pidns: call pid_ns_prepare_proc() from create_pid_namespace()

Reorganize proc_get_sb() so it can be called before the struct pid of the
first process is allocated.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 18 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index ef9fa8e24ad6..e5e2bfa7a03b 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -43,17 +43,6 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
         struct pid_namespace *ns;
         struct proc_inode *ei;
 
-        if (proc_mnt) {
-                /* Seed the root directory with a pid so it doesn't need
-                 * to be special in base.c.  I would do this earlier but
-                 * the only task alive when /proc is mounted the first time
-                 * is the init_task and it doesn't have any pids.
-                 */
-                ei = PROC_I(proc_mnt->mnt_sb->s_root->d_inode);
-                if (!ei->pid)
-                        ei->pid = find_get_pid(1);
-        }
-
         if (flags & MS_KERNMOUNT)
                 ns = (struct pid_namespace *)data;
         else
@@ -71,16 +60,16 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
                         return ERR_PTR(err);
                 }
 
-                ei = PROC_I(sb->s_root->d_inode);
-                if (!ei->pid) {
-                        rcu_read_lock();
-                        ei->pid = get_pid(find_pid_ns(1, ns));
-                        rcu_read_unlock();
-                }
-
                 sb->s_flags |= MS_ACTIVE;
         }
 
+        ei = PROC_I(sb->s_root->d_inode);
+        if (!ei->pid) {
+                rcu_read_lock();
+                ei->pid = get_pid(find_pid_ns(1, ns));
+                rcu_read_unlock();
+        }
+
         return dget(sb->s_root);
 }