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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-08-11 15:32:15 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-13 13:20:26 -0700
commit46dc12d5f11adc21f0071f41d251f3e68869213d (patch)
treecc2fe732ae9b07563b527b4dc4034f5e4125131c
parent8c2b26e45cca45298627428a0bc8bf8a6423d9d1 (diff)
mm: fix corruption of hibernation caused by reusing swap during image saving
commit 966cca029f739716fbcc8068b8c6dfe381f86fc3 upstream. 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> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--mm/swapfile.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 9c590eef7912..270e136349a0 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -330,8 +330,10 @@ 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()
+ && cache == SWAP_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);