Commit 08df4774 authored Oct 09, 2017 by Paul E. McKenney

mm/ksm: Remove now-redundant smp_read_barrier_depends()

Because READ_ONCE() now implies smp_read_barrier_depends(), the
smp_read_barrier_depends() in get_ksm_page() is now redundant.
This commit removes it and updates the comments.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Cc: <linux-mm@kvack.org>

parent 516df050

mm/ksm.c

+1 −8

Original line number	Diff line number	Diff line
		@@ -675,15 +675,8 @@ static struct page get_ksm_page(struct stable_node stable_node, bool lock_it)
		expected_mapping = (void *)((unsigned long)stable_node \|
		PAGE_MAPPING_KSM);
		again:
		kpfn = READ_ONCE(stable_node->kpfn);
		kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */
		page = pfn_to_page(kpfn);

		/*
		* page is computed from kpfn, so on most architectures reading
		* page->mapping is naturally ordered after reading node->kpfn,
		* but on Alpha we need to be more careful.
		*/
		smp_read_barrier_depends();
		if (READ_ONCE(page->mapping) != expected_mapping)
		goto stale;