/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * inode.c - basic inode and dentry operations.
 *
 * 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.
 *
 * Please see Documentation/filesystems/configfs.txt for more information.
 */

#undef DEBUG

#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/sched.h>

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

extern struct super_block * configfs_sb;

static const struct address_space_operations configfs_aops = {
        .readpage       = simple_readpage,
        .write_begin    = simple_write_begin,
        .write_end      = simple_write_end,
};

static struct backing_dev_info configfs_backing_dev_info = {
        .ra_pages       = 0,    /* No readahead */
        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};

static const struct inode_operations configfs_inode_operations ={
        .setattr        = configfs_setattr,
};

int configfs_setattr(struct dentry * dentry, struct iattr * iattr)
{
        struct inode * inode = dentry->d_inode;
        struct configfs_dirent * sd = dentry->d_fsdata;
        struct iattr * sd_iattr;
        unsigned int ia_valid = iattr->ia_valid;
        int error;

        if (!sd)
                return -EINVAL;

        sd_iattr = sd->s_iattr;

        error = inode_change_ok(inode, iattr);
        if (error)
                return error;

        error = inode_setattr(inode, iattr);
        if (error)
                return error;

        if (!sd_iattr) {
                /* setting attributes for the first time, allocate now */
                sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
                if (!sd_iattr)
                        return -ENOMEM;
                /* assign default attributes */
                sd_iattr->ia_mode = sd->s_mode;
                sd_iattr->ia_uid = 0;
                sd_iattr->ia_gid = 0;
                sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
                sd->s_iattr = sd_iattr;
        }

        /* attributes were changed atleast once in past */

        if (ia_valid & ATTR_UID)
                sd_iattr->ia_uid = iattr->ia_uid;
        if (ia_valid & ATTR_GID)
                sd_iattr->ia_gid = iattr->ia_gid;
        if (ia_valid & ATTR_ATIME)
                sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
                                                inode->i_sb->s_time_gran);
        if (ia_valid & ATTR_MTIME)
                sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
                                                inode->i_sb->s_time_gran);
        if (ia_valid & ATTR_CTIME)
                sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
                                                inode->i_sb->s_time_gran);
        if (ia_valid & ATTR_MODE) {
                umode_t mode = iattr->ia_mode;

                if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
                        mode &= ~S_ISGID;
                sd_iattr->ia_mode = sd->s_mode = mode;
        }

        return error;
}

static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
{
        inode->i_mode = mode;
        inode->i_uid = 0;
        inode->i_gid = 0;
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
}

static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
{
        inode->i_mode = iattr->ia_mode;
        inode->i_uid = iattr->ia_uid;
        inode->i_gid = iattr->ia_gid;
        inode->i_atime = iattr->ia_atime;
        inode->i_mtime = iattr->ia_mtime;
        inode->i_ctime = iattr->ia_ctime;
}

struct inode * configfs_new_inode(mode_t mode, struct configfs_dirent * sd)
{
        struct inode * inode = new_inode(configfs_sb);
        if (inode) {
                inode->i_blocks = 0;
                inode->i_mapping->a_ops = &configfs_aops;
                inode->i_mapping->backing_dev_info = &configfs_backing_dev_info;
                inode->i_op = &configfs_inode_operations;

                if (sd->s_iattr) {
                        /* sysfs_dirent has non-default attributes
                         * get them for the new inode from persistent copy
                         * in sysfs_dirent
                         */
                        set_inode_attr(inode, sd->s_iattr);
                } else
                        set_default_inode_attr(inode, mode);
        }
        return inode;
}

int configfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
{
        int error = 0;
        struct inode * inode = NULL;
        if (dentry) {
                if (!dentry->d_inode) {
                        struct configfs_dirent *sd = dentry->d_fsdata;
                        if ((inode = configfs_new_inode(mode, sd))) {
                                if (dentry->d_parent && dentry->d_parent->d_inode) {
                                        struct inode *p_inode = dentry->d_parent->d_inode;
                                        p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
                                }
                                goto Proceed;
                        }
                        else
                                error = -ENOMEM;
                } else
                        error = -EEXIST;
        } else
                error = -ENOENT;
        goto Done;

 Proceed:
        if (init)
                error = init(inode);
        if (!error) {
                d_instantiate(dentry, inode);
                if (S_ISDIR(mode) || S_ISLNK(mode))
                        dget(dentry);  /* pin link and directory dentries in core */
        } else
                iput(inode);
 Done:
        return error;
}

/*
 * Get the name for corresponding element represented by the given configfs_dirent
 */
const unsigned char * configfs_get_name(struct configfs_dirent *sd)
{
        struct configfs_attribute *attr;

        BUG_ON(!sd || !sd->s_element);

        /* These always have a dentry, so use that */
        if (sd->s_type & (CONFIGFS_DIR | CONFIGFS_ITEM_LINK))
                return sd->s_dentry->d_name.name;

        if (sd->s_type & CONFIGFS_ITEM_ATTR) {
                attr = sd->s_element;
                return attr->ca_name;
        }
        return NULL;
}


/*
 * Unhashes the dentry corresponding to given configfs_dirent
 * Called with parent inode's i_mutex held.
 */
void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
{
        struct dentry * dentry = sd->s_dentry;

        if (dentry) {
                spin_lock(&dcache_lock);
                spin_lock(&dentry->d_lock);
                if (!(d_unhashed(dentry) && dentry->d_inode)) {
                        dget_locked(dentry);
                        __d_drop(dentry);
                        spin_unlock(&dentry->d_lock);
                        spin_unlock(&dcache_lock);
                        simple_unlink(parent->d_inode, dentry);
                } else {
                        spin_unlock(&dentry->d_lock);
                        spin_unlock(&dcache_lock);
                }
        }
}

void configfs_hash_and_remove(struct dentry * dir, const char * name)
{
        struct configfs_dirent * sd;
        struct configfs_dirent * parent_sd = dir->d_fsdata;

        if (dir->d_inode == NULL)
                /* no inode means this hasn't been made visible yet */
                return;

        mutex_lock(&dir->d_inode->i_mutex);
        list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
                if (!sd->s_element)
                        continue;
                if (!strcmp(configfs_get_name(sd), name)) {
                        list_del_init(&sd->s_sibling);
                        configfs_drop_dentry(sd, dir);
                        configfs_put(sd);
                        break;
                }
        }
        mutex_unlock(&dir->d_inode->i_mutex);
}

int __init configfs_inode_init(void)
{
        return bdi_init(&configfs_backing_dev_info);
}

void __exit configfs_inode_exit(void)
{
        bdi_destroy(&configfs_backing_dev_info);
}