Commit 9a35de4f authored by Vishal Moola (Oracle)'s avatar Vishal Moola (Oracle) Committed by Andrew Morton
Browse files

pgtable: create struct ptdesc 

Currently, page table information is stored within struct page.  As part
of simplifying struct page, create struct ptdesc for page table
information.

Link: https://lkml.kernel.org/r/20230807230513.102486-3-vishal.moola@gmail.com


Signed-off-by: default avatarVishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: default avatarMike Rapoport (IBM) <rppt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Guo Ren <guoren@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f7bda0d8

include/linux/mm_types.h

+70 −0
Original line number Diff line number Diff line
@@ -397,6 +397,76 @@ FOLIO_MATCH(flags, _flags_2); 
FOLIO_MATCH(compound_head, _head_2);

#undef FOLIO_MATCH



/**

 * struct ptdesc -    Memory descriptor for page tables.

 * @__page_flags:     Same as page flags. Unused for page tables.

 * @pt_rcu_head:      For freeing page table pages.

 * @pt_list:          List of used page tables. Used for s390 and x86.

 * @_pt_pad_1:        Padding that aliases with page's compound head.

 * @pmd_huge_pte:     Protected by ptdesc->ptl, used for THPs.

 * @__page_mapping:   Aliases with page->mapping. Unused for page tables.

 * @pt_mm:            Used for x86 pgds.

 * @pt_frag_refcount: For fragmented page table tracking. Powerpc and s390 only.

 * @_pt_pad_2:        Padding to ensure proper alignment.

 * @ptl:              Lock for the page table.

 * @__page_type:      Same as page->page_type. Unused for page tables.

 * @_refcount:        Same as page refcount. Used for s390 page tables.

 * @pt_memcg_data:    Memcg data. Tracked for page tables here.

 *

 * This struct overlays struct page for now. Do not modify without a good

 * understanding of the issues.

 */

struct ptdesc {

	unsigned long __page_flags;



	union {

		struct rcu_head pt_rcu_head;

		struct list_head pt_list;

		struct {

			unsigned long _pt_pad_1;

			pgtable_t pmd_huge_pte;

		};

	};

	unsigned long __page_mapping;



	union {

		struct mm_struct *pt_mm;

		atomic_t pt_frag_refcount;

	};



	union {

		unsigned long _pt_pad_2;

#if ALLOC_SPLIT_PTLOCKS

		spinlock_t *ptl;

#else

		spinlock_t ptl;

#endif

	};

	unsigned int __page_type;

	atomic_t _refcount;

#ifdef CONFIG_MEMCG

	unsigned long pt_memcg_data;

#endif

};



#define TABLE_MATCH(pg, pt)						\

	static_assert(offsetof(struct page, pg) == offsetof(struct ptdesc, pt))

TABLE_MATCH(flags, __page_flags);

TABLE_MATCH(compound_head, pt_list);

TABLE_MATCH(compound_head, _pt_pad_1);

TABLE_MATCH(pmd_huge_pte, pmd_huge_pte);

TABLE_MATCH(mapping, __page_mapping);

TABLE_MATCH(pt_mm, pt_mm);

TABLE_MATCH(ptl, ptl);

TABLE_MATCH(rcu_head, pt_rcu_head);

TABLE_MATCH(page_type, __page_type);

TABLE_MATCH(_refcount, _refcount);

#ifdef CONFIG_MEMCG

TABLE_MATCH(memcg_data, pt_memcg_data);

#endif

#undef TABLE_MATCH

static_assert(sizeof(struct ptdesc) <= sizeof(struct page));



/*

 * Used for sizing the vmemmap region on some architectures

 */