path: root/mm/swap_state.c
diff options
authorHugh Dickins <hugh@veritas.com>2009-01-06 14:39:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:59:03 -0800
commita2c43eed8334e878702fca713b212ae2a11d84b9 (patch)
tree4eb3f9b9153df5e7a638b15a6f7c9aa924066a94 /mm/swap_state.c
parent7b1fe59793e61f826bef053107b57b23954833bb (diff)
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 <hugh@veritas.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Rik van Riel <riel@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Robin Holt <holt@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap_state.c')
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
index e793fdea275..bcb47276929 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -195,14 +195,14 @@ void delete_from_swap_cache(struct page *page)
* If we are the only user, then try to free up the swap cache.
* Its ok to check for PageSwapCache without the page lock
- * here because we are going to recheck again inside
- * exclusive_swap_page() _with_ the lock.
+ * here because we are going to recheck again inside
+ * try_to_free_swap() _with_ the lock.
* - Marcelo
static inline void free_swap_cache(struct page *page)
- if (PageSwapCache(page) && trylock_page(page)) {
- remove_exclusive_swap_page(page);
+ if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
+ try_to_free_swap(page);