bpf: Add support for non-fix-size percpu mem allocation

This is needed for later percpu mem allocation when the
allocation is done by bpf program. For such cases, a global
bpf_global_percpu_ma is added where a flexible allocation
size is needed.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230827152734.1995725-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -55,8 +55,8 @@ struct cgroup;
 extern struct idr btf_idr;
 extern spinlock_t btf_idr_lock;
 extern struct kobject *btf_kobj;
-extern struct bpf_mem_alloc bpf_global_ma;
-extern bool bpf_global_ma_set;
+extern struct bpf_mem_alloc bpf_global_ma, bpf_global_percpu_ma;
+extern bool bpf_global_ma_set, bpf_global_percpu_ma_set;
 
 typedef u64 (*bpf_callback_t)(u64, u64, u64, u64, u64);
 typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,

kernel/bpf/core.c

@@ -64,8 +64,8 @@
 #define OFF	insn->off
 #define IMM	insn->imm
 
-struct bpf_mem_alloc bpf_global_ma;
-bool bpf_global_ma_set;
+struct bpf_mem_alloc bpf_global_ma, bpf_global_percpu_ma;
+bool bpf_global_ma_set, bpf_global_percpu_ma_set;
 
 /* No hurry in this branch
  *
@@ -2921,7 +2921,9 @@ static int __init bpf_global_ma_init(void)
 
 	ret = bpf_mem_alloc_init(&bpf_global_ma, 0, false);
 	bpf_global_ma_set = !ret;
-	return ret;
+	ret = bpf_mem_alloc_init(&bpf_global_percpu_ma, 0, true);
+	bpf_global_percpu_ma_set = !ret;
+	return !bpf_global_ma_set || !bpf_global_percpu_ma_set;
 }
 late_initcall(bpf_global_ma_init);
 #endif

kernel/bpf/memalloc.c

@@ -499,15 +499,16 @@ int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu)
 	struct obj_cgroup *objcg = NULL;
 	int cpu, i, unit_size, percpu_size = 0;
 
+	/* room for llist_node and per-cpu pointer */
+	if (percpu)
+		percpu_size = LLIST_NODE_SZ + sizeof(void *);
+
 	if (size) {
 		pc = __alloc_percpu_gfp(sizeof(*pc), 8, GFP_KERNEL);
 		if (!pc)
 			return -ENOMEM;
 
-		if (percpu)
-			/* room for llist_node and per-cpu pointer */
-			percpu_size = LLIST_NODE_SZ + sizeof(void *);
-		else
+		if (!percpu)
 			size += LLIST_NODE_SZ; /* room for llist_node */
 		unit_size = size;
 
@@ -527,10 +528,6 @@ int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu)
 		return 0;
 	}
 
-	/* size == 0 && percpu is an invalid combination */
-	if (WARN_ON_ONCE(percpu))
-		return -EINVAL;
-
 	pcc = __alloc_percpu_gfp(sizeof(*cc), 8, GFP_KERNEL);
 	if (!pcc)
 		return -ENOMEM;
@@ -543,6 +540,7 @@ int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu)
 			c = &cc->cache[i];
 			c->unit_size = sizes[i];
 			c->objcg = objcg;
+			c->percpu_size = percpu_size;
 			c->tgt = c;
 			prefill_mem_cache(c, cpu);
 		}