The patch titled
Subject: mm, swap: Fix memory leak in __read_swap_cache_async()
has been added to the -mm tree. Its filename is
mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled-fix.patch
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------------------------------------------------------
From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm, swap: Fix memory leak in __read_swap_cache_async()
The memory may be leaked in __read_swap_cache_async(). For the cases
as below,
CPU 0 CPU 1
----- -----
find_get_page() == NULL
__swp_swapcount() != 0
new_page = alloc_page_vma()
radix_tree_maybe_preload()
swap in swap slot
swapcache_prepare() == -EEXIST
cond_resched()
reclaim the swap slot
find_get_page() == NULL
__swp_swapcount() == 0
return NULL <- new_page leaked here !!!
The memory leak has been confirmed via checking the value of new_page
when returning inside the loop in __read_swap_cache_async().
This is fixed via replacing return with break inside of loop in
__read_swap_cache_async(), so that there is opportunity for the
new_page to be checked and freed.
Link: http://lkml.kernel.org/r/874lzt6znd.fsf@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reported-by: Hugh Dickins <hughd@xxxxxxxxxx>
Tested-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap_state.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/swap_state.c~mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled-fix mm/swap_state.c
--- a/mm/swap_state.c~mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled-fix
+++ a/mm/swap_state.c
@@ -333,7 +333,7 @@ struct page *__read_swap_cache_async(swp
* else swap_off will be aborted if we return NULL.
*/
if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
- return NULL;
+ break;
/*
* Get a new page to read into from swap.
_
Patches currently in -mm which might be from ying.huang@xxxxxxxxx are
mm-swap-fix-kernel-message-in-swap_info_get.patch
mm-swap-add-cluster-lock.patch
mm-swap-add-cluster-lock-v5.patch
mm-swap-split-swap-cache-into-64mb-trunks.patch
mm-swap-add-cache-for-swap-slots-allocation-fix.patch
mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled.patch
mm-swap-skip-readahead-only-when-swap-slot-cache-is-enabled-fix.patch
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