Re: [PATCH] blk-mq: Fix several SCSI request queue lockups

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

On Tue, Dec 05, 2017 at 12:29:59AM +0000, Bart Van Assche wrote:
> On Tue, 2017-12-05 at 08:20 +0800, Ming Lei wrote:
> > Also it is a bit odd to see request in hctx->dispatch now, and it can only
> > happen now when scsi_target_queue_ready() returns false, so I guess you apply
> > some change on target->can_queue(such as setting it as 1 in srp/ib code
> > manually)?
> 
> Yes, but that had already been mentioned. From the e-mail at the start of
> this e-mail thread: "Change the SRP initiator such that SCSI target queue
> depth is limited to 1." The changes I made in the SRP initiator are the same
> as those described in the following message from about one month ago:
> https://www.spinics.net/lists/linux-scsi/msg114720.html.

OK, got it.

Then no reason to revert commit(0df21c86bdbf scsi: implement .get_budget an
.put_budget for blk-mq) for one issue which may never happen in reality since
this reproducer need out-of-tree patch.

I don't mean it isn't a issue, but I don't think it has top priority
for reverting commit 0df21c86bdbf. Especially there isn't proof shown
that 0df21c86bdbf causes this issue since this commit won't change run
queue for requests in hctx->dispatch_list.

I's like to take a look if someone'd like to cooperate, such as
providing kernel log, test debug patch, and kind of things. Or when
I get this hardware to reproduce.

--
Ming