RE: [PATCH 04/11] megaraid_sas : Firmware crash dump feature support

From: "Elliott, Robert (Server Storage)" <Elliott@hp.com>
To: Sumit Saxena <sumit.saxena@avagotech.com>,
	Tomas Henzl <thenzl@redhat.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Cc: "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"hch@infradead.org" <hch@infradead.org>,
	"jbottomley@parallels.com" <jbottomley@parallels.com>,
	Kashyap Desai <kashyap.desai@avagotech.com>,
	"aradford@gmail.com" <aradford@gmail.com>,
	Michal Schmidt <mschmidt@redhat.com>,
	"amirv@mellanox.com" <amirv@mellanox.com>,
	"vgoyal@redhat.com" <vgoyal@redhat.com>,
	"Jens Axboe <axboe@kernel.dk> (axboe@kernel.dk)"
	<axboe@kernel.dk>,
	"scameron@beardog.cce.hp.com" <scameron@beardog.cce.hp.com>
Subject: RE: [PATCH 04/11] megaraid_sas : Firmware crash dump feature support
Date: Wed, 10 Sep 2014 15:06:48 +0000	[thread overview]
Message-ID: <94D0CD8314A33A4D9D801C0FE68B402958C70F51@G9W0745.americas.hpqcorp.net> (raw)
In-Reply-To: <55ba5d7cdee7dbcce18dc1a2bbbefc03@mail.gmail.com>

> From: linux-scsi-owner@vger.kernel.org [mailto:linux-scsi-
> owner@vger.kernel.org] On Behalf Of Sumit Saxena
> 
> >From: Tomas Henzl [mailto:thenzl@redhat.com]
> >
> >With several controllers in a system this may take a lot memory,
> > could you also in case when a kdump kernel is running lower it,
> > by not using this feature?
> >
> Agreed, we will disable this feature for kdump kernel by adding
> "reset_devices" global varaiable.
> That check is required for only one place, throughout the code, this
> feature will remain disabled.  Code snippet for the same-
> 
>         instance->crash_dump_drv_support = (!reset_devices) &&
> crashdump_enable &&
>                                 instance->crash_dump_fw_support &&
>                                 instance->crash_dump_buf);
>         if(instance->crash_dump_drv_support) {
>                 printk(KERN_INFO "megaraid_sas: FW Crash dump is
> supported\n");
>                 megasas_set_crash_dump_params(instance,
> MR_CRASH_BUF_TURN_OFF);
> 
>         } else {
> ..
>         }

Network drivers have been running into similar problems.

There's a new patch from Amir coming through net-next to make 
is_kdump_kernel() (in crash_dump.h) accessible to modules.
That may be a better signal than reset_devices that the
driver should use minimal resources.

http://comments.gmane.org/gmane.linux.network/324737

I'm not sure about the logistics of a SCSI patch depending
on a net-next patch.

---
Rob Elliott    HP Server Storage