Re: [PATCH 006 of 6] md: Add support for reshape of a raid6

From: Rafael J. Wysocki
Date: Wed Feb 21 2007 - 19:03:15 EST


On Thursday, 22 February 2007 00:58, Andrew Morton wrote:
> On Thu, 22 Feb 2007 00:36:22 +0100
> Oleg Verych <olecom@xxxxxxxxxxxxxx> 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@xxxxxxx> 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; ++) {

I guess it should be

+ for (i = 0; i < conf->raid_disks; i++)

> set_bit(R5_LOCKED, &sh->dev[i].flags);
> locked++;
> set_bit(R5_Wantwrite, &sh->dev[i].flags);
> _
-
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