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author | Hugh Dickins <hughd@google.com> | 2010-09-09 16:38:09 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-09-09 18:57:25 -0700 |
commit | b73d7fcecd93dc15eaa3c45c8c587b613f6673c4 (patch) | |
tree | ebf5a5e10fb246237807317a81f6f40c3eebcd9c /mm | |
parent | 910321ea817a202ff70fac666e37e2c8e2f88823 (diff) | |
download | linux-b73d7fcecd93dc15eaa3c45c8c587b613f6673c4.tar.gz linux-b73d7fcecd93dc15eaa3c45c8c587b613f6673c4.tar.bz2 linux-b73d7fcecd93dc15eaa3c45c8c587b613f6673c4.zip |
swap: prevent reuse during hibernation
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@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Ondrej Zary <linux@rainbow-software.org>
Cc: Andrea Gelmini <andrea.gelmini@gmail.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Nigel Cunningham <nigel@tuxonice.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/swapfile.c | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index f08d165871b3..ed5151079f59 100644 --- a/mm/swapfile.c +++ b/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; |