new helper: iterate_fd()

iterates through the opened files in given descriptor table,
calling a supplied function; we stop once non-zero is returned.
Callback gets struct file *, descriptor number and const void *
argument passed to iterator.  It is called with files->file_lock
held, so it is not allowed to block.

tty_io, netprio_cgroup and selinux flush_unauthorized_files()
converted to its use.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 12 insertions, 26 deletions

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index c75e3f9..5ffd084 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -272,38 +272,24 @@ out_free_devname:
 	return ret;
 }
 
+static int update_netprio(const void *v, struct file *file, unsigned n)
+{
+	int err;
+	struct socket *sock = sock_from_file(file, &err);
+	if (sock)
+		sock->sk->sk_cgrp_prioidx = (u32)(unsigned long)v;
+	return 0;
+}
+
 void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 {
 	struct task_struct *p;
+	void *v;
 
 	cgroup_taskset_for_each(p, cgrp, tset) {
-		unsigned int fd;
-		struct fdtable *fdt;
-		struct files_struct *files;
-
 		task_lock(p);
-		files = p->files;
-		if (!files) {
-			task_unlock(p);
-			continue;
-		}
-
-		spin_lock(&files->file_lock);
-		fdt = files_fdtable(files);
-		for (fd = 0; fd < fdt->max_fds; fd++) {
-			struct file *file;
-			struct socket *sock;
-			int err;
-
-			file = fcheck_files(files, fd);
-			if (!file)
-				continue;
-
-			sock = sock_from_file(file, &err);
-			if (sock)
-				sock_update_netprioidx(sock->sk, p);
-		}
-		spin_unlock(&files->file_lock);
+		v = (void *)(unsigned long)task_netprioidx(p);
+		iterate_fd(p->files, 0, update_netprio, v);
 		task_unlock(p);
 	}
 }