[PATCH v2 1/1] kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument kvfree_rcu()

[Paul E. McKenney]

This commit applies the __GFP_NOMEMALLOC gfp flag to memory allocations
carried out by the single-argument variant of kvfree_rcu(), thus avoiding
this can-sleep code path from dipping into the emergency reserves.

Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/rcu/tree.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e450c17a06b2..e7b705155c92 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3496,11 +3496,14 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
 			// view. Apart of that it forbids any OOM invoking what is
 			// also beneficial since we are about to release memory soon.
 			//
+			// __GFP_NOMEMALLOC - prevents from consuming of all the
+			// memory reserves. Please note we have a fallback path.
+			//
 			// __GFP_NOWARN - it is supposed that an allocation can
 			// be failed under low memory or high memory pressure
 			// scenarios.
 			bnode = (struct kvfree_rcu_bulk_data *)
-				__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+				__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 			*krcp = krc_this_cpu_lock(flags);
 		}
 
-- 
2.20.1
<snip>

Thanks!

--
Vlad Rezki