Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 3.13 149/162] mm: free compound page with correct order | Date | Thu, 6 Nov 2014 14:36:53 -0800 |
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3.13.11.11 -stable review patch. If anyone has any objections, please let me know.
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From: Yu Zhao <yuzhao@google.com>
commit 5ddacbe92b806cd5b4f8f154e8e46ac267fff55c upstream.
Compound page should be freed by put_page() or free_pages() with correct order. Not doing so will cause tail pages leaked.
The compound order can be obtained by compound_order() or use HPAGE_PMD_ORDER in our case. Some people would argue the latter is faster but I prefer the former which is more general.
This bug was observed not just on our servers (the worst case we saw is 11G leaked on a 48G machine) but also on our workstations running Ubuntu based distro.
$ cat /proc/vmstat | grep thp_zero_page_alloc thp_zero_page_alloc 55 thp_zero_page_alloc_failed 0
This means there is (thp_zero_page_alloc - 1) * (2M - 4K) memory leaked.
Fixes: 97ae17497e99 ("thp: implement refcounting for huge zero page") Signed-off-by: Yu Zhao <yuzhao@google.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: David Rientjes <rientjes@google.com> Cc: Bob Liu <lliubbo@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- mm/huge_memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 64a7f9c..310f27e 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -193,7 +193,7 @@ retry: preempt_disable(); if (cmpxchg(&huge_zero_page, NULL, zero_page)) { preempt_enable(); - __free_page(zero_page); + __free_pages(zero_page, compound_order(zero_page)); goto retry; } @@ -225,7 +225,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { struct page *zero_page = xchg(&huge_zero_page, NULL); BUG_ON(zero_page == NULL); - __free_page(zero_page); + __free_pages(zero_page, compound_order(zero_page)); return HPAGE_PMD_NR; } -- 1.9.1
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