On Mon, 23 Aug 2010, Andrew Morton wrote:
> > > > diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c
> > > > --- a/drivers/md/dm-region-hash.c
> > > > +++ b/drivers/md/dm-region-hash.c
> > > > @@ -289,8 +289,12 @@ static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
> > > > struct dm_region *reg, *nreg;
> > > >
> > > > nreg = mempool_alloc(rh->region_pool, GFP_ATOMIC);
> > > > - if (unlikely(!nreg))
> > > > - nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);
> > > > + if (unlikely(!nreg)) {
> > > > + /* FIXME: this may potentially loop forever */
> > > > + do {
> > > > + nreg = kmalloc(sizeof(*nreg), GFP_NOIO);
> > > > + } while (!nreg);
> > > > + }
> > > >
> > > > nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
> > > > DM_RH_CLEAN : DM_RH_NOSYNC;
> > >
> > > erm.
> > >
> > > The reason for adding GFP_NOFAIL in the first place was my observation
> > > that the kernel contained lots of open-coded retry-for-ever loops.
> > >
> > > All of these are wrong, bad, buggy and mustfix. So we consolidated the
> > > wrongbadbuggymustfix concept into the core MM so that miscreants could
> > > be easily identified and hopefully fixed.
> > >
> >
> > That consolidation would have been unnecessary, then, since all
> > allocations with order < PAGE_ALLOC_COSTLY_ORDER automatically loop
> > indefinitely in the page allocator.
>
> The difference is that an order-0 !__GFP_NOFAIL allocation attempt can
> fail due to oom-killing. Unless someone broke that.
>
This is GFP_NOIO, which all the allocations in this patchset are (or
GFP_NOFS), so the oom killer isn't involved.
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