Message-ID: <538F3B04.1080007@kernel.dk>
Date: Wed, 04 Jun 2014 09:28:04 -0600
From: Jens Axboe <axboe@kernel.dk>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0
MIME-Version: 1.0
To: Christoph Hellwig <hch@infradead.org>
CC: Shaohua Li <shli@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [patch]blk-mq: blk_mq_tag_to_rq should handle flush request
References: <20140510040023.GA13788@kernel.org> <5388912F.7010609@kernel.dk> <20140604111133.GA7826@infradead.org> <538F2A11.4060800@kernel.dk> <20140604142012.GA20056@infradead.org> <538F331F.60101@kernel.dk> <20140604145803.GA7826@infradead.org> <538F34FB.7050003@kernel.dk> <20140604150508.GA21551@infradead.org> <538F365C.8050604@kernel.dk> <20140604152217.GA8781@infradead.org>
In-Reply-To: <20140604152217.GA8781@infradead.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org

On 2014-06-04 09:22, Christoph Hellwig wrote:
> On Wed, Jun 04, 2014 at 09:08:12AM -0600, Jens Axboe wrote:
>> On 2014-06-04 09:05, Christoph Hellwig wrote:
>>> On Wed, Jun 04, 2014 at 09:02:19AM -0600, Jens Axboe wrote:
>>>> OK strange, there hasn't been that much churn since the last rebase.
>>>> In my for-linus, there's a patch for a single queue crash, but that
>>>> should just hit for the removal case. And then there's the atomic
>>>> schedule patch, but that issue was actually in the code base for
>>>> about a month, so not a new one either.
>>>
>>> You're request initializaion optimization doesn't set up req->cmd and
>>> thus causes all BLOCK_PC I/O (including the SCSI LUN scan) to crash and
>>> burn.  The trivial fix is on your way.
>>
>> OK. That'll arguably be a good cleanup as well, getting that
>> initialized in the right place. I hate the 'lets clear all the
>> memory' part of rq init, it's not super cheap to do.
>
> What would the right place be?  We don't really know if a request is
> going to be used for BLOCK_PC purposes until it has been returned to
> the caller.

Probably split the init, so instead of directly assigning the type as 
BLOCK_PC (or similar), then have an init function for that that clears 
the parts.

> I also found another issue when just initializing req->cmd instead
> of blindly reverting the patch due to the lack of req->biotail
> initialization.  For now I'll got back to a revert of that patch
> for my scsi-mq tree, and I'd prefer to keep that for mainline as well
> until this has been throughoutly tested.

That's fine. I'll get this cleaned up, or consider a revert in the block 
tree as well.

-- 
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/