diff options
| author | Nick Piggin <npiggin@suse.de> | 2007-10-16 01:24:42 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-16 09:42:53 -0700 |
| commit | b55ed816235cf41c29159d22a4cdeec7deb5821c (patch) | |
| tree | 73245c1da2c5352c526d4d25f02e69943b4b0b15 | |
| parent | 45726cb43d11b288c58243a26010f397054222f0 (diff) | |
mm: clarify __add_to_swap_cache locking
__add_to_swap_cache unconditionally sets the page locked, which can be a bit
alarming to the unsuspecting reader: in the code paths where the page is
visible to other CPUs, the page should be (and is) already locked.
Instead, just add a check to ensure the page is locked here, and teach the one
path relying on the old behaviour to call SetPageLocked itself.
[hugh@veritas.com: locking fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/swap_state.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c index 67daecb6031..b52635601df 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -74,6 +74,7 @@ static int __add_to_swap_cache(struct page *page, swp_entry_t entry, { int error; + BUG_ON(!PageLocked(page)); BUG_ON(PageSwapCache(page)); BUG_ON(PagePrivate(page)); error = radix_tree_preload(gfp_mask); @@ -83,7 +84,6 @@ static int __add_to_swap_cache(struct page *page, swp_entry_t entry, entry.val, page); if (!error) { page_cache_get(page); - SetPageLocked(page); SetPageSwapCache(page); set_page_private(page, entry.val); total_swapcache_pages++; @@ -99,15 +99,18 @@ static int add_to_swap_cache(struct page *page, swp_entry_t entry) { int error; + BUG_ON(PageLocked(page)); if (!swap_duplicate(entry)) { INC_CACHE_INFO(noent_race); return -ENOENT; } + SetPageLocked(page); error = __add_to_swap_cache(page, entry, GFP_KERNEL); /* * Anon pages are already on the LRU, we don't run lru_cache_add here. */ if (error) { + ClearPageLocked(page); swap_free(entry); if (error == -EEXIST) INC_CACHE_INFO(exist_race); |