Commit 9d8c47e4 authored Apr 15, 2015 by Jason Low Committed by Linus Torvalds Apr 15, 2015

mm: use READ_ONCE() for non-scalar types



Commit 38c5ce93 ("mm/gup: Replace ACCESS_ONCE with READ_ONCE")
converted ACCESS_ONCE usage in gup_pmd_range() to READ_ONCE, since
ACCESS_ONCE doesn't work reliably on non-scalar types.

This patch also fixes the other ACCESS_ONCE usages in gup_pte_range()
and __get_user_pages_fast() in mm/gup.c

Signed-off-by: Jason Low <jason.low2@hp.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 6cd57613

mm/gup.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1019,7 +1019,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
	*		*
	* for an example see gup_get_pte in arch/x86/mm/gup.c		* for an example see gup_get_pte in arch/x86/mm/gup.c
	*/		*/
	pte_t pte = ACCESS_ONCE(*ptep);		pte_t pte = READ_ONCE(*ptep);
	struct page *page;		struct page *page;

	/*		/*
	@@ -1309,7 +1309,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
	local_irq_save(flags);		local_irq_save(flags);
	pgdp = pgd_offset(mm, addr);		pgdp = pgd_offset(mm, addr);
	do {		do {
	pgd_t pgd = ACCESS_ONCE(*pgdp);		pgd_t pgd = READ_ONCE(*pgdp);

	next = pgd_addr_end(addr, end);		next = pgd_addr_end(addr, end);
	if (pgd_none(pgd))		if (pgd_none(pgd))