From: Yu Zhao <[email protected]>
Subject: mm: free compound page with correct order
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 <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Bob Liu <[email protected]>
Cc: <[email protected]> [3.8+]
Signed-off-by: Andrew Morton <[email protected]>
---
mm/huge_memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN mm/huge_memory.c~mm-free-compound-page-with-correct-order
mm/huge_memory.c
--- a/mm/huge_memory.c~mm-free-compound-page-with-correct-order
+++ a/mm/huge_memory.c
@@ -200,7 +200,7 @@ 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;
}
@@ -232,7 +232,7 @@ static unsigned long shrink_huge_zero_pa
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;
}
_
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