linux-kernel - Re: swiotlb default size (64 MB) too small?

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Date:	Wed, 28 Jan 2009 08:31:07 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	stefanr@...6.in-berlin.de
Cc:	fujita.tomonori@....ntt.co.jp,
	linux1394-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: swiotlb default size (64 MB) too small?

On Tue, 27 Jan 2009 18:03:40 +0100 (CET)
Stefan Richter <stefanr@...6.in-berlin.de> wrote:

> On 27 Jan, FUJITA Tomonori wrote at LSML and LKML:
> [I wrote]
> >> > *) The report does not sound like there was a DMA mappig leak caused by
> >> > copying between usb-storage and firewire-sbp2.  Else he would have hit
> >> > the problem again even with increased swiotlb default size.
> 
> > Hmm, we don't have leak here?
> > 
> > =
> > From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> > Subject: [PATCH] fw-sbp2: fix dma mapping leak on the failure path
> > 
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> > ---
> >  drivers/firewire/fw-sbp2.c |   12 +++++++++++-
> >  1 files changed, 11 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
> > index e88d506..d40910d 100644
> > --- a/drivers/firewire/fw-sbp2.c
> > +++ b/drivers/firewire/fw-sbp2.c
> > @@ -1491,8 +1491,18 @@ static int sbp2_scsi_queuecommand(struct scsi_cmnd *cmd, scsi_done_fn_t done)
> >  	orb->base.request_bus =
> >  		dma_map_single(device->card->device, &orb->request,
> >  			       sizeof(orb->request), DMA_TO_DEVICE);
> > -	if (dma_mapping_error(device->card->device, orb->base.request_bus))
> > +	if (dma_mapping_error(device->card->device, orb->base.request_bus)) {
> > +		if (scsi_sg_count(cmd)) {
> > +			dma_unmap_sg(device->card->device, scsi_sglist(cmd),
> > +				     scsi_sg_count(cmd),
> > +				     cmd->sc_data_direction);
> > +			dma_unmap_single(device->card->device,
> > +					 orb->page_table_bus,
> > +					 sizeof(orb->page_table),
> > +					 DMA_TO_DEVICE);
> > +		}
> >  		goto out;
> > +	}
> >  
> >  	sbp2_send_orb(&orb->base, lu, lu->tgt->node_id, generation,
> >  		      lu->command_block_agent_address + SBP2_ORB_POINTER);
> 
> Yes, we do have a leak there.  Thanks a lot for checking the code.
> 
> There is one thing missing in the fix:  Even with scsi_sg_count(cmd) !=
> 0, there is sometimes no orb->page_table to unmap.  It's when the
> scatterlist was mapped into a single physical segment.
> 
> 
> From: Stefan Richter <stefanr@...6.in-berlin.de>
> Subject: firewire: sbp2: fix DMA mapping leak on the failure path
> 
> Reported-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> who also provided a first version of the fix.
> 
> Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
> ---
>  drivers/firewire/fw-sbp2.c |   27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> Index: linux/drivers/firewire/fw-sbp2.c
> ===================================================================
> --- linux.orig/drivers/firewire/fw-sbp2.c
> +++ linux/drivers/firewire/fw-sbp2.c
> @@ -1323,6 +1323,19 @@ static unsigned int sbp2_status_to_sense
>  	}
>  }
>  
> +static void sbp2_unmap_scatterlist(struct device *card_device,
> +				   struct sbp2_command_orb *orb)
> +{
> +	if (scsi_sg_count(orb->cmd))
> +		dma_unmap_sg(card_device, scsi_sglist(orb->cmd),
> +			     scsi_sg_count(orb->cmd),
> +			     orb->cmd->sc_data_direction);
> +
> +	if (orb->page_table_bus)
> +		dma_unmap_single(card_device, orb->page_table_bus,
> +				 sizeof(orb->page_table), DMA_TO_DEVICE);

Well, this does not look correct since zero can be a valid dma
address.

static void sbp2_unmap_scatterlist(struct device *card_device,
				   struct sbp2_command_orb *orb)
{
	if (scsi_sg_count(orb->cmd))
		dma_unmap_sg(card_device, scsi_sglist(orb->cmd),
			     scsi_sg_count(orb->cmd),
			     orb->cmd->sc_data_direction);

	if (scsi_sg_count(orb->cmd) > 1)
		dma_unmap_single(card_device, orb->page_table_bus,
				 sizeof(orb->page_table), DMA_TO_DEVICE);


Well, looks cranky a bit but firewire is cranky for me :)
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