+ memcg-unify-force-charging-conditions.patch added to -mm tree

+ memcg-unify-force-charging-conditions.patch added to -mm tree

[Andrew Morton]

The patch titled
     Subject: memcg: unify force charging conditions
has been added to the -mm tree.  Its filename is
     memcg-unify-force-charging-conditions.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/memcg-unify-force-charging-conditions.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/memcg-unify-force-charging-conditions.patch

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------------------------------------------------------
From: Shakeel Butt <shakeelb@google.com>
Subject: memcg: unify force charging conditions

Currently the kernel force charges the allocations which have __GFP_HIGH
flag without triggering the memory reclaim.  __GFP_HIGH indicates that the
caller is high priority and since commit 869712fd3de5 ("mm: memcontrol:
fix network errors from failing __GFP_ATOMIC charges") the kernel lets
such allocations do force charging.  Please note that __GFP_ATOMIC has
been replaced by __GFP_HIGH.

__GFP_HIGH does not tell if the caller can block or can trigger reclaim. 
There are separate checks to determine that.  So, there is no need to skip
reclaiming for __GFP_HIGH allocations.  So, handle __GFP_HIGH together
with __GFP_NOFAIL which also does force charging.

Please note that this is a noop change as there are no __GFP_HIGH
allocators in the kernel which also have __GFP_ACCOUNT (or SLAB_ACCOUNT)
and does not allow reclaim for now.

Link: https://lkml.kernel.org/r/20220211064917.2028469-3-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

--- a/mm/memcontrol.c~memcg-unify-force-charging-conditions
+++ a/mm/memcontrol.c
@@ -2566,15 +2566,6 @@ retry:
 	}
 
 	/*
-	 * Memcg doesn't have a dedicated reserve for atomic
-	 * allocations. But like the global atomic pool, we need to
-	 * put the burden of reclaim on regular allocation requests
-	 * and let these go through as privileged allocations.
-	 */
-	if (gfp_mask & __GFP_ATOMIC)
-		goto force;
-
-	/*
 	 * Prevent unbounded recursion when reclaim operations need to
 	 * allocate memory. This might exceed the limits temporarily,
 	 * but we prefer facilitating memory reclaim and getting back
@@ -2647,7 +2638,13 @@ retry:
 		goto retry;
 	}
 nomem:
-	if (!(gfp_mask & __GFP_NOFAIL))
+	/*
+	 * Memcg doesn't have a dedicated reserve for atomic
+	 * allocations. But like the global atomic pool, we need to
+	 * put the burden of reclaim on regular allocation requests
+	 * and let these go through as privileged allocations.
+	 */
+	if (!(gfp_mask & (__GFP_NOFAIL | __GFP_HIGH)))
 		return -ENOMEM;
 force:
 	/*
_

Patches currently in -mm which might be from shakeelb@google.com are

memcg-replace-in_interrupt-with-in_task.patch
memcg-refactor-mem_cgroup_oom.patch
memcg-unify-force-charging-conditions.patch
selftests-memcg-test-high-limit-for-single-entry-allocation.patch
memcg-synchronously-enforce-memoryhigh-for-large-overcharges.patch