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    Subject[PATCH V2 07/16] Squashfs: export operations
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    Date

    Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
    ---
    fs/squashfs/export.c | 152 ++++++++++++++++++++++++++++++++++++++++++++++++++
    1 files changed, 152 insertions(+), 0 deletions(-)

    diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c
    new file mode 100644
    index 0000000..6ba8724
    --- /dev/null
    +++ b/fs/squashfs/export.c
    @@ -0,0 +1,152 @@
    +/*
    + * 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 "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);
    + long long 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",
    + (unsigned long long) 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);
    +}
    +
    +
    +__le64 *read_inode_lookup_table(struct super_block *sb,
    + long long 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 */
    + 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_data(sb, inode_lookup_table, lookup_table_start,
    + length | SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, 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
    +};
    --
    1.5.2.5


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