On Wed, Apr 06, 2011 at 09:45:55AM -0400, Christoph Hellwig wrote:
> On Tue, Apr 05, 2011 at 05:43:55PM -0400, Matthew Wilcox wrote:
> >
> > We can eliminate the use of the scsi command serial_number, as the race
> > that the driver is checking for cannot happen.
> >
> > Then the driver no longer needs to use the DEF_SCSI_QCMD() macro and no
> > longer acquires the host_lock. This improves performance substantially
> > on high-IOPS workloads.
>
> Looks fine. Note that this somehow clashes with my patch to simply
> remove the serial_number check from mpt2sas. We could just drop my
> smaller patch if this one gets in in a timely fashion.
We should probably split this patch apart into the serial_number removal
and then the host_lock removal anyway.
But I don't think your patch is correct:
- if (scmd_lookup && (scmd_lookup->serial_number ==
- scmd->serial_number))
+ if (scmd_lookup)
rc = FAILED;
else
rc = SUCCESS;
The second part of the conditional is always false (right? because that
command can't be in flight).
So that's (scmd_lookup && 0), which is if (0), so we can just state rc
= SUCCESS. Or is my reasoning faulty somewhere?
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