linux-kernel - Re: [PATCH] SCSI IOCTL: Check for device deletion [was Re: __elv_add

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Message-ID: <4DDF3A07.7040106@fusionio.com>
Date:	Fri, 27 May 2011 07:43:35 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	Parag Warudkar <parag.lkml@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Linux SCSI List <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH] SCSI IOCTL: Check for device deletion [was Re:  __elv_add_request
 OOPS]

On 2011-05-27 05:53, James Bottomley wrote:
> On Wed, 2011-05-25 at 15:52 -0500, James Bottomley wrote:
>> On Wed, 2011-05-25 at 16:42 -0400, Parag Warudkar wrote:
>>> Yeah - that makes sense. By that logic, looks like we can only disallow 
>>> for SDEV_DEL (if we decide to do that check here).
>>
>> I don't think this is the root cause.  I think q is non-NULL but has
>> already been released, so we're just getting a NULL deref on the actual
>> list head.
>>
>> Does this fix it?  It adds the refcounting at approximately the correct
>> places.  Of course, we'll now be trying elevator operations on an extant
>> queue but one whose elevator functions have been destroyed, so there are
>> probably additional state guards to place.
>>
>> James
>>
>> ---
>>
>> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
>> index 58584dc..44e8ca3 100644
>> --- a/drivers/scsi/scsi_scan.c
>> +++ b/drivers/scsi/scsi_scan.c
>> @@ -297,7 +297,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
>>  		kfree(sdev);
>>  		goto out;
>>  	}
>> -
>> +	blk_get_queue(sdev->request_queue);
> 
> Apparently we can't do this because blk_[put|get]_queue aren't exported
> for use in modules (and SCSI can be modular), so this caused a build
> failure in linux-next.

I'll just export them.

-- 
Jens Axboe

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