linux-kernel - Re: [PATCH 1/8] blk-mq: add blk_mq_alloc_request

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Message-ID: <CAF1ivSYpbzPF+5_e+hEKZ_-t7=UhijULbkvF=SodSF7FD5YS-A@mail.gmail.com>
Date:	Tue, 7 Jun 2016 08:27:29 -0700
From:	Ming Lin <mlin@...nel.org>
To:	Keith Busch <keith.busch@...el.com>
Cc:	Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
	linux-nvme@...ts.infradead.org, linux-block@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>,
	Ming Lin <ming.l@....samsung.com>
Subject: Re: [PATCH 1/8] blk-mq: add blk_mq_alloc_request_hctx

On Tue, Jun 7, 2016 at 7:57 AM, Keith Busch <keith.busch@...el.com> wrote:
> On Mon, Jun 06, 2016 at 11:21:52PM +0200, Christoph Hellwig wrote:
>> +struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
>> +             unsigned int flags, unsigned int hctx_idx)
>> +{
>> +     struct blk_mq_hw_ctx *hctx;
>> +     struct blk_mq_ctx *ctx;
>> +     struct request *rq;
>> +     struct blk_mq_alloc_data alloc_data;
>> +     int ret;
>> +
>> +     ret = blk_queue_enter(q, flags & BLK_MQ_REQ_NOWAIT);
>> +     if (ret)
>> +             return ERR_PTR(ret);
>> +
>> +     hctx = q->queue_hw_ctx[hctx_idx];
>
> We probably want to check 'if (hctx_idx < q->nr_hw_queues)' before
> getting the hctx. Even if hctx_idx was origially valid, it's possible
> (though unlikely) blk_queue_enter waits on reallocating h/w contexts,
> which can make hctx_idx invalid.

Yes, I'll update it.