linux-kernel - Re: [PATCH] block: set rq->cmd_flags with bio->opf instead of data->cmd

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Date:   Mon, 28 Jan 2019 16:05:47 +0000
From:   John Garry <john.garry@...wei.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     "chenxiang (M)" <chenxiang66@...ilicon.com>,
        <jejb@...ux.vnet.ibm.com>, <martin.petersen@...cle.com>,
        <linuxarm@...wei.com>, <linux-scsi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <axboe@...nel.dk>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [PATCH] block: set rq->cmd_flags with bio->opf instead of
 data->cmd_flags when bio is not Null

On 28/01/2019 15:57, Christoph Hellwig wrote:
> On Mon, Jan 28, 2019 at 03:36:58PM +0000, John Garry wrote:
>> As I understood, the problem is the scenario of calling
>> blk_mq_make_request()->bio_integrity_prep() where we then allocate a bio
>> integrity payload in calling bio_integrity_alloc().
>>
>> In this case, bio_integrity_alloc() sets bio->bi_opf |= REQ_INTEGRITY, which
>> is no longer consistent with data.cmd_flags.
>
> I don't see how that could happen:
>
> static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
> {
> 	...
>
> 	if (!bio_integrity_prep(bio))
> 		return BLK_QC_T_NONE;
>
> 	...
>
> 	data.cmd_flags = bio->bi_opf;
>         rq = blk_mq_get_request(q, bio, &data);
>
>

Your code is different to mine, then I see that this has been fixed in 
5.0-rc3:

commit 7809167da5c86fd6bf309b33dee7a797e263342f
Author: Ming Lei <ming.lei@...hat.com>
Date:   Wed Jan 16 19:08:15 2019 +0800

     block: don't lose track of REQ_INTEGRITY flag

     We need to pass bio->bi_opf after bio intergrity preparing, otherwise
     the flag of REQ_INTEGRITY may not be set on the allocated request, then
     breaks block integrity.

     Fixes: f9afca4d367b ("blk-mq: pass in request/bio flags to queue 
mapping")
     Cc: Hannes Reinecke <hare@...e.com>
     Cc: Keith Busch <keith.busch@...el.com>
     Signed-off-by: Ming Lei <ming.lei@...hat.com>
     Signed-off-by: Jens Axboe <axboe@...nel.dk>


Sorry for the noise,
John

> .
>