicon.com>
> Tested-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> V3:
> 	- V2 can't cover chenxiang's issue, so we have to drain queue via
> 	blk_drain_queue(), and fallback to original post(V1)

Hi Jens,

This patch fixes regression caused by 055f6e18e08f merged to v4.15-rc,
could you consider it for v4.15?

Thanks,
Ming