| From 966cca029f739716fbcc8068b8c6dfe381f86fc3 Mon Sep 17 00:00:00 2001 |
| From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> |
| Date: Mon, 9 Aug 2010 17:20:09 -0700 |
| Subject: mm: fix corruption of hibernation caused by reusing swap during image saving |
| |
| From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> |
| |
| 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> |
| Acked-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> |
| |
| --- |
| mm/swapfile.c | 6 ++++-- |
| 1 file changed, 4 insertions(+), 2 deletions(-) |
| |
| --- 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); |