From ba9ddf49391645e6bb93219131a40446538a5e76 Mon Sep 17 00:00:00 2001 From: Lee Schermerhorn Date: Sat, 18 Oct 2008 20:26:42 -0700 Subject: Ramfs and Ram Disk pages are unevictable Christoph Lameter pointed out that ram disk pages also clutter the LRU lists. When vmscan finds them dirty and tries to clean them, the ram disk writeback function just redirties the page so that it goes back onto the active list. Round and round she goes... With the ram disk driver [rd.c] replaced by the newer 'brd.c', this is no longer the case, as ram disk pages are no longer maintained on the lru. [This makes them unmigratable for defrag or memory hot remove, but that can be addressed by a separate patch series.] However, the ramfs pages behave like ram disk pages used to, so: Define new address_space flag [shares address_space flags member with mapping's gfp mask] to indicate that the address space contains all unevictable pages. This will provide for efficient testing of ramfs pages in page_evictable(). Also provide wrapper functions to set/test the unevictable state to minimize #ifdefs in ramfs driver and any other users of this facility. Set the unevictable state on address_space structures for new ramfs inodes. Test the unevictable state in page_evictable() to cull unevictable pages. These changes depend on [CONFIG_]UNEVICTABLE_LRU. [riel@redhat.com: undo the brd.c part] Signed-off-by: Lee Schermerhorn Signed-off-by: Rik van Riel Debugged-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/pagemap.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'include/linux/pagemap.h') diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 5da31c12101..09164d2c5c2 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -32,6 +32,28 @@ static inline void mapping_set_error(struct address_space *mapping, int error) } } +#ifdef CONFIG_UNEVICTABLE_LRU +#define AS_UNEVICTABLE (__GFP_BITS_SHIFT + 2) /* e.g., ramdisk, SHM_LOCK */ + +static inline void mapping_set_unevictable(struct address_space *mapping) +{ + set_bit(AS_UNEVICTABLE, &mapping->flags); +} + +static inline int mapping_unevictable(struct address_space *mapping) +{ + if (mapping && (mapping->flags & AS_UNEVICTABLE)) + return 1; + return 0; +} +#else +static inline void mapping_set_unevictable(struct address_space *mapping) { } +static inline int mapping_unevictable(struct address_space *mapping) +{ + return 0; +} +#endif + static inline gfp_t mapping_gfp_mask(struct address_space * mapping) { return (__force gfp_t)mapping->flags & __GFP_BITS_MASK; -- cgit v1.2.3