From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Wu Fengguang <fengguang.wu@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andi Kleen <andi.kleen@intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] pagemap: fix wrong KPF_THP on slab pages
Date: Tue, 25 Sep 2012 13:05:15 -0400 [thread overview]
Message-ID: <1348592715-31006-1-git-send-email-n-horiguchi@ah.jp.nec.com> (raw)
In-Reply-To: <CAHGf_=rbyk1UFGwyQ0BSN3qM_K+5J3Q-Aj=xjNDZFrTrZ6a3dw@mail.gmail.com>
On Tue, Sep 25, 2012 at 11:59:51AM -0400, KOSAKI Motohiro wrote:
> On Tue, Sep 25, 2012 at 9:56 AM, Naoya Horiguchi
> <n-horiguchi@ah.jp.nec.com> 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 <n-horiguchi@ah.jp.nec.com>
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 <n-horiguchi@ah.jp.nec.com>
---
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;
/*
--
1.7.11.4
--
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next prev parent reply other threads:[~2012-09-25 17:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-25 13:56 Naoya Horiguchi
2012-09-25 15:59 ` KOSAKI Motohiro
2012-09-25 17:05 ` Naoya Horiguchi [this message]
2012-09-25 19:03 ` KOSAKI Motohiro
2012-09-26 0:20 ` David Rientjes
2012-09-26 2:06 ` Naoya Horiguchi
2012-09-26 2:26 ` David Rientjes
2012-09-26 2:47 ` Fengguang Wu
2012-09-26 4:02 ` Naoya Horiguchi
2012-09-26 6:06 ` Naoya Horiguchi
2012-09-26 7:38 ` Fengguang Wu
2012-09-26 14:42 ` Naoya Horiguchi
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