/* 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/system.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_alloc_root(inode);
                if (sb->s_root == NULL) {
                        iput(inode);
                        return -ENOMEM;
                }
                /* 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;
}

/*
 * get an NFS2/NFS3 root dentry from the root filehandle
 */
struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
{
        struct nfs_server *server = NFS_SB(sb);
        struct nfs_fsinfo fsinfo;
        struct nfs_fattr fattr;
        struct dentry *mntroot;
        struct inode *inode;
        int error;

        /* get the actual root for this mount */
        fsinfo.fattr = &fattr;

        error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
        if (error < 0) {
                dprintk("nfs_get_root: getattr error = %d\n", -error);
                return ERR_PTR(error);
        }

        inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
        if (IS_ERR(inode)) {
                dprintk("nfs_get_root: get root inode failed\n");
                return ERR_CAST(inode);
        }

        error = nfs_superblock_set_dummy_root(sb, inode);
        if (error != 0)
                return ERR_PTR(error);

        /* 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
         */
        mntroot = d_obtain_alias(inode);
        if (IS_ERR(mntroot)) {
                dprintk("nfs_get_root: get root dentry failed\n");
                return mntroot;
        }

        security_d_instantiate(mntroot, inode);

        if (!mntroot->d_op)
                mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;

        return mntroot;
}

#ifdef CONFIG_NFS_V4

/*
 * Do a simple pathwalk from the root FH of the server to the nominated target
 * of the mountpoint
 * - give error on symlinks
 * - give error on ".." occurring in the path
 * - follow traversals
 */
int nfs4_path_walk(struct nfs_server *server,
                   struct nfs_fh *mntfh,
                   const char *path)
{
        struct nfs_fsinfo fsinfo;
        struct nfs_fattr fattr;
        struct nfs_fh lastfh;
        struct qstr name;
        int ret;

        dprintk("--> nfs4_path_walk(,,%s)\n", path);

        fsinfo.fattr = &fattr;
        nfs_fattr_init(&fattr);

        /* Eat leading slashes */
        while (*path == '/')
                path++;

        /* 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_root: getroot error = %d\n", -ret);
                return ret;
        }

        if (!S_ISDIR(fattr.mode)) {
                printk(KERN_ERR "nfs4_get_root:"
                       " getroot encountered non-directory\n");
                return -ENOTDIR;
        }

        /* FIXME: It is quite valid for the server to return a referral here */
        if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
                printk(KERN_ERR "nfs4_get_root:"
                       " getroot obtained referral\n");
                return -EREMOTE;
        }

next_component:
        dprintk("Next: %s\n", path);

        /* extract the next bit of the path */
        if (!*path)
                goto path_walk_complete;

        name.name = path;
        while (*path && *path != '/')
                path++;
        name.len = path - (const char *) name.name;

        if (name.len > NFS4_MAXNAMLEN)
                return -ENAMETOOLONG;

eat_dot_dir:
        while (*path == '/')
                path++;

        if (path[0] == '.' && (path[1] == '/' || !path[1])) {
                path += 2;
                goto eat_dot_dir;
        }

        /* FIXME: Why shouldn't the user be able to use ".." in the path? */
        if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
            ) {
                printk(KERN_ERR "nfs4_get_root:"
                       " Mount path contains reference to \"..\"\n");
                return -EINVAL;
        }

        /* lookup the next FH in the sequence */
        memcpy(&lastfh, mntfh, sizeof(lastfh));

        dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);

        ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
                                                    mntfh, &fattr);
        if (ret < 0) {
                dprintk("nfs4_get_root: getroot error = %d\n", -ret);
                return ret;
        }

        if (!S_ISDIR(fattr.mode)) {
                printk(KERN_ERR "nfs4_get_root:"
                       " lookupfh encountered non-directory\n");
                return -ENOTDIR;
        }

        /* FIXME: Referrals are quite valid here too */
        if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
                printk(KERN_ERR "nfs4_get_root:"
                       " lookupfh obtained referral\n");
                return -EREMOTE;
        }

        goto next_component;

path_walk_complete:
        memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
        dprintk("<-- nfs4_path_walk() = 0\n");
        return 0;
}

/*
 * get an NFS4 root dentry from the root filehandle
 */
struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
{
        struct nfs_server *server = NFS_SB(sb);
        struct nfs_fattr fattr;
        struct dentry *mntroot;
        struct inode *inode;
        int error;

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

        /* 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);
                return ERR_PTR(error);
        }

        /* 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);
                return ERR_PTR(error);
        }

        inode = nfs_fhget(sb, mntfh, &fattr);
        if (IS_ERR(inode)) {
                dprintk("nfs_get_root: get root inode failed\n");
                return ERR_CAST(inode);
        }

        error = nfs_superblock_set_dummy_root(sb, inode);
        if (error != 0)
                return ERR_PTR(error);

        /* 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
         */
        mntroot = d_obtain_alias(inode);
        if (IS_ERR(mntroot)) {
                dprintk("nfs_get_root: get root dentry failed\n");
                return mntroot;
        }

        security_d_instantiate(mntroot, inode);

        if (!mntroot->d_op)
                mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;

        dprintk("<-- nfs4_get_root()\n");
        return mntroot;
}

#endif /* CONFIG_NFS_V4 */