From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Wed, 12 Dec 2007 16:12:15 +0000 (-0500)
Subject: NFS: Fix an Oops in NFS unmount
X-Git-Tag: v2.6.24-rc6~56^2~1
X-Git-Url: http://pileus.org/git/?a=commitdiff_plain;h=a10db50a4ae813fcb2f431f2fb039933c109a925;p=~andy%2Flinux

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 0ee43843f4e..e6242cdbaf9 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -57,6 +57,17 @@ static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *i
 		}
 		/* 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;
 }