linux-kernel - Re: [PATCH v12 3/3] ufs: set max_bio

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Date:   Fri, 4 Jun 2021 09:11:09 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Changheun Lee <nanich.lee@...sung.com>, Johannes.Thumshirn@....com,
        alex_y_xu@...oo.ca, asml.silence@...il.com, axboe@...nel.dk,
        bgoncalv@...hat.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, cang@...eaurora.org,
        avri.altman@....com, alim.akhtar@...sung.com,
        damien.lemoal@....com, gregkh@...uxfoundation.org,
        hch@...radead.org, jaegeuk@...nel.org, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        ming.lei@...hat.com, osandov@...com, patchwork-bot@...nel.org,
        tj@...nel.org, tom.leiming@...il.com, yi.zhang@...hat.com
Cc:     jisoo2146.oh@...sung.com, junho89.kim@...sung.com,
        mj0123.lee@...sung.com, seunghwan.hyun@...sung.com,
        sookwan7.kim@...sung.com, woosung2.lee@...sung.com,
        yt0928.kim@...sung.com
Subject: Re: [PATCH v12 3/3] ufs: set max_bio_bytes with queue max sectors

On 6/3/21 10:03 PM, 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@...sung.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 3eb54937f1d8..37365a726517 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -4858,6 +4858,7 @@ static int ufshcd_slave_configure(struct scsi_device *sdev)
>  {
>  	struct ufs_hba *hba = shost_priv(sdev->host);
>  	struct request_queue *q = sdev->request_queue;
> +	unsigned int max_bio_bytes;
>  
>  	blk_queue_update_dma_pad(q, PRDT_DATA_BYTE_COUNT_PAD - 1);
>  	if (hba->quirks & UFSHCD_QUIRK_ALIGN_SG_WITH_PAGE_SIZE)
> @@ -4868,6 +4869,10 @@ static int ufshcd_slave_configure(struct scsi_device *sdev)
>  
>  	ufshcd_crypto_setup_rq_keyslot_manager(hba, q);
>  
> +	if (!check_shl_overflow(queue_max_sectors(q),
> +				SECTOR_SHIFT, &max_bio_bytes))
> +		blk_queue_max_bio_bytes(q, max_bio_bytes);
> +
>  	return 0;
>  }

Just like previous versions of this patch series, this approach will
trigger data corruption if dm-crypt is stacked on top of the UFS driver
since ufs_max_sectors << SECTOR_SHIFT = 1024 * 512 is less than the size
of the dm-crypt buffer (BIO_MAX_VECS << PAGE_SHIFT = 256 * 4096).

I am not recommending to increase max_sectors for the UFS driver. We
need a solution that is independent of the dm-crypt internals.

Bart.