From 966cca029f739716fbcc8068b8c6dfe381f86fc3 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Mon, 9 Aug 2010 17:20:09 -0700 Subject: [PATCH] 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 Cc: Rafael J. Wysocki Reported-by: Ondreg Zary Tested-by: Ondreg Zary Tested-by: Andrea Gelmini Acked-by: Hugh Dickins Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 6 ++++-- 1 file 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);