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SubjectRe: [PATCH 006 of 6] md: Add support for reshape of a raid6
On Thu, 22 Feb 2007 00:36:22 +0100
Oleg Verych <olecom@flower.upol.cz> wrote:

> > From: Andrew Morton
> > Newsgroups: gmane.linux.raid,gmane.linux.kernel
> > Subject: Re: [PATCH 006 of 6] md: Add support for reshape of a raid6
> > Date: Wed, 21 Feb 2007 14:48:06 -0800
>
> Hallo.
>
> > On Tue, 20 Feb 2007 17:35:16 +1100
> > NeilBrown <neilb@suse.de> wrote:
> >
> >> + for (i = conf->raid_disks ; i-- ; ) {
> >
> > That statement should be dragged out, shot, stomped on then ceremonially
> > incinerated.
> >
> > What's wrong with doing
> >
> > for (i = 0; i < conf->raid_disks; i++) {
> >
> > in a manner which can be understood without alcoholic fortification?
> >
> > ho hum.
>
> In case someone likes to do job, GCC usually ought to do, i would
> suggest something like this instead:
>
> if (expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
> /* Need to write out all blocks after computing P&Q */
> - sh->disks = conf->raid_disks;
> + i = conf->raid_disks;
> + sh->disks = i;
> - sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
> - conf->raid_disks);
> + sh->pd_idx = stripe_to_pdidx(sh->sector, conf, i);
>
> compute_parity6(sh, RECONSTRUCT_WRITE);
> - for (i = conf->raid_disks ; i-- ; ) {
> + do {
> set_bit(R5_LOCKED, &sh->dev[i].flags);
> locked++;
> set_bit(R5_Wantwrite, &sh->dev[i].flags);
> - }
> + } while (--i);
>
> clear_bit(STRIPE_EXPANDING, &sh->state);
> } else if (expanded) {
>
> In any case this is subject of scripts/bloat-o-meter.

This:

--- a/drivers/md/raid5.c~a
+++ a/drivers/md/raid5.c
@@ -2364,7 +2364,7 @@ static void handle_stripe6(struct stripe
sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
conf->raid_disks);
compute_parity6(sh, RECONSTRUCT_WRITE);
- for (i = conf->raid_disks ; i-- ; ) {
+ for (i = 0; i < conf->raid_disks; ++) {
set_bit(R5_LOCKED, &sh->dev[i].flags);
locked++;
set_bit(R5_Wantwrite, &sh->dev[i].flags);
_
reduces the size of drivers/md/raid5.o's .text by two bytes.


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