From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Subject: mm: move _refcount out of struct page union Keeping the refcount in the union only encourages people to put something else in the union which will overlap with _refcount and eventually explode messily. pahole reports no fields change location. Link: http://lkml.kernel.org/r/20180518194519.3820-7-willy@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm_types.h | 25 ++++++++++--------------- 1 file changed, 10 insertions(+), 15 deletions(-) diff -puN include/linux/mm_types.h~mm-move-_refcount-out-of-struct-page-union include/linux/mm_types.h --- a/include/linux/mm_types.h~mm-move-_refcount-out-of-struct-page-union +++ a/include/linux/mm_types.h @@ -113,7 +113,13 @@ struct page { }; }; - union { + union { /* This union is 4 bytes in size. */ + /* + * If the page can be mapped to userspace, encodes the number + * of times this page is referenced by a page table. + */ + atomic_t _mapcount; + /* * If the page is neither PageSlab nor mappable to userspace, * the value stored here may help determine what this page @@ -124,22 +130,11 @@ struct page { unsigned int active; /* SLAB */ int units; /* SLOB */ - - struct { /* Page cache */ - /* - * Count of ptes mapped in mms, to show when - * page is mapped & limit reverse map searches. - */ - atomic_t _mapcount; - - /* - * Usage count, *USE WRAPPER FUNCTION* when manual - * accounting. See page_ref.h - */ - atomic_t _refcount; - }; }; + /* Usage count. *DO NOT USE DIRECTLY*. 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 _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
