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| -rw-r--r-- | fs/squashfs/id.c | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/fs/squashfs/id.c b/fs/squashfs/id.c new file mode 100644 index 000000000000..3795b837ba28 --- /dev/null +++ b/fs/squashfs/id.c @@ -0,0 +1,94 @@ +/* + * 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; +} |