[PATCH 13/17] mm: shmem: Avoid atomic operation during shmem_getpage_gfp

From: Mel Gorman
Date: Thu May 01 2014 - 04:47:48 EST


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@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
include/linux/page-flags.h | 1 +
mm/shmem.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index d1fe1a7..4d4b39a 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -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)

diff --git a/mm/shmem.c b/mm/shmem.c
index 9f70e02..f47fb38 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -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);
--
1.8.4.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/