devpts: resolve devpts bind-mounts

[linux-2.6-block.git] / fs / devpts / inode.c

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 71b901936113d019f0bca169cca4a51154effab8..542364bf923e1884ead38cc717798857ff86b75f 100644 (file)
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -160,21 +160,27 @@ struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
        path = filp->f_path;
        path_get(&path);
 
-       /* Has the devpts filesystem already been found? */
-       if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC)
+       /* Walk upward while the start point is a bind mount of
+        * a single file.
+        */
+       while (path.mnt->mnt_root == path.dentry)
+               if (follow_up(&path) == 0)
+                       break;
+
+       /* devpts_ptmx_path() finds a devpts fs or returns an error. */
+       if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) ||
+           (DEVPTS_SB(path.mnt->mnt_sb) != fsi))
                err = devpts_ptmx_path(&path);
        dput(path.dentry);
-       if (err) {
-               mntput(path.mnt);
-               return ERR_PTR(err);
-       }
+       if (!err) {
+               if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
+                       return path.mnt;
 
-       if (DEVPTS_SB(path.mnt->mnt_sb) != fsi) {
-               mntput(path.mnt);
-               return ERR_PTR(-ENODEV);
+               err = -ENODEV;
        }
 
-       return path.mnt;
+       mntput(path.mnt);
+       return ERR_PTR(err);
 }
 
 struct pts_fs_info *devpts_acquire(struct file *filp)