linux-kernel - [PATCH v2 1/3] mm,slub: Do not special case N_NORMAL nodes for slab

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Message-ID: <20250408084153.255762-2-osalvador@suse.de>
Date: Tue,  8 Apr 2025 10:41:51 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Vlastimil Babka <vbabka@...e.cz>,
	Harry Yoo <harry.yoo@...cle.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	linux-cxl@...r.kernel.org,
	Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v2 1/3] mm,slub: Do not special case N_NORMAL nodes for slab_nodes

Currently, slab_mem_going_going_callback() checks whether the node has
N_NORMAL memory in order to be set in slab_nodes.
While it is true that gettind rid of that enforcing would mean
ending up with movables nodes in slab_nodes, the memory waste that comes
with that is negligible.

So stop checking for status_change_nid_normal and just use status_change_nid
instead which works for both types of memory.

Also, once we allocate the kmem_cache_node cache  for the node in
slab_mem_online_callback(), we never deallocate it in
slab_mem_off_callback() when the node goes memoryless, so we can just
get rid of it.

The only side effect is that we will stop clearing the node from slab_nodes.

Signed-off-by: Oscar Salvador <osalvador@...e.de>
---
 mm/slub.c | 30 +-----------------------------
 1 file changed, 1 insertion(+), 29 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index b46f87662e71..e716b4cb2d0e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -6164,36 +6164,12 @@ static int slab_mem_going_offline_callback(void *arg)
 	return 0;
 }
 
-static void slab_mem_offline_callback(void *arg)
-{
-	struct memory_notify *marg = arg;
-	int offline_node;
-
-	offline_node = marg->status_change_nid_normal;
-
-	/*
-	 * If the node still has available memory. we need kmem_cache_node
-	 * for it yet.
-	 */
-	if (offline_node < 0)
-		return;
-
-	mutex_lock(&slab_mutex);
-	node_clear(offline_node, slab_nodes);
-	/*
-	 * We no longer free kmem_cache_node structures here, as it would be
-	 * racy with all get_node() users, and infeasible to protect them with
-	 * slab_mutex.
-	 */
-	mutex_unlock(&slab_mutex);
-}
-
 static int slab_mem_going_online_callback(void *arg)
 {
 	struct kmem_cache_node *n;
 	struct kmem_cache *s;
 	struct memory_notify *marg = arg;
-	int nid = marg->status_change_nid_normal;
+	int nid = marg->status_change_nid;
 	int ret = 0;
 
 	/*
@@ -6251,10 +6227,6 @@ static int slab_memory_callback(struct notifier_block *self,
 	case MEM_GOING_OFFLINE:
 		ret = slab_mem_going_offline_callback(arg);
 		break;
-	case MEM_OFFLINE:
-	case MEM_CANCEL_ONLINE:
-		slab_mem_offline_callback(arg);
-		break;
 	case MEM_ONLINE:
 	case MEM_CANCEL_OFFLINE:
 		break;
-- 
2.49.0