[PATCH 4.6 08/96] mm, sl[au]b: add __GFP_ATOMIC to the GFP reclaim mask

[Greg Kroah-Hartman]

4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

commit e838a45f9392a5bd2be1cd3ab0b16ae85857461c upstream.

Commit d0164adc89f6 ("mm, page_alloc: distinguish between being unable
to sleep, unwilling to sleep and avoiding waking kswapd") modified
__GFP_WAIT to explicitly identify the difference between atomic callers
and those that were unwilling to sleep.  Later the definition was
removed entirely.

The GFP_RECLAIM_MASK is the set of flags that affect watermark checking
and reclaim behaviour but __GFP_ATOMIC was never added.  Without it,
atomic users of the slab allocator strip the __GFP_ATOMIC flag and
cannot access the page allocator atomic reserves.  This patch addresses
the problem.

The user-visible impact depends on the workload but potentially atomic
allocations unnecessarily fail without this path.

Link: http://lkml.kernel.org/r/20160610093832.GK2527@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reported-by: Marcin Wojtas <mw@xxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/internal.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/internal.h
+++ b/mm/internal.h
@@ -24,7 +24,8 @@
  */
 #define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\
 			__GFP_NOWARN|__GFP_REPEAT|__GFP_NOFAIL|\
-			__GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC)
+			__GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\
+			__GFP_ATOMIC)
 
 /* The GFP flags allowed during early boot */
 #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS))