mm: use READ_ONCE() for non-scalar types

Commit 38c5ce936a08 ("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>

diff --git a/mm/gup.c b/mm/gup.c
index ca7b607..6297f6b 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -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
                 */
-               pte_t pte = ACCESS_ONCE(*ptep);
+               pte_t pte = READ_ONCE(*ptep);
                struct page *page;
 
                /*
@@ -1309,7 +1309,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
        local_irq_save(flags);
        pgdp = pgd_offset(mm, addr);
        do {
-               pgd_t pgd = ACCESS_ONCE(*pgdp);
+               pgd_t pgd = READ_ONCE(*pgdp);
 
                next = pgd_addr_end(addr, end);
                if (pgd_none(pgd))