Commit 0005d20b authored Mar 16, 2017 by Kirill A. Shutemov Committed by Ingo Molnar Mar 18, 2017

mm/gup: Move page table entry dereference into helper function



This is a preparation patch for the transition of x86 to the generic GUP_fast()
implementation.

On x86 PAE, page table entry is larger than sizeof(long) and we would
need to provide a helper that can read the entry atomically.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aneesh Kumar K . V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dann Frazier <dann.frazier@canonical.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170316152655.37789-4-kirill.shutemov@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent e7884f8e

mm/gup.c

+12 −8

Original line number	Diff line number	Diff line
		@@ -1189,6 +1189,17 @@ struct page *get_dump_page(unsigned long addr)
		*/
		#ifdef CONFIG_HAVE_GENERIC_RCU_GUP

		#ifndef gup_get_pte
		/*
		* We assume that the PTE can be read atomically. If this is not the case for
		* your architecture, please provide the helper.
		*/
		static inline pte_t gup_get_pte(pte_t *ptep)
		{
		return READ_ONCE(*ptep);
		}
		#endif

		#ifdef __HAVE_ARCH_PTE_SPECIAL
		static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
		int write, struct page *pages, int nr)
		@@ -1198,14 +1209,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,

		ptem = ptep = pte_offset_map(&pmd, addr);
		do {
		/*
		* In the line below we are assuming that the pte can be read
		* atomically. If this is not the case for your architecture,
		* please wrap this in a helper function!
		*
		* for an example see gup_get_pte in arch/x86/mm/gup.c
		*/
		pte_t pte = READ_ONCE(*ptep);
		pte_t pte = gup_get_pte(ptep);
		struct page head, page;

		/*