[PATCH RFC v2 07/20] slab: handle kmalloc sheaves bootstrap

[Vlastimil Babka <vbabka@suse.cz>]

Enable sheaves for kmalloc caches. For other types than KMALLOC_NORMAL,
we can simply allow them in calculate_sizes() as they are created later
than KMALLOC_NORMAL caches and can allocate sheaves and barns from
those.

For KMALLOC_NORMAL caches we perform additional step after first
creating them without sheaves. Then bootstrap_cache_sheaves() simply
allocates and initializes barns and sheaves and finally sets
s->sheaf_capacity to make them actually used.

Afterwards the only caches left without sheaves (unless SLUB_TINY or
debugging is enabled) are kmem_cache and kmem_cache_node. These are only
used when creating or destroying other kmem_caches. Thus they are not
performance critical and we can simply leave it that way.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 84 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 0177a654a06a..f2de44f8bda4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2593,7 +2593,8 @@ static void *setup_object(struct kmem_cache *s, void *object)
 	return object;
 }
 
-static struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp)
+static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
+					      unsigned int capacity)
 {
 	struct slab_sheaf *sheaf;
 	size_t sheaf_size;
@@ -2611,7 +2612,7 @@ static struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp)
 	if (s->flags & SLAB_KMALLOC)
 		gfp |= __GFP_NO_OBJ_EXT;
 
-	sheaf_size = struct_size(sheaf, objects, s->sheaf_capacity);
+	sheaf_size = struct_size(sheaf, objects, capacity);
 	sheaf = kzalloc(sheaf_size, gfp);
 
 	if (unlikely(!sheaf))
@@ -2624,6 +2625,12 @@ static struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp)
 	return sheaf;
 }
 
+static inline struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s,
+						   gfp_t gfp)
+{
+	return __alloc_empty_sheaf(s, gfp, s->sheaf_capacity);
+}
+
 static void free_empty_sheaf(struct kmem_cache *s, struct slab_sheaf *sheaf)
 {
 	kfree(sheaf);
@@ -8117,8 +8124,11 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s)
 	if (s->flags & SLAB_RECLAIM_ACCOUNT)
 		s->allocflags |= __GFP_RECLAIMABLE;
 
-	/* kmalloc caches need extra care to support sheaves */
-	if (!is_kmalloc_cache(s))
+	/*
+	 * For KMALLOC_NORMAL caches we enable sheaves later by
+	 * bootstrap_kmalloc_sheaves() to avoid recursion
+	 */
+	if (!is_kmalloc_normal(s))
 		s->sheaf_capacity = calculate_sheaf_capacity(s, args);
 
 	/*
@@ -8613,6 +8623,74 @@ static struct kmem_cache * __init bootstrap(struct kmem_cache *static_cache)
 	return s;
 }
 
+/*
+ * Finish the sheaves initialization done normally by init_percpu_sheaves() and
+ * init_kmem_cache_nodes(). For normal kmalloc caches we have to bootstrap it
+ * since sheaves and barns are allocated by kmalloc.
+ */
+static void __init bootstrap_cache_sheaves(struct kmem_cache *s)
+{
+	struct kmem_cache_args empty_args = {};
+	unsigned int capacity;
+	bool failed = false;
+	int node, cpu;
+
+	capacity = calculate_sheaf_capacity(s, &empty_args);
+
+	/* capacity can be 0 due to debugging or SLUB_TINY */
+	if (!capacity)
+		return;
+
+	for_each_node_mask(node, slab_nodes) {
+		struct node_barn *barn;
+
+		barn = kmalloc_node(sizeof(*barn), GFP_KERNEL, node);
+
+		if (!barn) {
+			failed = true;
+			goto out;
+		}
+
+		barn_init(barn);
+		get_node(s, node)->barn = barn;
+	}
+
+	for_each_possible_cpu(cpu) {
+		struct slub_percpu_sheaves *pcs;
+
+		pcs = per_cpu_ptr(s->cpu_sheaves, cpu);
+
+		pcs->main = __alloc_empty_sheaf(s, GFP_KERNEL, capacity);
+
+		if (!pcs->main) {
+			failed = true;
+			break;
+		}
+	}
+
+out:
+	/*
+	 * It's still early in boot so treat this like same as a failure to
+	 * create the kmalloc cache in the first place
+	 */
+	if (failed)
+		panic("Out of memory when creating kmem_cache %s\n", s->name);
+
+	s->sheaf_capacity = capacity;
+}
+
+static void __init bootstrap_kmalloc_sheaves(void)
+{
+	enum kmalloc_cache_type type;
+
+	for (type = KMALLOC_NORMAL; type <= KMALLOC_RANDOM_END; type++) {
+		for (int idx = 0; idx < KMALLOC_SHIFT_HIGH + 1; idx++) {
+			if (kmalloc_caches[type][idx])
+				bootstrap_cache_sheaves(kmalloc_caches[type][idx]);
+		}
+	}
+}
+
 void __init kmem_cache_init(void)
 {
 	static __initdata struct kmem_cache boot_kmem_cache,
@@ -8656,6 +8734,8 @@ void __init kmem_cache_init(void)
 	setup_kmalloc_cache_index_table();
 	create_kmalloc_caches();
 
+	bootstrap_kmalloc_sheaves();
+
 	/* Setup random freelists for each cache */
 	init_freelist_randomization();
 

-- 
2.52.0