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Diffstat (limited to 'kernel/fs/squashfs/export.c')
| -rw-r--r-- | kernel/fs/squashfs/export.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/kernel/fs/squashfs/export.c b/kernel/fs/squashfs/export.c new file mode 100644 index 000000000..8073b6532 --- /dev/null +++ b/kernel/fs/squashfs/export.c @@ -0,0 +1,163 @@ +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + * Phillip Lougher <phillip@squashfs.org.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/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 = d_inode(child); + 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, u64 next_table, unsigned int inodes) +{ + unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); + __le64 *table; + + TRACE("In read_inode_lookup_table, length %d\n", length); + + /* Sanity check values */ + + /* there should always be at least one inode */ + if (inodes == 0) + return ERR_PTR(-EINVAL); + + /* length bytes should not extend into the next table - this check + * also traps instances where lookup_table_start is incorrectly larger + * than the next table start + */ + if (lookup_table_start + length > next_table) + return ERR_PTR(-EINVAL); + + table = squashfs_read_table(sb, lookup_table_start, length); + + /* + * table[0] points to the first inode lookup table metadata block, + * this should be less than lookup_table_start + */ + if (!IS_ERR(table) && le64_to_cpu(table[0]) >= lookup_table_start) { + kfree(table); + return ERR_PTR(-EINVAL); + } + + return 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 +}; |