bpf: Only allocate one bpf_mem_cache for bpf_cpumask_ma

The size of bpf_cpumask is fixed, so there is no need to allocate many
bpf_mem_caches for bpf_cpumask_ma, just one bpf_mem_cache is enough.
Also add comments for bpf_mem_alloc_init() in bpf_mem_alloc.h to prevent
future miuse.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230216024821.2202916-1-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/bpf_mem_alloc.h b/include/linux/bpf_mem_alloc.h
index 3e164b8efaa9..a7104af61ab4 100644
--- a/include/linux/bpf_mem_alloc.h
+++ b/include/linux/bpf_mem_alloc.h
@@ -14,6 +14,13 @@ struct bpf_mem_alloc {
 	struct work_struct work;
 };
 
+/* 'size != 0' is for bpf_mem_alloc which manages fixed-size objects.
+ * Alloc and free are done with bpf_mem_cache_{alloc,free}().
+ *
+ * 'size = 0' is for bpf_mem_alloc which manages many fixed-size objects.
+ * Alloc and free are done with bpf_mem_{alloc,free}() and the size of
+ * the returned object is given by the size argument of bpf_mem_alloc().
+ */
 int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu);
 void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma);