Re: [PATCH v2] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags

On 09/12/2021 13:52, Kashyap Desai wrote:

+ scsi mailing list

quoted

On Mon, 18 Oct 2021 17:41:23 +0800, John Garry wrote:

quoted

Since it is now possible for a tagset to share a single set of tags,
the iter function should not re-iter the tags for the count of #hw
queues in that case. Rather it should just iter once.

John - Recently we found issue of error hander thread never kicked off and
this patch fix the issue.
Without this patch, scsi error hander will not find correct host_busy
counter.

Take one simple case. There is one IO outstanding and that is getting
timedout.
Now SML wants to wake up EH thread only if, below condition met
"scsi_host_busy(shost) == shost->host_failed"

Without this patch, shared host tag enabled meagaraid_sas driver will find
host_busy = actual outstanding * nr_hw_queues.
Error handler thread will never be kicked-off.

This patch is mandatory for fixing shared host tag feature and require to be
part of stable kernel.

Do you need more data for posting to stable kernel ?

To be clear, are you saying that you see the issue which patch "blk-mq: 
Fix blk_mq_tagset_busy_iter() for shared tags" fixes before v5.16-rc?

This patch (now commit 0994c64eb415) and the commit which it is supposed 
to fix, e155b0c238b2, will only be in v5.16, so I don't see anything 
which is needed in stable.

Thanks,
John