Commit 66a6ffd2 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds

mm: combine first three unions in struct page

By combining these three one-word unions into one three-word union, we
make it easier for users to add their own multi-word fields to struct
page, as well as making it obvious that SLUB needs to keep its double-word
alignment for its freelist & counters.

No field moves position; verified with pahole.

Link: http://lkml.kernel.org/r/20180518194519.3820-8-willy@infradead.orgSigned-off-by: default avatarMatthew Wilcox <mawilcox@microsoft.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b21999da
......@@ -70,46 +70,46 @@ struct hmm;
#endif
struct page {
/* First double word block */
unsigned long flags; /* Atomic flags, some possibly
* updated asynchronously */
/* Three words (12/24 bytes) are available in this union. */
union {
/* See page-flags.h for the definition of PAGE_MAPPING_FLAGS */
struct address_space *mapping;
struct kmem_cache *slab_cache; /* SL[AU]B: Pointer to slab */
struct { /* Page cache and anonymous pages */
/* 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 */
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;
};
};
};
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 {
/*
* 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;
#if USE_SPLIT_PTE_PTLOCKS
struct list_head deferred_list; /* second tail page */
struct { /* Page table pages */
unsigned long _pt_pad_2; /* mapping */
unsigned long _pt_pad_3;
#if ALLOC_SPLIT_PTLOCKS
spinlock_t *ptl;
spinlock_t *ptl;
#else
spinlock_t ptl;
#endif
spinlock_t ptl;
#endif
void *s_mem; /* slab first object */
unsigned long counters; /* SLUB */
struct { /* SLUB */
unsigned inuse:16;
unsigned objects:15;
unsigned frozen:1;
};
};
......
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