[PATCH v3 04/21] mm/slab: make caches with sheaves mergeable

[Vlastimil Babka <vbabka@suse.cz>]

Before enabling sheaves for all caches (with automatically determined
capacity), their enablement should no longer prevent merging of caches.
Limit this merge prevention only to caches that were created with a
specific sheaf capacity, by adding the SLAB_NO_MERGE flag to them.

Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slab_common.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index ee245a880603..5c15a4ce5743 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -162,9 +162,6 @@ int slab_unmergeable(struct kmem_cache *s)
 		return 1;
 #endif
 
-	if (s->cpu_sheaves)
-		return 1;
-
 	/*
 	 * We may have set a slab to be unmergeable during bootstrap.
 	 */
@@ -189,9 +186,6 @@ static struct kmem_cache *find_mergeable(unsigned int size, slab_flags_t flags,
 	if (IS_ENABLED(CONFIG_HARDENED_USERCOPY) && args->usersize)
 		return NULL;
 
-	if (args->sheaf_capacity)
-		return NULL;
-
 	flags = kmem_cache_flags(flags, name);
 
 	if (flags & SLAB_NEVER_MERGE)
@@ -336,6 +330,13 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
 	flags &= ~SLAB_DEBUG_FLAGS;
 #endif
 
+	/*
+	 * Caches with specific capacity are special enough. It's simpler to
+	 * make them unmergeable.
+	 */
+	if (args->sheaf_capacity)
+		flags |= SLAB_NO_MERGE;
+
 	mutex_lock(&slab_mutex);
 
 	err = kmem_cache_sanity_check(name, object_size);

-- 
2.52.0