linux-kernel - Re: 4.5.0+ panic when setup loop device

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Date:	Thu, 17 Mar 2016 11:26:20 -0700
From:	Jens Axboe <axboe@...nel.dk>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Xiong Zhou <jencce.kernel@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Andreas Herrmann <aherrmann@...e.com>
Subject: Re: 4.5.0+ panic when setup loop device

On 03/17/2016 09:42 AM, Jens Axboe wrote:
> On 03/17/2016 05:01 AM, Thomas Gleixner wrote:
>> On Thu, 17 Mar 2016, Peter Zijlstra wrote:
>>> On Thu, Mar 17, 2016 at 12:39:46PM +0100, Thomas Gleixner wrote:
>>>> But we have to clarify and document whether holes in
>>>> cpu_possible_mask are not
>>>> allowed at all or if code like the above is simply broken.
>>>
>>> So the general rule is that cpumasks can have holes, and exempting one
>>> just muddles the water.
>>>
>>> Therefore I'd call the code just plain broken.
>>
>> Agreed.
>>
>> That macro is not really helping the readability of the code at all. So a
>> simple for_each_possible_cpu() loop would have avoided that wreckage.
>
> Does the attached work? The rest of blk-mq should deal with holes just
> fine, we found some of those issues on sparc. Not sure why this one
> slipped through the cracks.

This might be better, we need to start at -1 to not miss the first 
one... Still untested.

-- 
Jens Axboe


View attachment "blk-mq-discontig-v2.patch" of type "text/x-patch" (1498 bytes)