Re: mpt3sas fails to allocate budget_map and detects no devices

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

On Tue, Jan 25, 2022 at 04:29:37PM +0000, Martin Wilck wrote:
> On Wed, 2022-01-12 at 17:59 +0100, Martin Wilck wrote:
> > On Mon, 2022-01-10 at 10:59 +0800, Ming Lei wrote:
> > > 
> > > Hello Martin Wilck,
> > > 
> > > Can you test the following change and report back the result?
> > > 
> > > From 480a61a85e9669d3487ebee8db3d387df79279fc Mon Sep 17 00:00:00
> > > 2001
> > > From: Ming Lei <ming.lei@redhat.com>
> > > Date: Mon, 10 Jan 2022 10:26:59 +0800
> > > Subject: [PATCH] scsi: core: reallocate scsi device's budget map if
> > > default
> > >  queue depth is changed
> > > 
> > > Martin reported that sdev->queue_depth can often be changed in
> > > ->slave_configure(), and now we uses ->cmd_per_lun as initial queue
> > > depth for setting up sdev->budget_map. And some extreme -
> > > >cmd_per_lun
> > > or ->can_queue won't be used at default actually, if we they are
> > > used
> > > to allocate sdev->budget_map, huge memory may be consumed just
> > > because
> > > of bad ->cmd_per_lun.
> > > 
> > > Fix the issue by reallocating sdev->budget_map after -
> > > > slave_configure()
> > > returns, at that time, queue_depth should be much more reasonable.
> > > 
> > > Reported-by: Martin Wilck <martin.wilck@suse.com>
> > > Suggested-by: Martin Wilck <martin.wilck@suse.com>
> > > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > 
> > This looks good. I added a few pr_infos, and for the strange mpt3sas
> > devices I reported, I get this:
> > 
> > # first allocation with depth=7 (cmds_per_lun)
> > Jan 12 17:05:52 localhost kernel: scsi_realloc_sdev_budget_map: 7 0-
> > >0 
> >    (these numbers are: depth old_shift->new_shift)
> > Jan 12 17:05:52 localhost kernel: scsi_realloc_sdev_budget_map:
> > map_nr = 1024
> > 
> > # after slave_alloc() with depth 254
> > Jan 12 17:05:52 localhost kernel: scsi_realloc_sdev_budget_map: 254
> > 0->5
> > Jan 12 17:05:52 localhost kernel: scsi_realloc_sdev_budget_map:
> > map_nr = 32
> > 
> > So the depth changed from 7 to 254, the shift from 0 to 5, and the
> > memory size of the
> > sbitmap was reduced by a factor of 32. Nice!
> > 
> > Tested-by: Martin Wilck <mwilck@suse.com>
> > Reviewed-by: Martin Wilck <mwilck@suse.com>
> 
> So, how do we proceed with this patch?

Looks 5.18/scsi is open now, I will submit one formal patch on linux-scsi
soon.


Thanks,
Ming