[PATCH RFC 4/8] mm/slab: allow bootstrap_cache_sheaves() to fail

[Harry Yoo (Oracle)]

Panicking on sheaf allocation failure is acceptable during boot, but
to allow changing the sheaf capacity at runtime, the bootstrap path
must be able to propagate errors instead. Return an error code from
bootstrap_cache_sheaves() so callers can decide how to react.

Change it to return an int (0 on success, negative errno on failure),
accept capacity as a parameter, and drop __init. Callers without a
user-specified capacity pass zero to use the default capacity
calculated by the slab allocator. Failures are now handled by the
caller.

Signed-off-by: Harry Yoo (Oracle) <harry@xxxxxxxxxx>
---
 mm/slub.c | 46 ++++++++++++++++++++++++++--------------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 44f36ae32570..fb98d0da5c78 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -8462,18 +8462,18 @@ static struct kmem_cache * __init bootstrap(struct kmem_cache *static_cache)
  * 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)
+static int bootstrap_cache_sheaves(struct kmem_cache *s,
+				   unsigned short capacity)
 {
 	struct kmem_cache_args empty_args = {};
-	unsigned short capacity;
-	bool failed = false;
-	int node, cpu;
+	int node, cpu, err = 0;
 
-	capacity = calculate_sheaf_capacity(s, &empty_args);
+	if (!capacity)
+		capacity = calculate_sheaf_capacity(s, &empty_args);
 
 	/* capacity can be 0 due to debugging or SLUB_TINY */
 	if (!capacity)
-		return;
+		return 0;
 
 	for_each_node_mask(node, slab_barn_nodes) {
 		struct node_barn *barn;
@@ -8481,7 +8481,7 @@ static void __init bootstrap_cache_sheaves(struct kmem_cache *s)
 		barn = kmalloc_node(sizeof(*barn), GFP_KERNEL, node);
 
 		if (!barn) {
-			failed = true;
+			err = -ENOMEM;
 			goto out;
 		}
 
@@ -8497,31 +8497,37 @@ static void __init bootstrap_cache_sheaves(struct kmem_cache *s)
 		pcs->main = __alloc_empty_sheaf(s, GFP_KERNEL, capacity);
 
 		if (!pcs->main) {
-			failed = true;
+			err = -ENOMEM;
 			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);
+	if (!err)
+		s->sheaf_capacity = capacity;
 
-	s->sheaf_capacity = capacity;
+	return err;
 }
 
+#define for_each_normal_kmalloc_cache(s, type, idx) \
+	for (type = KMALLOC_NORMAL; type <= KMALLOC_RANDOM_END; type++)	\
+		for (idx = 0; idx < KMALLOC_SHIFT_HIGH + 1; idx++)	\
+			if ((s = kmalloc_caches[type][idx]))
+
 static void __init bootstrap_kmalloc_sheaves(void)
 {
 	enum kmalloc_cache_type type;
+	struct kmem_cache *s;
+	int idx;
 
-	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]);
-		}
+	for_each_normal_kmalloc_cache(s, type, idx) {
+		/*
+		 * It's still early in boot so treat this as a failure to
+		 * create the kmalloc cache in the first place.
+		 */
+		if (bootstrap_cache_sheaves(s, 0))
+			panic("Out of memory when creating kmem_cache %s\n",
+			      s->name);
 	}
 }
 

-- 
2.43.0