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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-08-09 17:20:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-09 20:45:04 -0700
commit966cca029f739716fbcc8068b8c6dfe381f86fc3 (patch)
tree838686762076c262c425e3dc09d0cda4e9e5e83d /mm
parent979f867191f80e74713394cf8c0a3c1b3662b648 (diff)
mm: fix corruption of hibernation caused by reusing swap during image saving
Since 2.6.31, swap_map[]'s refcounting was changed to show that a used swap entry is just for swap-cache, can be reused. Then, while scanning free entry in swap_map[], a swap entry may be able to be reclaimed and reused. It was caused by commit c9e444103b5e7a5 ("mm: reuse unused swap entry if necessary"). But this caused deta corruption at resume. The scenario is - Assume a clean-swap cache, but mapped. - at hibernation_snapshot[], clean-swap-cache is saved as clean-swap-cache and swap_map[] is marked as SWAP_HAS_CACHE. - then, save_image() is called. And reuse SWAP_HAS_CACHE entry to save image, and break the contents. After resume: - the memory reclaim runs and finds clean-not-referenced-swap-cache and discards it because it's marked as clean. But here, the contents on disk and swap-cache is inconsistent. Hance memory is corrupted. This patch avoids the bug by not reclaiming swap-entry during hibernation. This is a quick fix for backporting. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Rafael J. Wysocki <rjw@sisk.pl> Reported-by: Ondreg Zary <linux@rainbow-software.org> Tested-by: Ondreg Zary <linux@rainbow-software.org> Tested-by: Andrea Gelmini <andrea.gelmini@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/swapfile.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 03aa2d55f1a2..f08d165871b3 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -318,8 +318,10 @@ checks:
if (offset > si->highest_bit)
scan_base = offset = si->lowest_bit;
- /* reuse swap entry of cache-only swap if not busy. */
- if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
+ /* reuse swap entry of cache-only swap if not hibernation. */
+ if (vm_swap_full()
+ && usage == SWAP_HAS_CACHE
+ && si->swap_map[offset] == SWAP_HAS_CACHE) {
int swap_was_freed;
spin_unlock(&swap_lock);
swap_was_freed = __try_to_reclaim_swap(si, offset);

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