This is a note to let you know that I've just added the patch titled
mm: free compound page with correct order
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-free-compound-page-with-correct-order.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5ddacbe92b806cd5b4f8f154e8e46ac267fff55c Mon Sep 17 00:00:00 2001
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Date: Wed, 29 Oct 2014 14:50:26 -0700
Subject: mm: free compound page with correct order
From: Yu Zhao <yuzhao@xxxxxxxxxx>
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@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Bob Liu <lliubbo@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -199,7 +199,7 @@ 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;
}
@@ -231,7 +231,7 @@ 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;
}
Patches currently in stable-queue which might be from yuzhao@xxxxxxxxxx are
queue-3.14/mm-free-compound-page-with-correct-order.patch
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