The patch titled
swap: prevent reuse during hibernation
has been added to the -mm tree. Its filename is
swap-prevent-reuse-during-hibernation.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: swap: prevent reuse during hibernation
From: Hugh Dickins <hughd@xxxxxxxxxx>
Move the hibernation check from scan_swap_map() into try_to_free_swap():
to catch not only the common case when hibernation's allocation itself
triggers swap reuse, but also the less likely case when concurrent page
reclaim (shrink_page_list) might happen to try_to_free_swap from a page.
Hibernation already clears __GFP_IO from the gfp_allowed_mask, to stop
reclaim from going to swap: check that to prevent swap reuse too.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Cc: Ondrej Zary <linux@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Gelmini <andrea.gelmini@xxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Nigel Cunningham <nigel@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff -puN mm/swapfile.c~swap-prevent-reuse-during-hibernation mm/swapfile.c
--- a/mm/swapfile.c~swap-prevent-reuse-during-hibernation
+++ a/mm/swapfile.c
@@ -318,10 +318,8 @@ checks:
if (offset > si->highest_bit)
scan_base = offset = si->lowest_bit;
- /* 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) {
+ /* reuse swap entry of cache-only swap if not busy. */
+ if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
int swap_was_freed;
spin_unlock(&swap_lock);
swap_was_freed = __try_to_reclaim_swap(si, offset);
@@ -688,6 +686,24 @@ int try_to_free_swap(struct page *page)
if (page_swapcount(page))
return 0;
+ /*
+ * Once hibernation has begun to create its image of memory,
+ * there's a danger that one of the calls to try_to_free_swap()
+ * - most probably a call from __try_to_reclaim_swap() while
+ * hibernation is allocating its own swap pages for the image,
+ * but conceivably even a call from memory reclaim - will free
+ * the swap from a page which has already been recorded in the
+ * image as a clean swapcache page, and then reuse its swap for
+ * another page of the image. On waking from hibernation, the
+ * original page might be freed under memory pressure, then
+ * later read back in from swap, now with the wrong data.
+ *
+ * Hibernation clears bits from gfp_allowed_mask to prevent
+ * memory reclaim from writing to disk, so check that here.
+ */
+ if (!(gfp_allowed_mask & __GFP_IO))
+ return 0;
+
delete_from_swap_cache(page);
SetPageDirty(page);
return 1;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
linux-next.patch
mm-fix-swapin-race-condition.patch
swap-revert-special-hibernation-allocation.patch
swap-prevent-reuse-during-hibernation.patch
swap-do-not-send-discards-as-barriers.patch
swap-discard-while-swapping-only-if-swap_flag_discard.patch
mm-compaction-fix-compactpagefailed-counting.patch
ipc-shmc-add-rss-and-swap-size-information-to-proc-sysvipc-shm.patch
ipc-shmc-add-rss-and-swap-size-information-to-proc-sysvipc-shm-v2.patch
prio_tree-debugging-patch.patch
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