On Mon, Feb 25, 2008 at 07:04:20AM -0800, James Bottomley wrote:
> On Mon, 2008-02-25 at 15:58 +0100, Andi Kleen wrote:
> > On Mon, Feb 25, 2008 at 06:46:58AM -0800, James Bottomley wrote:
> > >
> > > On Mon, 2008-02-25 at 00:35 +0100, Andi Kleen wrote:
> > > > Should not be needed because the block layer bounces that all.
> > > >
> > > > Signed-off-by: Andi Kleen <ak@xxxxxxx>
> > > >
> > > > ---
> > > > drivers/scsi/scsi_scan.c | 6 ++----
> > > > 1 file changed, 2 insertions(+), 4 deletions(-)
> > > >
> > > > Index: linux/drivers/scsi/scsi_scan.c
> > > > ===================================================================
> > > > --- linux.orig/drivers/scsi/scsi_scan.c
> > > > +++ linux/drivers/scsi/scsi_scan.c
> > > > @@ -1010,8 +1010,7 @@ static int scsi_probe_and_add_lun(struct
> > > > if (!sdev)
> > > > goto out;
> > > >
> > > > - result = kmalloc(result_len, GFP_ATOMIC |
> > > > - ((shost->unchecked_isa_dma) ? __GFP_DMA : 0));
> > > > + result = kmalloc(result_len, GFP_ATOMIC);
> > > > if (!result)
> > > > goto out_free_sdev;
> > > >
> > > > @@ -1328,8 +1327,7 @@ static int scsi_report_lun_scan(struct s
> > > > * prevent us from finding any LUNs on this target.
> > > > */
> > > > length = (max_scsi_report_luns + 1) * sizeof(struct scsi_lun);
> > > > - lun_data = kmalloc(length, GFP_ATOMIC |
> > > > - (sdev->host->unchecked_isa_dma ? __GFP_DMA : 0));
> > > > + lun_data = kmalloc(length, GFP_ATOMIC);
> > > > if (!lun_data) {
> > > > printk(ALLOC_FAILURE_MSG, __FUNCTION__);
> > > > goto out;
> > >
> > > Andi, this can't be right.
> >
> > You mean it is incorrect or just not optimal?
>
> It's not optimal ... but that's sufficient an objection.
>
> > >
> > > You're removing something that's actually useful. I'm happy to
> > > substitute this kmalloc for kmalloc_mask on the device dma mask which
> > > will do the same thing and so junk unchecked_isa_dma() that way (and
> > > actually fix us up for other weird mask devices), but just using
> > > ZONE_NORMAL is wrong because we'll then bounce all the time for
> > > something we knew a priori how to avoid.
> >
> > That would require adding a separate mask just for this to the
> > template. I figured the SCSI scan was not performance critical
> > so a few more copies just for this case was an ok trade off
> > for simpler code.
>
> Why? We already have the device; can't we just use its mask?
These ISA drivers I worked with definitely don't know
anything about a device in any form.
Also there is the issue that 50+% of the ISA drivers actually
don't need it even if they had a ISA device.
>
> > You think it makes sense to optimize scsi scan?
>
> It makes sense to use information we already know to optimise the path,
In this case we would need to add a special new field for this
to the SCSI template (assume unchecked_isa_dma is already gone).
You think that is worth it?
-Andi
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