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From: Mel Gorman <mgorman@techsingularity.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Marcin Wojtas <mw@semihalf.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Vlastimil Babka <vbabka@suse.cz>
Subject: [PATCH] mm, slaub: Add __GFP_ATOMIC to the GFP reclaim mask
Date: Fri, 10 Jun 2016 10:38:32 +0100
Message-ID: <20160610093832.GK2527@techsingularity.net> (raw)

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.

Cc: <stable@vger.kernel.org> # 4.4+
Reported-by: Marcin Wojtas <mw@semihalf.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/internal.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/internal.h b/mm/internal.h
index a37e5b6f9d25..2524ec880e24 100644
--- 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))

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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-10  9:38 Mel Gorman [this message]
2016-06-10 10:12 ` Vlastimil Babka
2016-06-14  6:36 ` Michal Hocko

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