* [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages
@ 2012-09-26 20:27 Naoya Horiguchi
2012-09-27 1:17 ` David Rientjes
2012-09-27 1:20 ` Fengguang Wu
0 siblings, 2 replies; 3+ messages in thread
From: Naoya Horiguchi @ 2012-09-26 20:27 UTC (permalink / raw)
To: Wu Fengguang, Andrew Morton
Cc: KOSAKI Motohiro, David Rientjes, Andi Kleen, linux-mm,
linux-kernel
KPF_THP can be set on non-huge compound pages (like slab pages or pages
allocated by drivers with __GFP_COMP) because PageTransCompound only
checks PG_head and PG_tail. Obviously this is a bug and breaks user space
applications which look for thp via /proc/kpageflags.
This patch rules out setting KPF_THP wrongly by additionally checking
PageLRU on the head pages.
Changelog in v4:
- check PageLRU with compound_trans_head()
- fix patch subject again
Changelog in v3:
- check PageSlab instead of PageAnon
- fix patch subject
Changelog in v2:
- add a comment in code
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
---
fs/proc/page.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git v3.6-rc6.orig/fs/proc/page.c v3.6-rc6/fs/proc/page.c
index 7fcd0d6..b8730d9 100644
--- v3.6-rc6.orig/fs/proc/page.c
+++ v3.6-rc6/fs/proc/page.c
@@ -115,7 +115,13 @@ u64 stable_page_flags(struct page *page)
u |= 1 << KPF_COMPOUND_TAIL;
if (PageHuge(page))
u |= 1 << KPF_HUGE;
- else if (PageTransCompound(page))
+ /*
+ * PageTransCompound can be true for non-huge compound pages (slab
+ * pages or pages allocated by drivers with __GFP_COMP) because it
+ * just checks PG_head/PG_tail, so we need to check PageLRU to make
+ * sure a given page is a thp, not a non-huge compound page.
+ */
+ else if (PageTransCompound(page) && PageLRU(compound_trans_head(page)))
u |= 1 << KPF_THP;
/*
--
1.7.11.4
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages
2012-09-26 20:27 [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages Naoya Horiguchi
@ 2012-09-27 1:17 ` David Rientjes
2012-09-27 1:20 ` Fengguang Wu
1 sibling, 0 replies; 3+ messages in thread
From: David Rientjes @ 2012-09-27 1:17 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Wu Fengguang, Andrew Morton, KOSAKI Motohiro, Andi Kleen,
linux-mm, linux-kernel
On Wed, 26 Sep 2012, Naoya Horiguchi wrote:
> diff --git v3.6-rc6.orig/fs/proc/page.c v3.6-rc6/fs/proc/page.c
> index 7fcd0d6..b8730d9 100644
> --- v3.6-rc6.orig/fs/proc/page.c
> +++ v3.6-rc6/fs/proc/page.c
> @@ -115,7 +115,13 @@ u64 stable_page_flags(struct page *page)
> u |= 1 << KPF_COMPOUND_TAIL;
> if (PageHuge(page))
> u |= 1 << KPF_HUGE;
> - else if (PageTransCompound(page))
> + /*
> + * PageTransCompound can be true for non-huge compound pages (slab
> + * pages or pages allocated by drivers with __GFP_COMP) because it
> + * just checks PG_head/PG_tail, so we need to check PageLRU to make
> + * sure a given page is a thp, not a non-huge compound page.
> + */
> + else if (PageTransCompound(page) && PageLRU(compound_trans_head(page)))
> u |= 1 << KPF_THP;
>
> /*
Yes, that looks good. Nice catch by Fengguang.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages
2012-09-26 20:27 [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages Naoya Horiguchi
2012-09-27 1:17 ` David Rientjes
@ 2012-09-27 1:20 ` Fengguang Wu
1 sibling, 0 replies; 3+ messages in thread
From: Fengguang Wu @ 2012-09-27 1:20 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, KOSAKI Motohiro, David Rientjes, Andi Kleen,
linux-mm, linux-kernel
> - else if (PageTransCompound(page))
> + /*
> + * PageTransCompound can be true for non-huge compound pages (slab
> + * pages or pages allocated by drivers with __GFP_COMP) because it
> + * just checks PG_head/PG_tail, so we need to check PageLRU to make
> + * sure a given page is a thp, not a non-huge compound page.
> + */
> + else if (PageTransCompound(page) && PageLRU(compound_trans_head(page)))
> u |= 1 << KPF_THP;
Reviewed-by: Fengguang Wu <fengguang.wu@intel.com>
Thanks!
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-09-26 20:27 [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages Naoya Horiguchi
2012-09-27 1:17 ` David Rientjes
2012-09-27 1:20 ` Fengguang Wu
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