linux-kernel - [PATCH] mm/slab: simplify SLAB

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Message-ID: <20250117113226.3484784-1-kevin.brodsky@arm.com>
Date: Fri, 17 Jan 2025 11:32:26 +0000
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH] mm/slab: simplify SLAB_* flag handling

SLUB is the only remaining allocator. We can therefore get rid of
the logic for allocator-specific flags:

* Merge SLAB_CACHE_FLAGS into SLAB_CORE_FLAGS.

* Remove SLAB_FLAGS_PERMITTED (effectively the same as
  CACHE_CREATE_MASK aside from debug flags being unconditionally
  included).

While at it also remove misleading comments that suggest that
multiple allocators are available.

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Hyeonggon Yoo <42.hyeyoo@...il.com>
---
 mm/slab.h        | 28 +++++-----------------------
 mm/slab_common.c | 12 ------------
 2 files changed, 5 insertions(+), 35 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 632fedd71fea..392f4763dee8 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -457,10 +457,12 @@ static inline bool is_kmalloc_normal(struct kmem_cache *s)
 	return !(s->flags & (SLAB_CACHE_DMA|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT));
 }
 
-/* Legal flag mask for kmem_cache_create(), for various configurations */
 #define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | \
 			 SLAB_CACHE_DMA32 | SLAB_PANIC | \
-			 SLAB_TYPESAFE_BY_RCU | SLAB_DEBUG_OBJECTS )
+			 SLAB_TYPESAFE_BY_RCU | SLAB_DEBUG_OBJECTS | \
+			 SLAB_NOLEAKTRACE | SLAB_RECLAIM_ACCOUNT | \
+			 SLAB_TEMPORARY | SLAB_ACCOUNT | \
+			 SLAB_NO_USER_FLAGS | SLAB_KMALLOC | SLAB_NO_MERGE)
 
 #ifdef CONFIG_SLUB_DEBUG
 #define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
@@ -469,27 +471,7 @@ static inline bool is_kmalloc_normal(struct kmem_cache *s)
 #define SLAB_DEBUG_FLAGS (0)
 #endif
 
-#define SLAB_CACHE_FLAGS (SLAB_NOLEAKTRACE | SLAB_RECLAIM_ACCOUNT | \
-			  SLAB_TEMPORARY | SLAB_ACCOUNT | \
-			  SLAB_NO_USER_FLAGS | SLAB_KMALLOC | SLAB_NO_MERGE)
-
-/* Common flags available with current configuration */
-#define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS | SLAB_CACHE_FLAGS)
-
-/* Common flags permitted for kmem_cache_create */
-#define SLAB_FLAGS_PERMITTED (SLAB_CORE_FLAGS | \
-			      SLAB_RED_ZONE | \
-			      SLAB_POISON | \
-			      SLAB_STORE_USER | \
-			      SLAB_TRACE | \
-			      SLAB_CONSISTENCY_CHECKS | \
-			      SLAB_NOLEAKTRACE | \
-			      SLAB_RECLAIM_ACCOUNT | \
-			      SLAB_TEMPORARY | \
-			      SLAB_ACCOUNT | \
-			      SLAB_KMALLOC | \
-			      SLAB_NO_MERGE | \
-			      SLAB_NO_USER_FLAGS)
+#define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS)
 
 bool __kmem_cache_empty(struct kmem_cache *);
 int __kmem_cache_shutdown(struct kmem_cache *);
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a29457bef626..3b07cdaac3ae 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -305,18 +305,6 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
 		goto out_unlock;
 	}
 
-	/* Refuse requests with allocator specific flags */
-	if (flags & ~SLAB_FLAGS_PERMITTED) {
-		err = -EINVAL;
-		goto out_unlock;
-	}
-
-	/*
-	 * Some allocators will constraint the set of valid flags to a subset
-	 * of all flags. We expect them to define CACHE_CREATE_MASK in this
-	 * case, and we'll just provide them with a sanitized version of the
-	 * passed flags.
-	 */
 	flags &= CACHE_CREATE_MASK;
 
 	/* Fail closed on bad usersize of useroffset values. */

base-commit: 9bffa1ad25b8b3b95d8f463e5c24dabe3c87d54d
-- 
2.47.0