From: KAMEZAWA Hiroyuki Date: Tue, 10 Aug 2010 00:20:09 +0000 (-0700) Subject: mm: fix corruption of hibernation caused by reusing swap during image saving X-Git-Tag: v2.6.33.8~297 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3eb88cf70fd483e2333b1954e35b355deb5e1f06;p=thirdparty%2Fkernel%2Fstable.git 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 Acked-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- diff --git a/mm/swapfile.c b/mm/swapfile.c index 6c0585b164186..e64e032ee024a 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -315,8 +315,10 @@ 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);