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author | Hugh Dickins <hugh@veritas.com> | 2009-01-06 14:39:36 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-06 15:59:03 -0800 |
commit | a2c43eed8334e878702fca713b212ae2a11d84b9 (patch) | |
tree | 4eb3f9b9153df5e7a638b15a6f7c9aa924066a94 /include/linux/swap.h | |
parent | 7b1fe59793e61f826bef053107b57b23954833bb (diff) | |
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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 'include/linux/swap.h')
-rw-r--r-- | include/linux/swap.h | 10 |
1 files changed, 2 insertions, 8 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h index 366556c..c3ecd47 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -305,8 +305,7 @@ extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t); extern sector_t swapdev_block(int, pgoff_t); extern struct swap_info_struct *get_swap_info_struct(unsigned); extern int reuse_swap_page(struct page *); -extern int remove_exclusive_swap_page(struct page *); -extern int remove_exclusive_swap_page_ref(struct page *); +extern int try_to_free_swap(struct page *); struct backing_dev_info; /* linux/mm/thrash.c */ @@ -388,12 +387,7 @@ static inline void delete_from_swap_cache(struct page *page) #define reuse_swap_page(page) (page_mapcount(page) == 1) -static inline int remove_exclusive_swap_page(struct page *p) -{ - return 0; -} - -static inline int remove_exclusive_swap_page_ref(struct page *page) +static inline int try_to_free_swap(struct page *page) { return 0; } |