From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx166.postini.com [74.125.245.166]) by kanga.kvack.org (Postfix) with SMTP id 7AC9E6B002B for ; Tue, 25 Sep 2012 15:04:02 -0400 (EDT) Received: by oagk14 with SMTP id k14so5031729oag.14 for ; Tue, 25 Sep 2012 12:04:01 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1348592715-31006-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1348592715-31006-1-git-send-email-n-horiguchi@ah.jp.nec.com> From: KOSAKI Motohiro Date: Tue, 25 Sep 2012 15:03:41 -0400 Message-ID: Subject: Re: [PATCH] pagemap: fix wrong KPF_THP on slab pages Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Wu Fengguang , Andrew Morton , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue, Sep 25, 2012 at 1:05 PM, Naoya Horiguchi wrote: > On Tue, Sep 25, 2012 at 11:59:51AM -0400, KOSAKI Motohiro wrote: >> On Tue, Sep 25, 2012 at 9:56 AM, Naoya Horiguchi >> wrote: >> > KPF_THP can be set on non-huge compound pages like slab pages, because >> > PageTransCompound only sees PG_head and PG_tail. Obviously this is a bug >> > and breaks user space applications which look for thp via /proc/kpageflags. >> > Currently thp is constructed only on anonymous pages, so this patch makes >> > KPF_THP be set when both of PageAnon and PageTransCompound are true. >> >> Indeed. Please add some comment too. > > Sure. I send revised one. > > Thanks, > Naoya > --- > From: Naoya Horiguchi > Date: Mon, 24 Sep 2012 16:28:30 -0400 > Subject: [PATCH v2] pagemap: fix wrong KPF_THP on slab pages > > KPF_THP can be set on non-huge compound pages like slab pages, because > PageTransCompound only sees PG_head and PG_tail. Obviously this is a bug > and breaks user space applications which look for thp via /proc/kpageflags. > Currently thp is constructed only on anonymous pages, so this patch makes > KPF_THP be set when both of PageAnon and PageTransCompound are true. > > Changelog in v2: > - add a comment in code > > Signed-off-by: Naoya Horiguchi > --- > fs/proc/page.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/page.c b/fs/proc/page.c > index 7fcd0d6..f7cd2f6c 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -115,7 +115,12 @@ u64 stable_page_flags(struct page *page) > u |= 1 << KPF_COMPOUND_TAIL; > if (PageHuge(page)) > u |= 1 << KPF_HUGE; > - else if (PageTransCompound(page)) > + /* > + * Since THP is relevant only for anonymous pages so far, we check it > + * explicitly with PageAnon. Otherwise thp is confounded with non-huge > + * compound pages like slab pages. > + */ > + else if (PageTransCompound(page) && PageAnon(page)) > u |= 1 << KPF_THP; Looks good to me. Acked-by: KOSAKI Motohiro -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org