NFS: Ensure the client submounts, when it crosses a server mountpoint.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
new file mode 100644
index 00000000000..a155505c36f
--- /dev/null
+++ b/fs/nfs/namespace.c
@@ -0,0 +1,89 @@
+/*
+ * linux/fs/nfs/namespace.c
+ *
+ * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
+ *
+ * NFS namespace
+ */
+
+#include <linux/config.h>
+
+#include <linux/dcache.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/nfs_fs.h>
+#include <linux/string.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/vfs.h>
+
+#define NFSDBG_FACILITY		NFSDBG_VFS
+
+/*
+ * nfs_follow_mountpoint - handle crossing a mountpoint on the server
+ * @dentry - dentry of mountpoint
+ * @nd - nameidata info
+ *
+ * When we encounter a mountpoint on the server, we want to set up
+ * a mountpoint on the client too, to prevent inode numbers from
+ * colliding, and to allow "df" to work properly.
+ * On NFSv4, we also want to allow for the fact that different
+ * filesystems may be migrated to different servers in a failover
+ * situation, and that different filesystems may want to use
+ * different security flavours.
+ */
+static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
+{
+	struct vfsmount *mnt;
+	struct nfs_server *server = NFS_SERVER(dentry->d_inode);
+	struct dentry *parent;
+	struct nfs_fh fh;
+	struct nfs_fattr fattr;
+	int err;
+
+	BUG_ON(IS_ROOT(dentry));
+	dprintk("%s: enter\n", __FUNCTION__);
+	dput(nd->dentry);
+	nd->dentry = dget(dentry);
+	if (d_mountpoint(nd->dentry))
+		goto out_follow;
+	/* Look it up again */
+	parent = dget_parent(nd->dentry);
+	err = server->rpc_ops->lookup(parent->d_inode, &nd->dentry->d_name, &fh, &fattr);
+	dput(parent);
+	if (err != 0)
+		goto out_err;
+
+	mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
+	err = PTR_ERR(mnt);
+	if (IS_ERR(mnt))
+		goto out_err;
+
+	mntget(mnt);
+	err = do_add_mount(mnt, nd, nd->mnt->mnt_flags, NULL);
+	if (err < 0) {
+		mntput(mnt);
+		if (err == -EBUSY)
+			goto out_follow;
+		goto out_err;
+	}
+	mntput(nd->mnt);
+	dput(nd->dentry);
+	nd->mnt = mnt;
+	nd->dentry = dget(mnt->mnt_root);
+out:
+	dprintk("%s: done, returned %d\n", __FUNCTION__, err);
+	return ERR_PTR(err);
+out_err:
+	path_release(nd);
+	goto out;
+out_follow:
+	while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
+		;
+	err = 0;
+	goto out;
+}
+
+struct inode_operations nfs_mountpoint_inode_operations = {
+	.follow_link	= nfs_follow_mountpoint,
+	.getattr	= nfs_getattr,
+};