Commit 07a42788 authored Jun 04, 2014 by Mel Gorman Committed by Linus Torvalds Jun 04, 2014

mm: shmem: avoid atomic operation during shmem_getpage_gfp



shmem_getpage_gfp uses an atomic operation to set the SwapBacked field
before it's even added to the LRU or visible.  This is unnecessary as what
could it possible race against?  Use an unlocked variant.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b745bc85

include/linux/page-flags.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -208,6 +208,7 @@ PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
		PAGEFLAG(SavePinned, savepinned); /* Xen */
		PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
		PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
		__SETPAGEFLAG(SwapBacked, swapbacked)

		__PAGEFLAG(SlobFree, slob_free)

mm/shmem.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1132,7 +1132,7 @@ repeat:
		goto decused;
		}

		SetPageSwapBacked(page);
		__SetPageSwapBacked(page);
		__set_page_locked(page);
		error = mem_cgroup_charge_file(page, current->mm,
		gfp & GFP_RECLAIM_MASK);

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