linux-kernel - Re: [PATCH v11 3/3] scsi: set max_bio

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Date:   Thu,  3 Jun 2021 21:43:32 +0900
From:   Changheun Lee <nanich.lee@...sung.com>
To:     Johannes.Thumshirn@....com, alex_y_xu@...oo.ca,
        asml.silence@...il.com, axboe@...nel.dk, bgoncalv@...hat.com,
        bvanassche@....org, damien.lemoal@....com,
        gregkh@...uxfoundation.org, hch@...radead.org, jaegeuk@...nel.org,
        linux-block@...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 v11 3/3] scsi: set max_bio_bytes with queue max sectors

> > On 2021/06/02 21:29, 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/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));
> > 
> > Doing this unconditionally for all scsi block devices is probably not a good
> > idea. Cannot this be moved to the LLD handling the devices that actually need it ?
> 
> OK, I'll try to check more nice location in LLD.
> 
> > 
> > > +
> > >  	/*
> > >  	 * Set a reasonable default alignment:  The larger of 32-byte (dword),
> > >  	 * which is a common minimum for HBAs, and the minimum DMA alignment,
> > > 
> > 
> > 
> > -- 
> > Damien Le Moal
> > Western Digital Research
> 
> Thank you,
> Changheun Lee

I think below location might be good. feedback to me please.

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 3eb54937f1d8..0f97b7d275ee 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -4831,6 +4831,9 @@ static int ufshcd_slave_alloc(struct scsi_device *sdev)
 
 	ufshcd_get_lu_power_on_wp_status(hba, sdev);
 
+	blk_queue_max_bio_bytes(sdev->request_queue,
+				queue_max_sectors(sdev->request_queue));
+
 	return 0;
 }

Thank you,
Changheun Lee