bpf: trivial conversions for fdget()

fdget() is the first thing done in scope, all matching fdput() are
immediately followed by leaving the scope.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Author: Al Viro

kernel/bpf/btf.c

@@ -7676,21 +7676,16 @@ int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 struct btf *btf_get_by_fd(int fd)
 {
 	struct btf *btf;
-	struct fd f;
+	CLASS(fd, f)(fd);
 
-	f = fdget(fd);
-
-	if (!fd_file(f))
+	if (fd_empty(f))
 		return ERR_PTR(-EBADF);
 
-	if (fd_file(f)->f_op != &btf_fops) {
-		fdput(f);
+	if (fd_file(f)->f_op != &btf_fops)
 		return ERR_PTR(-EINVAL);
-	}
 
 	btf = fd_file(f)->private_data;
 	refcount_inc(&btf->refcnt);
-	fdput(f);
 
 	return btf;
 }

kernel/bpf/syscall.c

@@ -3187,20 +3187,16 @@ int bpf_link_new_fd(struct bpf_link *link)
 
 struct bpf_link *bpf_link_get_from_fd(u32 ufd)
 {
-	struct fd f = fdget(ufd);
+	CLASS(fd, f)(ufd);
 	struct bpf_link *link;
 
-	if (!fd_file(f))
+	if (fd_empty(f))
 		return ERR_PTR(-EBADF);
-	if (fd_file(f)->f_op != &bpf_link_fops && fd_file(f)->f_op != &bpf_link_fops_poll) {
-		fdput(f);
+	if (fd_file(f)->f_op != &bpf_link_fops && fd_file(f)->f_op != &bpf_link_fops_poll)
 		return ERR_PTR(-EINVAL);
-	}
 
 	link = fd_file(f)->private_data;
 	bpf_link_inc(link);
-	fdput(f);
-
 	return link;
 }
 EXPORT_SYMBOL(bpf_link_get_from_fd);

kernel/bpf/token.c

@@ -232,19 +232,16 @@ int bpf_token_create(union bpf_attr *attr)
 
 struct bpf_token *bpf_token_get_from_fd(u32 ufd)
 {
-	struct fd f = fdget(ufd);
+	CLASS(fd, f)(ufd);
 	struct bpf_token *token;
 
-	if (!fd_file(f))
+	if (fd_empty(f))
 		return ERR_PTR(-EBADF);
-	if (fd_file(f)->f_op != &bpf_token_fops) {
-		fdput(f);
+	if (fd_file(f)->f_op != &bpf_token_fops)
 		return ERR_PTR(-EINVAL);
-	}
 
 	token = fd_file(f)->private_data;
 	bpf_token_inc(token);
-	fdput(f);
 
 	return token;
 }