linux-kernel - Re: [PATCH] cciss: Ignore stale commands after reboot

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Date:	Thu, 02 Jul 2009 11:36:43 +0200
From:	Hannes Reinecke <hare@...e.de>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	scameron@...rdog.cca.cpqcorp.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cciss: Ignore stale commands after reboot

Jens Axboe wrote:
> On Thu, Jul 02 2009, Hannes Reinecke wrote:
>> Jens Axboe wrote:
>>> On Thu, Jul 02 2009, Hannes Reinecke wrote:
>>>> When doing an unexpected shutdown like kexec the cciss
>>>> firmware might still have some commands in flight, which
>>>> it is trying to complete.
>>>> The driver is doing it's best on resetting the HBA,
>>>> but sadly there's a firmware issue causing the firmware
>>>> _not_ to abort or drop old commands.
>>>> So the firmware will send us commands which we haven't
>>>> accounted for, causing the driver to panic.
>>>>
>>>> With this patch we're just ignoring these commands as
>>>> there is nothing we could be doing with them anyway.
>>>>
>>>> Signed-off-by: Hannes Reinecke <hare@...e.de>
>>>> ---
>>>>  drivers/block/cciss.c     |   14 ++++++++++++--
>>>>  drivers/block/cciss_cmd.h |    1 +
>>>>  2 files changed, 13 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
>>>> index c7a527c..8dd4c0d 100644
>>>> --- a/drivers/block/cciss.c
>>>> +++ b/drivers/block/cciss.c
>>>> @@ -226,7 +226,16 @@ static inline void addQ(struct hlist_head *list, CommandList_struct *c)
>>>>
>>>>  static inline void removeQ(CommandList_struct *c)
>>>>  {
>>>> -	if (WARN_ON(hlist_unhashed(&c->list)))
>>>> +	/*
>>>> +	 * After kexec/dump some commands might still
>>>> +	 * be in flight, which the firmware will try
>>>> +	 * to complete. Resetting the firmware doesn't work
>>>> +	 * with old fw revisions, so we have to mark
>>>> +	 * them off as 'stale' to prevent the driver from
>>>> +	 * falling over.
>>>> +	 */
>>>> +	if (unlikely(hlist_unhashed(&c->list))) {
>>>> +		c->cmd_type = CMD_MSG_STALE;
>>>>  		return;
>>>>
>>>>       hlist_del_init(&c->list);
>>> Ehm, that looks rather dangerous. What's the level of testing this patch
>>> received?
>>>
>> Where is the danger here?
> 
> The danger is that the patch doesn't even compile :-)
> At least it had the { at the end of the if, otherwise it would have been
> insta-hang.
> 
Bah. Should've said so.
That's what you get when you cut-n-paste from a different version.

OK, resending.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@...e.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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