Squashfs: export operations

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c
new file mode 100644 (file)
index 0000000..69e971d
--- /dev/null
+++ b/fs/squashfs/export.c
@@ -0,0 +1,155 @@
+/*
+ * 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);
+       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
+};