[PATCH] mm: avoid livelock on !__GFP_FS allocations

From: Colin Cross
Date: Tue Oct 25 2011 - 02:41:10 EST

Under the following conditions, __alloc_pages_slowpath can loop
gfp_mask & __GFP_WAIT is true
gfp_mask & __GFP_FS is false
reclaim and compaction make no progress

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

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@xxxxxxxxxxx>

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;


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