[RFC PATCH bpf-next 01/17] bpf: Link shimlink directly in trampoline

[Jiri Olsa <jolsa@xxxxxxxxxx>]

We are going to get rid of struct bpf_tramp_link in following
changes and cgroup_shim_find logic does not fit to that.

We can store the link directly in the trampoline and omit the
cgroup_shim_find searching logic.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 include/linux/bpf.h     |  3 +++
 kernel/bpf/trampoline.c | 23 +++--------------------
 2 files changed, 6 insertions(+), 20 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 20c26aed7896..ed2a921094bc 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -841,6 +841,8 @@ struct bpf_tramp_image {
 	};
 };
 
+struct bpf_shim_tramp_link;
+
 struct bpf_trampoline {
 	/* hlist for trampoline_table */
 	struct hlist_node hlist;
@@ -868,6 +870,7 @@ struct bpf_trampoline {
 	struct bpf_tramp_image *cur_image;
 	u64 selector;
 	struct module *mod;
+	struct bpf_shim_tramp_link *shim_link;
 };
 
 struct bpf_attach_target_info {
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index ff87e38af8a7..7a65d33cda60 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -689,24 +689,6 @@ static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog
 	return shim_link;
 }
 
-static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
-						    bpf_func_t bpf_func)
-{
-	struct bpf_tramp_link *link;
-	int kind;
-
-	for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
-		hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
-			struct bpf_prog *p = link->link.prog;
-
-			if (p->bpf_func == bpf_func)
-				return container_of(link, struct bpf_shim_tramp_link, link);
-		}
-	}
-
-	return NULL;
-}
-
 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
 				    int cgroup_atype)
 {
@@ -733,7 +715,7 @@ int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
 
 	mutex_lock(&tr->mutex);
 
-	shim_link = cgroup_shim_find(tr, bpf_func);
+	shim_link = tr->shim_link;
 	if (shim_link) {
 		/* Reusing existing shim attached by the other program. */
 		bpf_link_inc(&shim_link->link.link);
@@ -756,6 +738,7 @@ int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
 		goto err;
 
 	shim_link->trampoline = tr;
+	tr->shim_link = shim_link;
 	/* note, we're still holding tr refcnt from above */
 
 	mutex_unlock(&tr->mutex);
@@ -789,7 +772,7 @@ void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
 		return;
 
 	mutex_lock(&tr->mutex);
-	shim_link = cgroup_shim_find(tr, bpf_func);
+	shim_link = tr->shim_link;
 	mutex_unlock(&tr->mutex);
 
 	if (shim_link)
-- 
2.37.1