diff options
| -rw-r--r-- | include/linux/mm_types.h | 87 |
1 files changed, 59 insertions, 28 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index e5fb2a70518b..3d76a433d52f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -30,24 +30,60 @@ struct address_space; * moment. Note that we have no way to track which tasks are using * a page, though if it is a pagecache page, rmap structures can tell us * who is mapping it. + * + * The objects in struct page are organized in double word blocks in + * order to allows us to use atomic double word operations on portions + * of struct page. That is currently only used by slub but the arrangement + * allows the use of atomic double word operations on the flags/mapping + * and lru list pointers also. */ struct page { + /* First double word block */ unsigned long flags; /* Atomic flags, some possibly * updated asynchronously */ - atomic_t _count; /* Usage count, see below. */ + struct address_space *mapping; /* If low bit clear, points to + * inode address_space, or NULL. + * If page mapped as anonymous + * memory, low bit is set, and + * it points to anon_vma object: + * see PAGE_MAPPING_ANON below. + */ + /* Second double word */ union { - atomic_t _mapcount; /* Count of ptes mapped in mms, - * to show when page is mapped - * & limit reverse map searches. + struct { + pgoff_t index; /* Our offset within mapping. */ + atomic_t _mapcount; /* Count of ptes mapped in mms, + * to show when page is mapped + * & limit reverse map searches. + */ + atomic_t _count; /* Usage count, see below. */ + }; + + struct { /* SLUB cmpxchg_double area */ + void *freelist; + union { + unsigned long counters; + struct { + unsigned inuse:16; + unsigned objects:15; + unsigned frozen:1; + /* + * Kernel may make use of this field even when slub + * uses the rest of the double word! */ - struct { /* SLUB */ - unsigned inuse:16; - unsigned objects:15; - unsigned frozen:1; + atomic_t _count; + }; + }; }; }; + + /* Third double word block */ + struct list_head lru; /* Pageout list, eg. active_list + * protected by zone->lru_lock ! + */ + + /* Remainder is not double word aligned */ union { - struct { unsigned long private; /* Mapping-private opaque data: * usually used for buffer_heads * if PagePrivate set; used for @@ -55,27 +91,13 @@ struct page { * indicates order in the buddy * system if PG_buddy is set. */ - struct address_space *mapping; /* If low bit clear, points to - * inode address_space, or NULL. - * If page mapped as anonymous - * memory, low bit is set, and - * it points to anon_vma object: - * see PAGE_MAPPING_ANON below. - */ - }; #if USE_SPLIT_PTLOCKS - spinlock_t ptl; + spinlock_t ptl; #endif - struct kmem_cache *slab; /* SLUB: Pointer to slab */ - struct page *first_page; /* Compound tail pages */ + struct kmem_cache *slab; /* SLUB: Pointer to slab */ + struct page *first_page; /* Compound tail pages */ }; - union { - pgoff_t index; /* Our offset within mapping. */ - void *freelist; /* SLUB: freelist req. slab lock */ - }; - struct list_head lru; /* Pageout list, eg. active_list - * protected by zone->lru_lock ! - */ + /* * On machines where all RAM is mapped into kernel address space, * we can simply calculate the virtual address. On machines with @@ -101,7 +123,16 @@ struct page { */ void *shadow; #endif -}; +} +/* + * If another subsystem starts using the double word pairing for atomic + * operations on struct page then it must change the #if to ensure + * proper alignment of the page struct. + */ +#if defined(CONFIG_SLUB) && defined(CONFIG_CMPXCHG_LOCAL) + __attribute__((__aligned__(2*sizeof(unsigned long)))) +#endif +; typedef unsigned long __nocast vm_flags_t; |