getroot.c
3.47 KB
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/* getroot.c: get the root dentry for an NFS mount
*
* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/stats.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/lockd/bind.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include "internal.h"
#define NFSDBG_FACILITY NFSDBG_CLIENT
/*
* Set the superblock root dentry.
* Note that this function frees the inode in case of error.
*/
static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
{
/* The mntroot acts as the dummy root dentry for this superblock */
if (sb->s_root == NULL) {
sb->s_root = d_make_root(inode);
if (sb->s_root == NULL)
return -ENOMEM;
ihold(inode);
/*
* Ensure that this dentry is invisible to d_find_alias().
* Otherwise, it may be spliced into the tree by
* d_splice_alias 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(&d_inode(sb->s_root)->i_lock);
spin_lock(&sb->s_root->d_lock);
hlist_del_init(&sb->s_root->d_u.d_alias);
spin_unlock(&sb->s_root->d_lock);
spin_unlock(&d_inode(sb->s_root)->i_lock);
}
return 0;
}
/*
* get an NFS2/NFS3 root dentry from the root filehandle
*/
struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
const char *devname)
{
struct nfs_server *server = NFS_SB(sb);
struct nfs_fsinfo fsinfo;
struct dentry *ret;
struct inode *inode;
void *name = kstrdup(devname, GFP_KERNEL);
int error;
if (!name)
return ERR_PTR(-ENOMEM);
/* get the actual root for this mount */
fsinfo.fattr = nfs_alloc_fattr();
if (fsinfo.fattr == NULL) {
kfree(name);
return ERR_PTR(-ENOMEM);
}
error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
if (error < 0) {
dprintk("nfs_get_root: getattr error = %d\n", -error);
ret = ERR_PTR(error);
goto out;
}
inode = nfs_fhget(sb, mntfh, fsinfo.fattr, NULL);
if (IS_ERR(inode)) {
dprintk("nfs_get_root: get root inode failed\n");
ret = ERR_CAST(inode);
goto out;
}
error = nfs_superblock_set_dummy_root(sb, inode);
if (error != 0) {
ret = ERR_PTR(error);
goto out;
}
/* root dentries normally start off anonymous and get spliced in later
* if the dentry tree reaches them; however if the dentry already
* exists, we'll pick it up at this point and use it as the root
*/
ret = d_obtain_root(inode);
if (IS_ERR(ret)) {
dprintk("nfs_get_root: get root dentry failed\n");
goto out;
}
security_d_instantiate(ret, inode);
spin_lock(&ret->d_lock);
if (IS_ROOT(ret) && !ret->d_fsdata &&
!(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
ret->d_fsdata = name;
name = NULL;
}
spin_unlock(&ret->d_lock);
out:
kfree(name);
nfs_free_fattr(fsinfo.fattr);
return ret;
}