[PATCH] shrink_list(): skip anon pages if not may_swap
Martin Hicks' page cache reclaim patch added the 'may_swap' flag to the scan_control struct; and modified shrink_list() not to add anon pages to the swap cache if may_swap is not asserted. Ref: http://marc.theaimsgroup.com/?l=linux-mm&m=111461480725322&w=4 However, further down, if the page is mapped, shrink_list() calls try_to_unmap() which will call try_to_unmap_one() via try_to_unmap_anon (). try_to_unmap_one() will BUG_ON() an anon page that is NOT in the swap cache. Martin says he never encountered this path in his testing, but agrees that it might happen. This patch modifies shrink_list() to skip anon pages that are not already in the swap cache when !may_swap, rather than just not adding them to the cache. Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -417,7 +417,9 @@ static int shrink_list(struct list_head *page_list, struct scan_control *sc)
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* Anonymous process memory has backing store?
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* Try to allocate it some swap space here.
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*/
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if (PageAnon(page) && !PageSwapCache(page) && sc->may_swap) {
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if (PageAnon(page) && !PageSwapCache(page)) {
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if (!sc->may_swap)
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goto keep_locked;
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if (!add_to_swap(page))
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goto activate_locked;
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}
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