On Wednesday, July 23, 2014 12:36:01 PM Tejun Heo wrote:
> Hello,
>
> On Wed, Jul 23, 2014 at 06:31:58PM +0200, Bartlomiej Zolnierkiewicz wrote:
> > Hmmm, wasn't ATA_MAX_QUEUE used before not ATA_MAX_QUEUE - 1?
> >
> > It seems that after your patch the loop in the ata_qc_new() will use
> > only 30 tags and not 31 ones?
>
> It was always 31 (ATA_MAX_QUEUE - 1) with the tag 31 reserved for EH
> commands. The previous patch just used limit value which is one too
> high. I'm planning to change that but this is the way it has always
> been.
I see, thanks for explaining this.
BTW:
/* the last tag is reserved for internal command. */
if (tag == ATA_TAG_INTERNAL)
continue;
in ata_qc_new()'s loop now becomes a dead code (loop will be done
maximum ATA_MAX_QUEUE - 2 times and ATA_TAG_INTERNAL is defined
as ATA_MAX_QUEUE - 1). Compiler can probably optimize it away so
as a bonus of your patch we may get one condition check less in
a hot-path. :)
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics
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