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Squashfs: uid/gid lookup operations

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Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
This commit is contained in:
Phillip Lougher 2009-01-05 08:46:26 +00:00
parent 122edd1514
commit 8256c8f631
1 changed files with 94 additions and 0 deletions
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fs/squashfs/id.c Normal file
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/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
* Phillip Lougher <phillip@lougher.demon.co.uk>
*
* 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,
* 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* id.c
*/
/*
* This file implements code to handle uids and gids.
*
* For space efficiency regular files store uid and gid indexes, which are
* converted to 32-bit uids/gids using an id look up table. This table is
* stored compressed into metadata blocks. A second index table is used to
* locate these. This second index table for speed of access (and because it
* is small) is read at mount time and cached in memory.
*/
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/zlib.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
/*
* Map uid/gid index into real 32-bit uid/gid using the id look up table
*/
int squashfs_get_id(struct super_block *sb, unsigned int index,
unsigned int *id)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
int block = SQUASHFS_ID_BLOCK(index);
int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
u64 start_block = le64_to_cpu(msblk->id_table[block]);
__le32 disk_id;
int err;
err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
sizeof(disk_id));
if (err < 0)
return err;
*id = le32_to_cpu(disk_id);
return 0;
}
/*
* Read uncompressed id lookup table indexes from disk into memory
*/
__le64 *squashfs_read_id_index_table(struct super_block *sb,
u64 id_table_start, unsigned short no_ids)
{
unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
__le64 *id_table;
int err;
TRACE("In read_id_index_table, length %d\n", length);
/* Allocate id lookup table indexes */
id_table = kmalloc(length, GFP_KERNEL);
if (id_table == NULL) {
ERROR("Failed to allocate id index table\n");
return ERR_PTR(-ENOMEM);
}
err = squashfs_read_table(sb, id_table, id_table_start, length);
if (err < 0) {
ERROR("unable to read id index table\n");
kfree(id_table);
return ERR_PTR(err);
}
return id_table;
}