bpf, maps: add release callback

Add a release callback for maps that is invoked when the last
reference to its struct file is gone and the struct file about
to be released by vfs. The handler will be used by fd array maps.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 2 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1bcae82c6cb1..29b5a1ae22cb 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -19,7 +19,8 @@ struct bpf_map;
 struct bpf_map_ops {
         /* funcs callable from userspace (via syscall) */
         struct bpf_map *(*map_alloc)(union bpf_attr *attr);
-        void (*map_free)(struct bpf_map *);
+        void (*map_release)(struct bpf_map *map, struct file *map_file);
+        void (*map_free)(struct bpf_map *map);
         int (*map_get_next_key)(struct bpf_map *map, void *key, void *next_key);
 
         /* funcs callable from userspace and from eBPF programs */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 46ecce4b79ed..fc3adcd064b1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -124,7 +124,12 @@ void bpf_map_put_with_uref(struct bpf_map *map)
 
 static int bpf_map_release(struct inode *inode, struct file *filp)
 {
-        bpf_map_put_with_uref(filp->private_data);
+        struct bpf_map *map = filp->private_data;
+
+        if (map->ops->map_release)
+                map->ops->map_release(map, filp);
+
+        bpf_map_put_with_uref(map);
         return 0;
 }