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kpageflags: fix wrong KPF_THP on non-huge compound pages

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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.

Signed-off-by: Naoya Horiguchi <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Acked-by: David Rientjes <[email protected]>
Reviewed-by: Fengguang Wu <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Naoya Horiguchi 2012-10-08 16:33:47 -07:00 • committed by Linus Torvalds
commit 7a71932d56
1 changed files with 7 additions and 1 deletions
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8
fs/proc/page.c
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@ -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;
/*