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

[Phillip Lougher <phillip@lougher.demon.co.uk>]

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
---
 fs/squashfs/export.c |  146 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 146 insertions(+), 0 deletions(-)

diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c
new file mode 100644
index 0000000..0a7a98a
--- /dev/null
+++ b/fs/squashfs/export.c
@@ -0,0 +1,146 @@
+/*
+ * 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/squashfs_fs.h>
+#include <linux/squashfs_fs_sb.h>
+#include <linux/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 *s, int ino)
+{
+	struct squashfs_sb_info *msblk = s->s_fs_info;
+	int blk = SQUASHFS_LOOKUP_BLOCK(ino - 1);
+	int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino - 1);
+	long long start = le64_to_cpu(msblk->inode_lookup_table[blk]);
+	__le64 inode;
+
+	TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino);
+
+	if (!squashfs_read_metadata(s, &inode, start, offset,
+					sizeof(inode), &start, &offset))
+		return SQUASHFS_INVALID_BLK;
+
+	TRACE("squashfs_inode_lookup, inode = 0x%llx\n", le64_to_cpu(inode));
+	return le64_to_cpu(inode);
+}
+
+
+static struct dentry *squashfs_export_iget(struct super_block *s,
+	unsigned int inode_number)
+{
+	long long inode;
+	struct dentry *dentry = ERR_PTR(-ENOENT);
+
+	TRACE("Entered squashfs_export_iget\n");
+
+	inode = squashfs_inode_lookup(s, inode_number);
+	if (inode != SQUASHFS_INVALID_BLK)
+		dentry = d_obtain_alias(squashfs_iget(s, inode, inode_number));
+
+	return dentry;
+}
+
+
+static struct dentry *squashfs_fh_to_dentry(struct super_block *s,
+		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(s, fid->i32.ino);
+}
+
+
+static struct dentry *squashfs_fh_to_parent(struct super_block *s,
+		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(s, fid->i32.parent_ino);
+}
+
+
+static struct dentry *squashfs_get_parent(struct dentry *child)
+{
+	struct inode *i = child->d_inode;
+
+	return squashfs_export_iget(i->i_sb, SQUASHFS_I(i)->parent_inode);
+}
+
+
+__le64 *read_inode_lookup_table(struct super_block *s,
+		long long lookup_table_start, unsigned int inodes)
+{
+	unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);
+	__le64 *inode_lookup_table;
+
+	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 NULL;
+	}
+
+	if (!squashfs_read_data(s, inode_lookup_table, lookup_table_start,
+			length | SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, length)) {
+		ERROR("unable to read inode lookup table\n");
+		kfree(inode_lookup_table);
+		return NULL;
+	}
+
+	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