Subject: [PATCH v2 bpf-next 02/10] bpf: rework cgroup storage pointer passing

From: Roman Gushchin <[email-masked]>
Date: Tue, 25 Sep 2018 16:21:06 +0100

To simplify the following introduction of per-cpu cgroup storage,
let's rework a bit a mechanism of passing a pointer to a cgroup
storage into the bpf_get_local_storage(). Let's save a pointer
to the corresponding bpf_cgroup_storage structure, instead of
a pointer to the actual buffer.

It will help us to handle per-cpu storage later, which has
a different way of accessing to the actual data.

Signed-off-by: Roman Gushchin <[email-masked]>
Acked-by: Song Liu <[email-masked]>
Cc: Daniel Borkmann <[email-masked]>
Cc: Alexei Starovoitov <[email-masked]>
---
 include/linux/bpf-cgroup.h | 13 ++++---------
 kernel/bpf/helpers.c       |  8 ++++++--
 kernel/bpf/local_storage.c |  3 ++-
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index e9871b012dac..7e0c9a1d48b7 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -23,7 +23,8 @@ struct bpf_cgroup_storage;
 extern struct static_key_false cgroup_bpf_enabled_key;
 #define cgroup_bpf_enabled static_branch_unlikely(&cgroup_bpf_enabled_key)
 
-DECLARE_PER_CPU(void*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
+DECLARE_PER_CPU(struct bpf_cgroup_storage*,
+		bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
 
 #define for_each_cgroup_storage_type(stype) \
 	for (stype = 0; stype < MAX_BPF_CGROUP_STORAGE_TYPE; stype++)
@@ -115,15 +116,9 @@ static inline void bpf_cgroup_storage_set(struct bpf_cgroup_storage
 					  *storage[MAX_BPF_CGROUP_STORAGE_TYPE])
 {
 	enum bpf_cgroup_storage_type stype;
-	struct bpf_storage_buffer *buf;
-
-	for_each_cgroup_storage_type(stype) {
-		if (!storage[stype])
-			continue;
 
-		buf = READ_ONCE(storage[stype]->buf);
-		this_cpu_write(bpf_cgroup_storage[stype], &buf->data[0]);
-	}
+	for_each_cgroup_storage_type(stype)
+		this_cpu_write(bpf_cgroup_storage[stype], storage[stype]);
 }
 
 struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 9070b2ace6aa..e42f8789b7ea 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -195,7 +195,8 @@ const struct bpf_func_proto bpf_get_current_cgroup_id_proto = {
 };
 
 #ifdef CONFIG_CGROUP_BPF
-DECLARE_PER_CPU(void*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
+DECLARE_PER_CPU(struct bpf_cgroup_storage*,
+		bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
 
 BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags)
 {
@@ -204,8 +205,11 @@ BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags)
 	 * verifier checks that its value is correct.
 	 */
 	enum bpf_cgroup_storage_type stype = cgroup_storage_type(map);
+	struct bpf_cgroup_storage *storage;
 
-	return (unsigned long) this_cpu_read(bpf_cgroup_storage[stype]);
+	storage = this_cpu_read(bpf_cgroup_storage[stype]);
+
+	return (unsigned long)&READ_ONCE(storage->buf)->data[0];
 }
 
 const struct bpf_func_proto bpf_get_local_storage_proto = {
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 0bd9f19fc557..6742292fb39e 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -7,7 +7,8 @@
 #include <linux/rbtree.h>
 #include <linux/slab.h>
 
-DEFINE_PER_CPU(void*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
+DEFINE_PER_CPU(struct bpf_cgroup_storage*,
+	       bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
 
 #ifdef CONFIG_CGROUP_BPF
 
-- 
2.17.1