mm: Rearrange struct page (fc9bb8c7) · Commits · 戴 / test

include/linux/mm_types.h

+59 −28

Original line number	Diff line number	Diff line
		@@ -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 {
		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.
		*/
		struct { /* SLUB */
		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!
		*/
		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;
		#endif
		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;

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