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Subject: Re: [PATCH v11 3/3] scsi: set max_bio_bytes with queue max sectors
To:     Changheun Lee <nanich.lee@samsung.com>, hch@infradead.org,
        Johannes.Thumshirn@wdc.com, alex_y_xu@yahoo.ca,
        asml.silence@gmail.com, axboe@kernel.dk, bgoncalv@redhat.com,
        damien.lemoal@wdc.com, gregkh@linuxfoundation.org,
        jaegeuk@kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, ming.lei@redhat.com, osandov@fb.com,
        patchwork-bot@kernel.org, tj@kernel.org, tom.leiming@gmail.com,
        yi.zhang@redhat.com
Cc:     jisoo2146.oh@samsung.com, junho89.kim@samsung.com,
        mj0123.lee@samsung.com, seunghwan.hyun@samsung.com,
        sookwan7.kim@samsung.com, woosung2.lee@samsung.com,
        yt0928.kim@samsung.com
References: <20210602121037.11083-1-nanich.lee@samsung.com>
 <CGME20210602122912epcas1p4faff714cc9457b0d482fc1a4b63a49a9@epcas1p4.samsung.com>
 <20210602121037.11083-4-nanich.lee@samsung.com>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <10c02317-7528-bbad-3cfb-75db54d2ab91@acm.org>
Date:   Wed, 2 Jun 2021 12:04:04 -0700
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On 6/2/21 5:10 AM, Changheun Lee wrote:
> Set max_bio_bytes same with queue max sectors. It will lead to fast bio
> submit when bio size is over than queue max sectors. And it might be helpful
> to align submit bio size in some case.
> 
> Signed-off-by: Changheun Lee <nanich.lee@samsung.com>
> ---
>  drivers/scsi/scsi_lib.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 532304d42f00..f6269268b0e0 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1837,6 +1837,8 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
>  	blk_queue_virt_boundary(q, shost->virt_boundary_mask);
>  	dma_set_max_seg_size(dev, queue_max_segment_size(q));
>  
> +	blk_queue_max_bio_bytes(q, queue_max_sectors(q));
> +
>  	/*
>  	 * Set a reasonable default alignment:  The larger of 32-byte (dword),
>  	 * which is a common minimum for HBAs, and the minimum DMA alignment,

Has this patch been tested with dm-crypt on top of a SCSI device? I'm
concerned that this patch will trigger data corruption with dm-crypt on
top because the above change will make the following dm-crypt code fail
for a sufficiently large bio:

		bio_add_page(clone, page, len, 0);

When testing dm-crypt on top of this patch series, please change the
above dm-crypt code into the following before running any tests:

		WARN_ON(bio_add_page(clone, page, len, 0) < len);

Thanks,

Bart.