/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * symlink.c - operations for configfs symlinks.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 *
 * Based on sysfs:
 *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
 *
 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/namei.h>

#include <linux/configfs.h>
#include "configfs_internal.h"

/* Protects attachments of new symlinks */
DEFINE_MUTEX(configfs_symlink_mutex);

static int item_depth(struct config_item * item)
{
        struct config_item * p = item;
        int depth = 0;
        do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
        return depth;
}

static int item_path_length(struct config_item * item)
{
        struct config_item * p = item;
        int length = 1;
        do {
                length += strlen(config_item_name(p)) + 1;
                p = p->ci_parent;
        } while (p && !configfs_is_root(p));
        return length;
}

static void fill_item_path(struct config_item * item, char * buffer, int length)
{
        struct config_item * p;

        --length;
        for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
                int cur = strlen(config_item_name(p));

                /* back up enough to print this bus id with '/' */
                length -= cur;
                strncpy(buffer + length,config_item_name(p),cur);
                *(buffer + --length) = '/';
        }
}

static int create_link(struct config_item *parent_item,
                       struct config_item *item,
                       struct dentry *dentry)
{
        struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
        struct configfs_symlink *sl;
        int ret;

        ret = -ENOENT;
        if (!configfs_dirent_is_ready(target_sd))
                goto out;
        ret = -ENOMEM;
        sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
        if (sl) {
                sl->sl_target = config_item_get(item);
                spin_lock(&configfs_dirent_lock);
                if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
                        spin_unlock(&configfs_dirent_lock);
                        config_item_put(item);
                        kfree(sl);
                        return -ENOENT;
                }
                list_add(&sl->sl_list, &target_sd->s_links);
                spin_unlock(&configfs_dirent_lock);
                ret = configfs_create_link(sl, parent_item->ci_dentry,
                                           dentry);
                if (ret) {
                        spin_lock(&configfs_dirent_lock);
                        list_del_init(&sl->sl_list);
                        spin_unlock(&configfs_dirent_lock);
                        config_item_put(item);
                        kfree(sl);
                }
        }

out:
        return ret;
}


static int get_target(const char *symname, struct path *path,
                      struct config_item **target)
{
        int ret;

        ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
        if (!ret) {
                if (path->dentry->d_sb == configfs_sb) {
                        *target = configfs_get_config_item(path->dentry);
                        if (!*target) {
                                ret = -ENOENT;
                                path_put(path);
                        }
                } else
                        ret = -EPERM;
        }

        return ret;
}


int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
        int ret;
        struct path path;
        struct configfs_dirent *sd;
        struct config_item *parent_item;
        struct config_item *target_item = NULL;
        struct config_item_type *type;

        ret = -EPERM;  /* What lack-of-symlink returns */
        if (dentry->d_parent == configfs_sb->s_root)
                goto out;

        sd = dentry->d_parent->d_fsdata;
        /*
         * Fake invisibility if dir belongs to a group/default groups hierarchy
         * being attached
         */
        ret = -ENOENT;
        if (!configfs_dirent_is_ready(sd))
                goto out;

        parent_item = configfs_get_config_item(dentry->d_parent);
        type = parent_item->ci_type;

        ret = -EPERM;
        if (!type || !type->ct_item_ops ||
            !type->ct_item_ops->allow_link)
                goto out_put;

        ret = get_target(symname, &path, &target_item);
        if (ret)
                goto out_put;

        ret = type->ct_item_ops->allow_link(parent_item, target_item);
        if (!ret) {
                mutex_lock(&configfs_symlink_mutex);
                ret = create_link(parent_item, target_item, dentry);
                mutex_unlock(&configfs_symlink_mutex);
                if (ret && type->ct_item_ops->drop_link)
                        type->ct_item_ops->drop_link(parent_item,
                                                     target_item);
        }

        config_item_put(target_item);
        path_put(&path);

out_put:
        config_item_put(parent_item);

out:
        return ret;
}

int configfs_unlink(struct inode *dir, struct dentry *dentry)
{
        struct configfs_dirent *sd = dentry->d_fsdata;
        struct configfs_symlink *sl;
        struct config_item *parent_item;
        struct config_item_type *type;
        int ret;

        ret = -EPERM;  /* What lack-of-symlink returns */
        if (!(sd->s_type & CONFIGFS_ITEM_LINK))
                goto out;

        BUG_ON(dentry->d_parent == configfs_sb->s_root);

        sl = sd->s_element;

        parent_item = configfs_get_config_item(dentry->d_parent);
        type = parent_item->ci_type;

        spin_lock(&configfs_dirent_lock);
        list_del_init(&sd->s_sibling);
        spin_unlock(&configfs_dirent_lock);
        configfs_drop_dentry(sd, dentry->d_parent);
        dput(dentry);
        configfs_put(sd);

        /*
         * drop_link() must be called before
         * list_del_init(&sl->sl_list), so that the order of
         * drop_link(this, target) and drop_item(target) is preserved.
         */
        if (type && type->ct_item_ops &&
            type->ct_item_ops->drop_link)
                type->ct_item_ops->drop_link(parent_item,
                                               sl->sl_target);

        spin_lock(&configfs_dirent_lock);
        list_del_init(&sl->sl_list);
        spin_unlock(&configfs_dirent_lock);

        /* Put reference from create_link() */
        config_item_put(sl->sl_target);
        kfree(sl);

        config_item_put(parent_item);

        ret = 0;

out:
        return ret;
}

static int configfs_get_target_path(struct config_item * item, struct config_item * target,
                                   char *path)
{
        char * s;
        int depth, size;

        depth = item_depth(item);
        size = item_path_length(target) + depth * 3 - 1;
        if (size > PATH_MAX)
                return -ENAMETOOLONG;

        pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);

        for (s = path; depth--; s += 3)
                strcpy(s,"../");

        fill_item_path(target, path, size);
        pr_debug("%s: path = '%s'\n", __func__, path);

        return 0;
}

static int configfs_getlink(struct dentry *dentry, char * path)
{
        struct config_item *item, *target_item;
        int error = 0;

        item = configfs_get_config_item(dentry->d_parent);
        if (!item)
                return -EINVAL;

        target_item = configfs_get_config_item(dentry);
        if (!target_item) {
                config_item_put(item);
                return -EINVAL;
        }

        down_read(&configfs_rename_sem);
        error = configfs_get_target_path(item, target_item, path);
        up_read(&configfs_rename_sem);

        config_item_put(item);
        config_item_put(target_item);
        return error;

}

static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
        int error = -ENOMEM;
        unsigned long page = get_zeroed_page(GFP_KERNEL);

        if (page) {
                error = configfs_getlink(dentry, (char *)page);
                if (!error) {
                        nd_set_link(nd, (char *)page);
                        return (void *)page;
                }
        }

        nd_set_link(nd, ERR_PTR(error));
        return NULL;
}

static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
                              void *cookie)
{
        if (cookie) {
                unsigned long page = (unsigned long)cookie;
                free_page(page);
        }
}

const struct inode_operations configfs_symlink_inode_operations = {
        .follow_link = configfs_follow_link,
        .readlink = generic_readlink,
        .put_link = configfs_put_link,
        .setattr = configfs_setattr,
};