lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 24 Aug 2020 22:10:49 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: js1304@...il.com Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...nel.org>, Vlastimil Babka <vbabka@...e.cz>, "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>, kernel-team@....com, Joonsoo Kim <iamjoonsoo.kim@....com> Subject: Re: [PATCH for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs On Tue, 25 Aug 2020 13:59:42 +0900 js1304@...il.com wrote: > From: Joonsoo Kim <iamjoonsoo.kim@....com> > > memalloc_nocma_{save/restore} APIs can be used to skip page allocation > on CMA area, but, there is a missing case and the page on CMA area could > be allocated even if APIs are used. This patch handles this case to fix > the potential issue. > > Missing case is an allocation from the pcplist. MIGRATE_MOVABLE pcplist > could have the pages on CMA area so we need to skip it if ALLOC_CMA isn't > specified. > > This patch implements this behaviour by checking allocated page from > the pcplist rather than skipping an allocation from the pcplist entirely. > Skipping the pcplist entirely would result in a mismatch between watermark > check and actual page allocation. And, it requires to break current code > layering that order-0 page is always handled by the pcplist. I'd prefer > to avoid it so this patch uses different way to skip CMA page allocation > from the pcplist. > > ... > > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3341,6 +3341,22 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, > pcp = &this_cpu_ptr(zone->pageset)->pcp; > list = &pcp->lists[migratetype]; > page = __rmqueue_pcplist(zone, migratetype, alloc_flags, pcp, list); > +#ifdef CONFIG_CMA > + if (page) { > + int mt = get_pcppage_migratetype(page); > + > + /* > + * pcp could have the pages on CMA area and we need to skip it > + * when !ALLOC_CMA. Free all pcplist and retry allocation. > + */ > + if (is_migrate_cma(mt) && !(alloc_flags & ALLOC_CMA)) { > + list_add(&page->lru, &pcp->lists[migratetype]); > + pcp->count++; > + free_pcppages_bulk(zone, pcp->count, pcp); > + page = __rmqueue_pcplist(zone, migratetype, alloc_flags, pcp, list); > + } > + } > +#endif > if (page) { > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1); > zone_statistics(preferred_zone, zone); That's a bunch more code on a very hot path to serve an obscure feature which has a single obscure callsite. Can we instead put the burden on that callsite rather than upon everyone? For (dumb) example, teach __gup_longterm_locked() to put the page back if it's CMA and go get another one?
Powered by blists - more mailing lists