From a2c43eed8334e878702fca713b212ae2a11d84b9 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 6 Jan 2009 14:39:36 -0800 Subject: mm: try_to_free_swap replaces remove_exclusive_swap_page remove_exclusive_swap_page(): its problem is in living up to its name. It doesn't matter if someone else has a reference to the page (raised page_count); it doesn't matter if the page is mapped into userspace (raised page_mapcount - though that hints it may be worth keeping the swap): all that matters is that there be no more references to the swap (and no writeback in progress). swapoff (try_to_unuse) has been removing pages from swapcache for years, with no concern for page count or page mapcount, and we used to have a comment in lookup_swap_cache() recognizing that: if you go for a page of swapcache, you'll get the right page, but it could have been removed from swapcache by the time you get page lock. So, give up asking for exclusivity: get rid of remove_exclusive_swap_page(), and remove_exclusive_swap_page_ref() and remove_exclusive_swap_page_count() which were spawned for the recent LRU work: replace them by the simpler try_to_free_swap() which just checks page_swapcount(). Similarly, remove the page_count limitation from free_swap_and_count(), but assume that it's worth holding on to the swap if page is mapped and swap nowhere near full. Add a vm_swap_full() test in free_swap_cache()? It would be consistent, but I think we probably have enough for now. Signed-off-by: Hugh Dickins Cc: Lee Schermerhorn Cc: Rik van Riel Cc: Nick Piggin Cc: KAMEZAWA Hiroyuki Cc: Robin Holt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swap.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'mm/swap.c') diff --git a/mm/swap.c b/mm/swap.c index ff0b290475fd..ba2c0e8b8b54 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -454,8 +454,7 @@ void pagevec_swap_free(struct pagevec *pvec) struct page *page = pvec->pages[i]; if (PageSwapCache(page) && trylock_page(page)) { - if (PageSwapCache(page)) - remove_exclusive_swap_page_ref(page); + try_to_free_swap(page); unlock_page(page); } } -- cgit v1.2.3-58-ga151