+ mm-memcg-move-generation-assignment-and-comparison-together.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/memcg: move generation assignment and comparison together
has been added to the -mm tree.  Its filename is
     mm-memcg-move-generation-assignment-and-comparison-together.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-move-generation-assignment-and-comparison-together.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-move-generation-assignment-and-comparison-together.patch

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------------------------------------------------------
From: Wei Yang <richard.weiyang@gmail.com>
Subject: mm/memcg: move generation assignment and comparison together

For each round-trip, we assign generation on first invocation and compare
it on subsequent invocations.

Let's move them together to make it more self-explaining.  Also this
reduces a check on prev.

Link: https://lkml.kernel.org/r/20220225003437.12620-4-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-move-generation-assignment-and-comparison-together
+++ a/mm/memcontrol.c
@@ -1045,7 +1045,14 @@ struct mem_cgroup *mem_cgroup_iter(struc
 		mz = root->nodeinfo[reclaim->pgdat->node_id];
 		iter = &mz->iter;
 
-		if (prev && reclaim->generation != iter->generation)
+		/*
+		 * On first invocation, assign iter->generation to
+		 * reclaim->generation.
+		 * On subsequent invocations, make sure no one else jump in.
+		 */
+		if (!prev)
+			reclaim->generation = iter->generation;
+		else if (reclaim->generation != iter->generation)
 			goto out_unlock;
 
 		while (1) {
@@ -1105,8 +1112,6 @@ struct mem_cgroup *mem_cgroup_iter(struc
 
 		if (!memcg)
 			iter->generation++;
-		else if (!prev)
-			reclaim->generation = iter->generation;
 	}
 
 out_unlock:
_

Patches currently in -mm which might be from richard.weiyang@gmail.com are

mm-memcg-mem_cgroup_per_node-is-already-set-to-0-on-allocation.patch
mm-memcg-retrieve-parent-memcg-from-cssparent.patch
mm-memcg-set-memcg-after-css-verified-and-got-reference.patch
mm-memcg-set-pos-to-prev-unconditionally.patch
mm-memcg-move-generation-assignment-and-comparison-together.patch
mm-page_alloc-add-same-penalty-is-enough-to-get-round-robin-order.patch
mm-page_alloc-add-penalty-to-local_node.patch
memcg-do-not-tweak-node-in-alloc_mem_cgroup_per_node_info.patch