linux-kernel - [PATCH] mm/slab_common: use SLAB_NO_MERGE instead of negative refcount

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Date:   Tue, 13 Jun 2023 12:28:21 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        patches@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH] mm/slab_common: use SLAB_NO_MERGE instead of negative refcount

When CONFIG_MEMCG_KMEM is enabled, we disable cache merging for
KMALLOC_NORMAL so they don't end up merged with a cache that uses ad-hoc
__GFP_ACCOUNT. This was implemented by setting refcount to -1, but now
we have a proper SLAB_NO_MERGE flag, so use that instead.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slab_common.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 0e0a617eae7d..67caf0bc3194 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -878,17 +878,17 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
 		flags |= SLAB_CACHE_DMA;
 	}
 
-	kmalloc_caches[type][idx] = create_kmalloc_cache(
-					kmalloc_info[idx].name[type],
-					kmalloc_info[idx].size, flags, 0,
-					kmalloc_info[idx].size);
-
 	/*
 	 * If CONFIG_MEMCG_KMEM is enabled, disable cache merging for
 	 * KMALLOC_NORMAL caches.
 	 */
 	if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_NORMAL))
-		kmalloc_caches[type][idx]->refcount = -1;
+		flags |= SLAB_NO_MERGE;
+
+	kmalloc_caches[type][idx] = create_kmalloc_cache(
+					kmalloc_info[idx].name[type],
+					kmalloc_info[idx].size, flags, 0,
+					kmalloc_info[idx].size);
 }
 
 /*
-- 
2.41.0