Squashfs: export operations
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
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Phillip Lougher
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0aa6661905
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122601408d
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/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@lougher.demon.co.uk>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2,
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* or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* export.c
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*/
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/*
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* This file implements code to make Squashfs filesystems exportable (NFS etc.)
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*
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* The export code uses an inode lookup table to map inode numbers passed in
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* filehandles to an inode location on disk. This table is stored compressed
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* into metadata blocks. A second index table is used to locate these. This
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* second index table for speed of access (and because it is small) is read at
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* mount time and cached in memory.
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*
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* The inode lookup table is used only by the export code, inode disk
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* locations are directly encoded in directories, enabling direct access
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* without an intermediate lookup for all operations except the export ops.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/dcache.h>
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#include <linux/exportfs.h>
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#include <linux/zlib.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs_fs_i.h"
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#include "squashfs.h"
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/*
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* Look-up inode number (ino) in table, returning the inode location.
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*/
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static long long squashfs_inode_lookup(struct super_block *sb, int ino_num)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1);
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int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1);
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u64 start = le64_to_cpu(msblk->inode_lookup_table[blk]);
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__le64 ino;
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int err;
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TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num);
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err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));
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if (err < 0)
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return err;
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TRACE("squashfs_inode_lookup, inode = 0x%llx\n",
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(u64) le64_to_cpu(ino));
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return le64_to_cpu(ino);
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}
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static struct dentry *squashfs_export_iget(struct super_block *sb,
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unsigned int ino_num)
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{
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long long ino;
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struct dentry *dentry = ERR_PTR(-ENOENT);
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TRACE("Entered squashfs_export_iget\n");
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ino = squashfs_inode_lookup(sb, ino_num);
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if (ino >= 0)
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dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num));
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return dentry;
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}
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static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,
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struct fid *fid, int fh_len, int fh_type)
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{
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if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)
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|| fh_len < 2)
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return NULL;
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return squashfs_export_iget(sb, fid->i32.ino);
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}
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static struct dentry *squashfs_fh_to_parent(struct super_block *sb,
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struct fid *fid, int fh_len, int fh_type)
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{
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if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)
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return NULL;
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return squashfs_export_iget(sb, fid->i32.parent_ino);
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}
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static struct dentry *squashfs_get_parent(struct dentry *child)
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{
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struct inode *inode = child->d_inode;
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unsigned int parent_ino = squashfs_i(inode)->parent;
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return squashfs_export_iget(inode->i_sb, parent_ino);
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}
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/*
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* Read uncompressed inode lookup table indexes off disk into memory
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*/
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__le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
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u64 lookup_table_start, unsigned int inodes)
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{
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unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);
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__le64 *inode_lookup_table;
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int err;
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TRACE("In read_inode_lookup_table, length %d\n", length);
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/* Allocate inode lookup table indexes */
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inode_lookup_table = kmalloc(length, GFP_KERNEL);
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if (inode_lookup_table == NULL) {
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ERROR("Failed to allocate inode lookup table\n");
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return ERR_PTR(-ENOMEM);
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}
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err = squashfs_read_table(sb, inode_lookup_table, lookup_table_start,
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length);
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if (err < 0) {
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ERROR("unable to read inode lookup table\n");
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kfree(inode_lookup_table);
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return ERR_PTR(err);
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}
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return inode_lookup_table;
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}
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const struct export_operations squashfs_export_ops = {
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.fh_to_dentry = squashfs_fh_to_dentry,
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.fh_to_parent = squashfs_fh_to_parent,
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.get_parent = squashfs_get_parent
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};
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