linux-kernel - [PATCH v3 02/21] slab: add SLAB_CONSISTENCY_CHECKS to SLAB_NEVER

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Message-Id: <20260116-sheaves-for-all-v3-2-5595cb000772@suse.cz>
Date: Fri, 16 Jan 2026 15:40:22 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Harry Yoo <harry.yoo@...cle.com>, Petr Tesarik <ptesarik@...e.com>, 
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Hao Li <hao.li@...ux.dev>, Andrew Morton <akpm@...ux-foundation.org>, 
 Uladzislau Rezki <urezki@...il.com>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Suren Baghdasaryan <surenb@...gle.com>, 
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
 Alexei Starovoitov <ast@...nel.org>, linux-mm@...ck.org, 
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev, 
 bpf@...r.kernel.org, kasan-dev@...glegroups.com, 
 Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v3 02/21] slab: add SLAB_CONSISTENCY_CHECKS to
 SLAB_NEVER_MERGE

All the debug flags prevent merging, except SLAB_CONSISTENCY_CHECKS. This
is suboptimal because this flag (like any debug flags) prevents the
usage of any fastpaths, and thus affect performance of any aliased
cache. Also the objects from an aliased cache than the one specified for
debugging could also interfere with the debugging efforts.

Fix this by adding the whole SLAB_DEBUG_FLAGS collection to
SLAB_NEVER_MERGE instead of individual debug flags, so it now also
includes SLAB_CONSISTENCY_CHECKS.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slab_common.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index ee994ec7f251..e691ede0e6a8 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -45,9 +45,8 @@ struct kmem_cache *kmem_cache;
 /*
  * Set of flags that will prevent slab merging
  */
-#define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
-		SLAB_TRACE | SLAB_TYPESAFE_BY_RCU | SLAB_NOLEAKTRACE | \
-		SLAB_FAILSLAB | SLAB_NO_MERGE)
+#define SLAB_NEVER_MERGE (SLAB_DEBUG_FLAGS | SLAB_TYPESAFE_BY_RCU | \
+		SLAB_NOLEAKTRACE | SLAB_FAILSLAB | SLAB_NO_MERGE)

 #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
 			 SLAB_CACHE_DMA32 | SLAB_ACCOUNT)

-- 
2.52.0