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authorMatthew Wilcox <mawilcox@microsoft.com>2018-06-07 17:08:39 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-07 17:34:37 -0700
commit66a6ffd2af42b0bafaecccbd7c1c30d386de21ab (patch)
treee84faf8badf6ca15db9380b8b743a675156be828 /include
parentb21999da02f891aafa362252f4db7ba5c34a9a8d (diff)
downloadlinux-0-day-66a6ffd2af42b0bafaecccbd7c1c30d386de21ab.tar.gz
linux-0-day-66a6ffd2af42b0bafaecccbd7c1c30d386de21ab.tar.xz
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.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Vlastimil 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mm_types.h66
1 files changed, 33 insertions, 33 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0b0c0e224011b..158f9693f8652 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -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;
};
};