The patch titled
Subject: Re: pagemap: fix wrong KPF_THP on slab pages
has been added to the -mm tree. Its filename is
pagemap-fix-wrong-kpf_thp-on-slab-pages.patch
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------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: Re: 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.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/page.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN fs/proc/page.c~pagemap-fix-wrong-kpf_thp-on-slab-pages fs/proc/page.c
--- a/fs/proc/page.c~pagemap-fix-wrong-kpf_thp-on-slab-pages
+++ a/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;
/*
_
Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are
pagemap-fix-wrong-kpf_thp-on-slab-pages.patch
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