/* * 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. * * export.c */ /* * This file implements code to make Squashfs filesystems exportable (NFS etc.) * * The export code uses an inode lookup table to map inode numbers passed in * filehandles to an inode location on disk. 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. * * The inode lookup table is used only by the export code, inode disk * locations are directly encoded in directories, enabling direct access * without an intermediate lookup for all operations except the export ops. */ #include <linux/fs.h> #include <linux/vfs.h> #include <linux/dcache.h> #include <linux/exportfs.h> #include <linux/zlib.h> #include <linux/slab.h> #include "squashfs_fs.h" #include "squashfs_fs_sb.h" #include "squashfs_fs_i.h" #include "squashfs.h" /* * Look-up inode number (ino) in table, returning the inode location. */ static long long squashfs_inode_lookup(struct super_block *sb, int ino_num) { struct squashfs_sb_info *msblk = sb->s_fs_info; int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1); int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1); u64 start = le64_to_cpu(msblk->inode_lookup_table[blk]); __le64 ino; int err; TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino)); if (err < 0) return err; TRACE("squashfs_inode_lookup, inode = 0x%llx\n", (u64) le64_to_cpu(ino)); return le64_to_cpu(ino); } static struct dentry *squashfs_export_iget(struct super_block *sb, unsigned int ino_num) { long long ino; struct dentry *dentry = ERR_PTR(-ENOENT); TRACE("Entered squashfs_export_iget\n"); ino = squashfs_inode_lookup(sb, ino_num); if (ino >= 0) dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); return dentry; } static struct dentry *squashfs_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len, int fh_type) { if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT) || fh_len < 2) return NULL; return squashfs_export_iget(sb, fid->i32.ino); } static struct dentry *squashfs_fh_to_parent(struct super_block *sb, struct fid *fid, int fh_len, int fh_type) { if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4) return NULL; return squashfs_export_iget(sb, fid->i32.parent_ino); } static struct dentry *squashfs_get_parent(struct dentry *child) { struct inode *inode = child->d_inode; unsigned int parent_ino = squashfs_i(inode)->parent; return squashfs_export_iget(inode->i_sb, parent_ino); } /* * Read uncompressed inode lookup table indexes off disk into memory */ __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, u64 lookup_table_start, unsigned int inodes) { unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); __le64 *inode_lookup_table; int err; TRACE("In read_inode_lookup_table, length %d\n", length); /* Allocate inode lookup table indexes */ inode_lookup_table = kmalloc(length, GFP_KERNEL); if (inode_lookup_table == NULL) { ERROR("Failed to allocate inode lookup table\n"); return ERR_PTR(-ENOMEM); } err = squashfs_read_table(sb, inode_lookup_table, lookup_table_start, length); if (err < 0) { ERROR("unable to read inode lookup table\n"); kfree(inode_lookup_table); return ERR_PTR(err); } return inode_lookup_table; } const struct export_operations squashfs_export_ops = { .fh_to_dentry = squashfs_fh_to_dentry, .fh_to_parent = squashfs_fh_to_parent, .get_parent = squashfs_get_parent };