NFS: Fix an Oops in NFS unmount
Ensure that the dummy 'root dentry' is invisible to d_find_alias(). If not,
then it may be spliced into the tree if a parent directory from the same
filesystem gets mounted at a later time.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index 0ee4384..e6242cd 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -57,6 +57,17 @@
}
/* Circumvent igrab(): we know the inode is not being freed */
atomic_inc(&inode->i_count);
+ /*
+ * Ensure that this dentry is invisible to d_find_alias().
+ * Otherwise, it may be spliced into the tree by
+ * d_materialise_unique if a parent directory from the same
+ * filesystem gets mounted at a later time.
+ * This again causes shrink_dcache_for_umount_subtree() to
+ * Oops, since the test for IS_ROOT() will fail.
+ */
+ spin_lock(&dcache_lock);
+ list_del_init(&sb->s_root->d_alias);
+ spin_unlock(&dcache_lock);
}
return 0;
}