/* 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/nfs4_mount.h>
#include <linux/lockd/bind.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/nfs_idmap.h>
#include <linux/vfs.h>
#include <linux/namei.h>
#include <linux/security.h>

#include <asm/uaccess.h>

#include "nfs4_fs.h"
#include "delegation.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_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(&sb->s_root->d_inode->i_lock);
                spin_lock(&sb->s_root->d_lock);
                list_del_init(&sb->s_root->d_alias);
                spin_unlock(&sb->s_root->d_lock);
                spin_unlock(&sb->s_root->d_inode->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);
        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_alias(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_flags & DCACHE_NFSFS_RENAMED)) {
                ret->d_fsdata = name;
                name = NULL;
        }
        spin_unlock(&ret->d_lock);
out:
        if (name)
                kfree(name);
        nfs_free_fattr(fsinfo.fattr);
        return ret;
}

#ifdef CONFIG_NFS_V4

int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
{
        struct nfs_fsinfo fsinfo;
        int ret = -ENOMEM;

        dprintk("--> nfs4_get_rootfh()\n");

        fsinfo.fattr = nfs_alloc_fattr();
        if (fsinfo.fattr == NULL)
                goto out;

        /* Start by getting the root filehandle from the server */
        ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
        if (ret < 0) {
                dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
                goto out;
        }

        if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
                        || !S_ISDIR(fsinfo.fattr->mode)) {
                printk(KERN_ERR "nfs4_get_rootfh:"
                       " getroot encountered non-directory\n");
                ret = -ENOTDIR;
                goto out;
        }

        if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
                printk(KERN_ERR "nfs4_get_rootfh:"
                       " getroot obtained referral\n");
                ret = -EREMOTE;
                goto out;
        }

        memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
out:
        nfs_free_fattr(fsinfo.fattr);
        dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
        return ret;
}

/*
 * get an NFS4 root dentry from the root filehandle
 */
struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh,
                             const char *devname)
{
        struct nfs_server *server = NFS_SB(sb);
        struct nfs_fattr *fattr = NULL;
        struct dentry *ret;
        struct inode *inode;
        void *name = kstrdup(devname, GFP_KERNEL);
        int error;

        dprintk("--> nfs4_get_root()\n");

        if (!name)
                return ERR_PTR(-ENOMEM);

        /* get the info about the server and filesystem */
        error = nfs4_server_capabilities(server, mntfh);
        if (error < 0) {
                dprintk("nfs_get_root: getcaps error = %d\n",
                        -error);
                kfree(name);
                return ERR_PTR(error);
        }

        fattr = nfs_alloc_fattr();
        if (fattr == NULL) {
                kfree(name);
                return ERR_PTR(-ENOMEM);
        }

        /* get the actual root for this mount */
        error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
        if (error < 0) {
                dprintk("nfs_get_root: getattr error = %d\n", -error);
                ret = ERR_PTR(error);
                goto out;
        }

        if (fattr->valid & NFS_ATTR_FATTR_FSID &&
            !nfs_fsid_equal(&server->fsid, &fattr->fsid))
                memcpy(&server->fsid, &fattr->fsid, sizeof(server->fsid));

        inode = nfs_fhget(sb, mntfh, fattr);
        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_alias(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_flags & DCACHE_NFSFS_RENAMED)) {
                ret->d_fsdata = name;
                name = NULL;
        }
        spin_unlock(&ret->d_lock);
out:
        if (name)
                kfree(name);
        nfs_free_fattr(fattr);
        dprintk("<-- nfs4_get_root()\n");
        return ret;
}

#endif /* CONFIG_NFS_V4 */