Unexport do_add_mount() and add in follow_automount(), not ->d_automount()

[mv-sheeva.git] / fs / namei.c

diff --git a/fs/namei.c b/fs/namei.c
index 5c89695ae1e47754fc4e716854b3b8f6902f8f7c..c2e37727e3ab4d42df4aed32b3067b4f5f3856a8 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -900,6 +900,7 @@ static int follow_automount(struct path *path, unsigned flags,
                            bool *need_mntput)
 {
        struct vfsmount *mnt;
+       int err;
 
        if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
                return -EREMOTE;
@@ -942,22 +943,49 @@ static int follow_automount(struct path *path, unsigned flags,
                        return -EREMOTE;
                return PTR_ERR(mnt);
        }
+
        if (!mnt) /* mount collision */
                return 0;
 
+       /* The new mount record should have at least 2 refs to prevent it being
+        * expired before we get a chance to add it
+        */
+       BUG_ON(mnt_get_count(mnt) < 2);
+
        if (mnt->mnt_sb == path->mnt->mnt_sb &&
            mnt->mnt_root == path->dentry) {
+               mnt_clear_expiry(mnt);
+               mntput(mnt);
                mntput(mnt);
                return -ELOOP;
        }
 
-       dput(path->dentry);
-       if (*need_mntput)
-               mntput(path->mnt);
-       path->mnt = mnt;
-       path->dentry = dget(mnt->mnt_root);
-       *need_mntput = true;
-       return 0;
+       /* We need to add the mountpoint to the parent.  The filesystem may
+        * have placed it on an expiry list, and so we need to make sure it
+        * won't be expired under us if do_add_mount() fails (do_add_mount()
+        * will eat a reference unconditionally).
+        */
+       mntget(mnt);
+       err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
+       switch (err) {
+       case -EBUSY:
+               /* Someone else made a mount here whilst we were busy */
+               err = 0;
+       default:
+               mnt_clear_expiry(mnt);
+               mntput(mnt);
+               mntput(mnt);
+               return err;
+       case 0:
+               mntput(mnt);
+               dput(path->dentry);
+               if (*need_mntput)
+                       mntput(path->mnt);
+               path->mnt = mnt;
+               path->dentry = dget(mnt->mnt_root);
+               *need_mntput = true;
+               return 0;
+       }
 }
 
 /*