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

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Message-ID: <20090702082804.GP23611@kernel.dk>
Date:	Thu, 2 Jul 2009 10:28:04 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Hannes Reinecke <hare@...e.de>
Cc:	scameron@...rdog.cca.cpqcorp.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cciss: Ignore stale commands after reboot

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?

-- 
Jens Axboe

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