Messages in this thread Patch in this message | | | From | Naoya Horiguchi <> | Subject | [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages | Date | Wed, 26 Sep 2012 16:27:14 -0400 |
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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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