From 51726b1222863852c46ca21ed0115b85d1edfd89 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 6 Jan 2009 14:39:25 -0800 Subject: mm: replace some BUG_ONs by VM_BUG_ONs The swap code is over-provisioned with BUG_ONs on assorted page flags, mostly dating back to 2.3. They're good documentation, and guard against developer error, but a waste of space on most systems: change them to VM_BUG_ONs, conditional on CONFIG_DEBUG_VM. Just delete the PagePrivate ones: they're later, from 2.5.69, but even less interesting now. Signed-off-by: Hugh Dickins Reviewed-by: Christoph Lameter Cc: Nick Piggin Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swap_state.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) (limited to 'mm/swap_state.c') diff --git a/mm/swap_state.c b/mm/swap_state.c index 3353c9029ce..e793fdea275 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -72,10 +72,10 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) { int error; - BUG_ON(!PageLocked(page)); - BUG_ON(PageSwapCache(page)); - BUG_ON(PagePrivate(page)); - BUG_ON(!PageSwapBacked(page)); + VM_BUG_ON(!PageLocked(page)); + VM_BUG_ON(PageSwapCache(page)); + VM_BUG_ON(!PageSwapBacked(page)); + error = radix_tree_preload(gfp_mask); if (!error) { page_cache_get(page); @@ -108,10 +108,9 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) */ void __delete_from_swap_cache(struct page *page) { - BUG_ON(!PageLocked(page)); - BUG_ON(!PageSwapCache(page)); - BUG_ON(PageWriteback(page)); - BUG_ON(PagePrivate(page)); + VM_BUG_ON(!PageLocked(page)); + VM_BUG_ON(!PageSwapCache(page)); + VM_BUG_ON(PageWriteback(page)); radix_tree_delete(&swapper_space.page_tree, page_private(page)); set_page_private(page, 0); @@ -134,8 +133,8 @@ int add_to_swap(struct page * page, gfp_t gfp_mask) swp_entry_t entry; int err; - BUG_ON(!PageLocked(page)); - BUG_ON(!PageUptodate(page)); + VM_BUG_ON(!PageLocked(page)); + VM_BUG_ON(!PageUptodate(page)); for (;;) { entry = get_swap_page(); -- cgit 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_state.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'mm/swap_state.c') 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); unlock_page(page); } } -- cgit From ac47b003d03c2a4f28aef1d505b66d24ad191c4f Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 6 Jan 2009 14:39:39 -0800 Subject: mm: remove gfp_mask from add_to_swap Remove gfp_mask argument from add_to_swap(): it's misleading because its only caller, shrink_page_list(), is not atomic at that point; and in due course (implementing discard) we'll sometimes want to allocate some memory with GFP_NOIO (as is used in swap_writepage) when allocating swap. No change to the gfp_mask passed down to add_to_swap_cache(): still use __GFP_HIGH without __GFP_WAIT (with nomemalloc and nowarn as before): though it's not obvious if that's the best combination to ask for here. 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_state.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/swap_state.c') diff --git a/mm/swap_state.c b/mm/swap_state.c index bcb47276929..81c825f67a7 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -128,7 +128,7 @@ void __delete_from_swap_cache(struct page *page) * Allocate swap space for the page and add the page to the * swap cache. Caller needs to hold the page lock. */ -int add_to_swap(struct page * page, gfp_t gfp_mask) +int add_to_swap(struct page *page) { swp_entry_t entry; int err; @@ -153,7 +153,7 @@ int add_to_swap(struct page * page, gfp_t gfp_mask) * Add it to the swap cache and mark it dirty */ err = add_to_swap_cache(page, entry, - gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN); + __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); switch (err) { case 0: /* Success */ -- cgit