Messages in this thread Patch in this message | | | Date | Thu, 24 Nov 2011 10:04:09 +0100 | From | Johannes Weiner <> | Subject | Re: [patch 5/8] mm: memcg: remove unneeded checks from newpage_charge() |
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On Thu, Nov 24, 2011 at 09:04:43AM +0900, KAMEZAWA Hiroyuki wrote: > On Wed, 23 Nov 2011 16:42:28 +0100 > Johannes Weiner <hannes@cmpxchg.org> wrote: > > > From: Johannes Weiner <jweiner@redhat.com> > > > > All callsites pass in freshly allocated pages and a valid mm. As a > > result, all checks pertaining the page's mapcount, page->mapping or > > the fallback to init_mm are unneeded. > > > > Signed-off-by: Johannes Weiner <jweiner@redhat.com> > > Hmm, it's true now. But for making clear our assumption to all readers of code, > > could you add > VM_BUG_ON(!mm || page_mapped(page) || (page->mapping && !PageAnon(page)) ?
Of course. Please find the delta patch below. I broke them up into three separate checks to make the problem easier to find if the BUG triggers.
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Thank you.
--- From: Johannes Weiner <jweiner@redhat.com> Subject: mm: memcg: remove unneeded checks from newpage_charge() fix
Document page state assumptions and catch if they are violated in newpage_charge().
Signed-off-by: Johannes Weiner <jweiner@redhat.com> --- mm/memcontrol.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0d10be4..f338018 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2679,6 +2679,9 @@ int mem_cgroup_newpage_charge(struct page *page, { if (mem_cgroup_disabled()) return 0; + VM_BUG_ON(page_mapped(page)); + VM_BUG_ON(page->mapping && !PageAnon(page)); + VM_BUG_ON(!mm); return mem_cgroup_charge_common(page, mm, gfp_mask, MEM_CGROUP_CHARGE_TYPE_MAPPED); } -- 1.7.6.4
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