diff options
Diffstat (limited to 'include/linux/mm_types.h')
| -rw-r--r-- | include/linux/mm_types.h | 239 |
1 files changed, 113 insertions, 126 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 21612347d3118..99ce070e7dcb4 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -33,29 +33,27 @@ struct hmm; * it to keep track of whatever it is we are using the page for at the * 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. If you allocate the page using alloc_pages(), you - * can use some of the space in struct page for your own purposes. + * who is mapping it. * - * Pages that were once in the page cache may be found under the RCU lock - * even after they have been recycled to a different purpose. The page - * cache reads and writes some of the fields in struct page to pin the - * page before checking that it's still in the page cache. It is vital - * that all users of struct page: - * 1. Use the first word as PageFlags. - * 2. Clear or preserve bit 0 of page->compound_head. It is used as - * PageTail for compound pages, and the page cache must not see false - * positives. Some users put a pointer here (guaranteed to be at least - * 4-byte aligned), other users avoid using the field altogether. - * 3. page->_refcount must either not be used, or must be used in such a - * way that other CPUs temporarily incrementing and then decrementing the - * refcount does not cause problems. On receiving the page from - * alloc_pages(), the refcount will be positive. - * 4. Either preserve page->_mapcount or restore it to -1 before freeing it. + * If you allocate the page using alloc_pages(), you can use some of the + * space in struct page for your own purposes. The five words in the main + * union are available, except for bit 0 of the first word which must be + * kept clear. Many users use this word to store a pointer to an object + * which is guaranteed to be aligned. If you use the same storage as + * page->mapping, you must restore it to NULL before freeing the page. * - * If you allocate pages of order > 0, you can use the fields in the struct - * page associated with each page, but bear in mind that the pages may have - * been inserted individually into the page cache, so you must use the above - * four fields in a compatible way for each struct page. + * If your page will not be mapped to userspace, you can also use the four + * bytes in the mapcount union, but you must call page_mapcount_reset() + * before freeing it. + * + * If you want to use the refcount field, it must be used in such a way + * that other CPUs temporarily incrementing and then decrementing the + * refcount does not cause problems. On receiving the page from + * alloc_pages(), the refcount will be positive. + * + * If you allocate pages of order > 0, you can use some of the fields + * in each subpage, but you may need to restore some of their values + * afterwards. * * SLUB uses cmpxchg_double() to atomically update its freelist and * counters. That requires that freelist & counters be adjacent and @@ -65,135 +63,122 @@ struct hmm; */ #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE #define _struct_page_alignment __aligned(2 * sizeof(unsigned long)) -#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) -#define _slub_counter_t unsigned long #else -#define _slub_counter_t unsigned int -#endif -#else /* !CONFIG_HAVE_ALIGNED_STRUCT_PAGE */ #define _struct_page_alignment -#define _slub_counter_t unsigned int -#endif /* !CONFIG_HAVE_ALIGNED_STRUCT_PAGE */ +#endif struct page { - /* First double word block */ unsigned long flags; /* Atomic flags, some possibly * updated asynchronously */ - union { - /* See page-flags.h for the definition of PAGE_MAPPING_FLAGS */ - struct address_space *mapping; - - void *s_mem; /* slab first object */ - atomic_t compound_mapcount; /* first tail page */ - /* page_deferred_list().next -- second tail page */ - }; - - /* Second double word */ - union { - pgoff_t index; /* Our offset within mapping. */ - void *freelist; /* sl[aou]b first free object */ - /* page_deferred_list().prev -- second tail page */ - }; - - union { - _slub_counter_t counters; - unsigned int active; /* SLAB */ - struct { /* SLUB */ - unsigned inuse:16; - unsigned objects:15; - unsigned frozen:1; - }; - int units; /* SLOB */ - - struct { /* Page cache */ - /* - * Count of ptes mapped in mms, to show when - * page is mapped & limit reverse map searches. - * - * Extra information about page type may be - * stored here for pages that are never mapped, - * in which case the value MUST BE <= -2. - * See page-flags.h for more details. - */ - atomic_t _mapcount; - - /* - * Usage count, *USE WRAPPER FUNCTION* when manual - * accounting. See page_ref.h - */ - atomic_t _refcount; - }; - }; - /* - * WARNING: bit 0 of the first word encode PageTail(). That means - * the rest users of the storage space MUST NOT use the bit to + * Five words (20/40 bytes) are available in this union. + * WARNING: bit 0 of the first word is used for PageTail(). That + * means the other users of this union MUST NOT use the bit to * avoid collision and false-positive PageTail(). */ union { - struct list_head lru; /* Pageout list, eg. active_list - * protected by zone_lru_lock ! - * Can be used as a generic list - * by the page owner. - */ - struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an - * lru or handled by a slab - * allocator, this points to the - * hosting device page map. - */ - struct { /* slub per cpu partial pages */ - struct page *next; /* Next partial slab */ + struct { /* Page cache and anonymous pages */ + /** + * @lru: Pageout list, eg. active_list protected by + * zone_lru_lock. Sometimes used as a generic list + * by the page owner. + */ + struct list_head lru; + /* See page-flags.h for PAGE_MAPPING_FLAGS */ + struct address_space *mapping; + pgoff_t index; /* Our offset within mapping. */ + /** + * @private: Mapping-private opaque data. + * Usually used for buffer_heads if PagePrivate. + * Used for swp_entry_t if PageSwapCache. + * Indicates order in the buddy system if PageBuddy. + */ + unsigned long private; + }; + struct { /* slab, slob and slub */ + union { + struct list_head slab_list; /* uses lru */ + struct { /* Partial pages */ + struct page *next; #ifdef CONFIG_64BIT - int pages; /* Nr of partial slabs left */ - int pobjects; /* Approximate # of objects */ + int pages; /* Nr of pages left */ + int pobjects; /* Approximate count */ #else - short int pages; - short int pobjects; + short int pages; + short int pobjects; #endif + }; + }; + struct kmem_cache *slab_cache; /* not slob */ + /* Double-word boundary */ + void *freelist; /* first free object */ + union { + void *s_mem; /* slab: first object */ + unsigned long counters; /* SLUB */ + struct { /* SLUB */ + unsigned inuse:16; + unsigned objects:15; + unsigned frozen:1; + }; + }; }; - - struct rcu_head rcu_head; /* Used by SLAB - * when destroying via RCU - */ - /* Tail pages of compound page */ - struct { - unsigned long compound_head; /* If bit zero is set */ + struct { /* Tail pages of compound page */ + unsigned long compound_head; /* Bit zero is set */ /* First tail page only */ unsigned char compound_dtor; unsigned char compound_order; - /* two/six bytes available here */ + atomic_t compound_mapcount; }; - -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS - struct { - unsigned long __pad; /* do not overlay pmd_huge_pte - * with compound_head to avoid - * possible bit 0 collision. - */ - pgtable_t pmd_huge_pte; /* protected by page->ptl */ + struct { /* Second tail page of compound page */ + unsigned long _compound_pad_1; /* compound_head */ + unsigned long _compound_pad_2; + struct list_head deferred_list; }; + struct { /* Page table pages */ + unsigned long _pt_pad_1; /* compound_head */ + pgtable_t pmd_huge_pte; /* protected by page->ptl */ + unsigned long _pt_pad_2; /* mapping */ + struct mm_struct *pt_mm; /* x86 pgds only */ +#if ALLOC_SPLIT_PTLOCKS + spinlock_t *ptl; +#else + spinlock_t ptl; #endif + }; + struct { /* ZONE_DEVICE pages */ + /** @pgmap: Points to the hosting device page map. */ + struct dev_pagemap *pgmap; + unsigned long hmm_data; + unsigned long _zd_pad_1; /* uses mapping */ + }; + + /** @rcu_head: You can use this to free a page by RCU. */ + struct rcu_head rcu_head; }; - union { + union { /* This union is 4 bytes in size. */ /* - * Mapping-private opaque data: - * Usually used for buffer_heads if PagePrivate - * Used for swp_entry_t if PageSwapCache - * Indicates order in the buddy system if PageBuddy + * If the page can be mapped to userspace, encodes the number + * of times this page is referenced by a page table. */ - unsigned long private; -#if USE_SPLIT_PTE_PTLOCKS -#if ALLOC_SPLIT_PTLOCKS - spinlock_t *ptl; -#else - spinlock_t ptl; -#endif -#endif - struct kmem_cache *slab_cache; /* SL[AU]B: Pointer to slab */ + atomic_t _mapcount; + + /* + * If the page is neither PageSlab nor mappable to userspace, + * the value stored here may help determine what this page + * is used for. See page-flags.h for a list of page types + * which are currently stored here. + */ + unsigned int page_type; + + unsigned int active; /* SLAB */ + int units; /* SLOB */ }; + /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */ + atomic_t _refcount; + #ifdef CONFIG_MEMCG struct mem_cgroup *mem_cgroup; #endif @@ -413,6 +398,8 @@ struct mm_struct { unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE & ~VM_STACK */ unsigned long stack_vm; /* VM_STACK */ unsigned long def_flags; + + spinlock_t arg_lock; /* protect the below fields */ unsigned long start_code, end_code, start_data, end_data; unsigned long start_brk, brk, start_stack; unsigned long arg_start, arg_end, env_start, env_end; @@ -627,9 +614,9 @@ struct vm_special_mapping { * If non-NULL, then this is called to resolve page faults * on the special mapping. If used, .pages is not checked. */ - int (*fault)(const struct vm_special_mapping *sm, - struct vm_area_struct *vma, - struct vm_fault *vmf); + vm_fault_t (*fault)(const struct vm_special_mapping *sm, + struct vm_area_struct *vma, + struct vm_fault *vmf); int (*mremap)(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma); |