Patch "bpf: Only allocate one bpf_mem_cache for bpf_cpumask_ma" has been added to the 6.3-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bpf: Only allocate one bpf_mem_cache for bpf_cpumask_ma

to the 6.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-only-allocate-one-bpf_mem_cache-for-bpf_cpumask_.patch
and it can be found in the queue-6.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a9d8b13a97a82efe9947d2a9df82f8f91b8530a6
Author: Hou Tao <houtao1@xxxxxxxxxx>
Date:   Thu Feb 16 10:48:21 2023 +0800

    bpf: Only allocate one bpf_mem_cache for bpf_cpumask_ma
    
    [ Upstream commit 5d5de3a431d87ac51d43da8d796891d014975ab7 ]
    
    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@xxxxxxxxxx>
    Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230216024821.2202916-1-houtao@xxxxxxxxxxxxxxx
    Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
    Stable-dep-of: 77473d1a962f ("bpf: Free struct bpf_cpumask in call_rcu handler")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/bpf_mem_alloc.h b/include/linux/bpf_mem_alloc.h
index 3e164b8efaa92..a7104af61ab4d 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);
 
diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 52b981512a351..2b3fbbfebdc5f 100644
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -55,7 +55,7 @@ __bpf_kfunc struct bpf_cpumask *bpf_cpumask_create(void)
 	/* cpumask must be the first element so struct bpf_cpumask be cast to struct cpumask. */
 	BUILD_BUG_ON(offsetof(struct bpf_cpumask, cpumask) != 0);
 
-	cpumask = bpf_mem_alloc(&bpf_cpumask_ma, sizeof(*cpumask));
+	cpumask = bpf_mem_cache_alloc(&bpf_cpumask_ma);
 	if (!cpumask)
 		return NULL;
 
@@ -123,7 +123,7 @@ __bpf_kfunc void bpf_cpumask_release(struct bpf_cpumask *cpumask)
 
 	if (refcount_dec_and_test(&cpumask->usage)) {
 		migrate_disable();
-		bpf_mem_free(&bpf_cpumask_ma, cpumask);
+		bpf_mem_cache_free(&bpf_cpumask_ma, cpumask);
 		migrate_enable();
 	}
 }
@@ -468,7 +468,7 @@ static int __init cpumask_kfunc_init(void)
 		},
 	};
 
-	ret = bpf_mem_alloc_init(&bpf_cpumask_ma, 0, false);
+	ret = bpf_mem_alloc_init(&bpf_cpumask_ma, sizeof(struct bpf_cpumask), false);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &cpumask_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &cpumask_kfunc_set);
 	return  ret ?: register_btf_id_dtor_kfuncs(cpumask_dtors,