/* fs/fat/nfs.c
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 *
 */

#include <linux/exportfs.h>
#include "fat.h"

/**
 * Look up a directory inode given its starting cluster.
 */
static struct inode *fat_dget(struct super_block *sb, int i_logstart)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct hlist_head *head;
	struct msdos_inode_info *i;
	struct inode *inode = NULL;

	head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
	spin_lock(&sbi->dir_hash_lock);
	hlist_for_each_entry(i, head, i_dir_hash) {
		BUG_ON(i->vfs_inode.i_sb != sb);
		if (i->i_logstart != i_logstart)
			continue;
		inode = igrab(&i->vfs_inode);
		if (inode)
			break;
	}
	spin_unlock(&sbi->dir_hash_lock);
	return inode;
}

static struct inode *fat_nfs_get_inode(struct super_block *sb,
				       u64 ino, u32 generation)
{
	struct inode *inode;

	if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
		return NULL;

	inode = ilookup(sb, ino);
	if (inode && generation && (inode->i_generation != generation)) {
		iput(inode);
		inode = NULL;
	}

	return inode;
}

/**
 * Map a NFS file handle to a corresponding dentry.
 * The dentry may or may not be connected to the filesystem root.
 */
struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
				int fh_len, int fh_type)
{
	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
				    fat_nfs_get_inode);
}

/*
 * Find the parent for a file specified by NFS handle.
 * This requires that the handle contain the i_ino of the parent.
 */
struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
				int fh_len, int fh_type)
{
	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
				    fat_nfs_get_inode);
}

/*
 * Find the parent for a directory that is not currently connected to
 * the filesystem root.
 *
 * On entry, the caller holds child_dir->d_inode->i_mutex.
 */
struct dentry *fat_get_parent(struct dentry *child_dir)
{
	struct super_block *sb = child_dir->d_sb;
	struct buffer_head *bh = NULL;
	struct msdos_dir_entry *de;
	struct inode *parent_inode = NULL;

	if (!fat_get_dotdot_entry(child_dir->d_inode, &bh, &de)) {
		int parent_logstart = fat_get_start(MSDOS_SB(sb), de);
		parent_inode = fat_dget(sb, parent_logstart);
	}
	brelse(bh);

	return d_obtain_alias(parent_inode);
}