linux-kernel - [PATCH] mm: avoid livelock on !__GFP

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Date:	Mon, 24 Oct 2011 23:39:49 -0700
From:	Colin Cross <ccross@...roid.com>
To:	linux-kernel@...r.kernel.org
Cc:	Colin Cross <ccross@...roid.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org
Subject: [PATCH] mm: avoid livelock on !__GFP_FS allocations

Under the following conditions, __alloc_pages_slowpath can loop
forever:
gfp_mask & __GFP_WAIT is true
gfp_mask & __GFP_FS is false
reclaim and compaction make no progress
order <= PAGE_ALLOC_COSTLY_ORDER

These conditions happen very often during suspend and resume,
when pm_restrict_gfp_mask() effectively converts all GFP_KERNEL
allocations into __GFP_WAIT.

The oom killer is not run because gfp_mask & __GFP_FS is false,
but should_alloc_retry will always return true when order is less
than PAGE_ALLOC_COSTLY_ORDER.

Fix __alloc_pages_slowpath to skip retrying when oom killer is
not allowed by the GFP flags, the same way it would skip if the
oom killer was allowed but disabled.

Signed-off-by: Colin Cross <ccross@...roid.com>
---

An alternative patch would add a did_some_progress argument to
__alloc_pages_may_oom, and remove the checks in
__alloc_pages_slowpath that require knowledge of when
__alloc_pages_may_oom chooses to run out_of_memory. If
did_some_progress was still zero, it would goto nopage whether
or not __alloc_pages_may_oom was actually called.

 mm/page_alloc.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fef8dc3..dcd99b3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2193,6 +2193,10 @@ rebalance:
 			}

 			goto restart;
+		} else {
+			/* If we aren't going to try the OOM killer, give up */
+			if (!(gfp_mask & __GFP_NOFAIL))
+				goto nopage;
 		}
 	}

-- 
1.7.4.1

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