linux-kernel - Re: [PATCH] [SCSI] libsas: remove expander from dev list on error

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Date:	Wed, 27 Jul 2011 13:32:50 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Luben Tuikov <ltuikov@...oo.com>
Cc:	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"JBottomley@...allels.com" <JBottomley@...allels.com>,
	Jack Wang <jack_wang@...sh.com>
Subject: Re: [PATCH] [SCSI] libsas: remove expander from dev list on error

On Tue, Jul 26, 2011 at 11:10 PM, Luben Tuikov <ltuikov@...oo.com> wrote:
> If expander discovery fails (sas_discover_expander()),
> remove the expander from the port device list
> (sas_ex_discover_expander()), before freeing it. Else
> the list is corrupted and, e.g., when we attempt to send
> SMP commands to other devices, the kernel oopses.
>
> Signed-off-by: Luben Tuikov <ltuikov@...oo.com>
> Reviewed-by: Jack Wang <jack_wang@...sh.com>
> ---
>  drivers/scsi/libsas/sas_expander.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 874e29d..f84084b 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -849,6 +849,9 @@ static struct domain_device *sas_ex_discover_expander(
>
>         res = sas_discover_expander(child);
>         if (res) {
> +               spin_lock_irq(&parent->port->dev_list_lock);
> +               list_del(&child->dev_list_node);
> +               spin_unlock_irq(&parent->port->dev_list_lock);
>                 kfree(child);
>                 return NULL;

Acked-by: Dan Williams <dan.j.williams@...el.com>

...but it raises a couple questions for potential follow on patches:

1/ Do we need to add the device to port->dev_list prior to the
discovery?  Seems cleaner to defer the list_add until after the
discovery has succeeded.

2/ We have unlocked list manipulations in sas_ex_discover_end_dev(),
sas_unregister_common_dev(), and sas_ex_discover_end_dev()

--
Dan
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