Re: [PATCH v12 3/3] ufs: set max_bio_bytes with queue max sectors

[Bart Van Assche <bvanassche@acm.org>]

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@samsung.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.