From 46dc12d5f11adc21f0071f41d251f3e68869213d Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Wed, 11 Aug 2010 15:32:15 -0700 Subject: [PATCH] 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 Cc: Rafael J. Wysocki Reported-by: Ondreg Zary Tested-by: Ondreg Zary Tested-by: Andrea Gelmini Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/swapfile.c | 6 ++++-- 1 file 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); -- 2.39.5