Subject: [PATCH 03/16] Squashfs: directory readdir operations

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Signed-off-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxxxxxx>
---
 fs/squashfs/dir.c |  230 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 230 insertions(+), 0 deletions(-)

diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c
new file mode 100644
index 0000000..c27c9c4
--- /dev/null
+++ b/fs/squashfs/dir.c
@@ -0,0 +1,230 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ * Phillip Lougher <phillip@xxxxxxxxxxxxxxxxxxx>
+ *
+ * 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.
+ *
+ * dir.c
+ */
+
+/*
+ * This file implements code to read directories from disk.
+ *
+ * See namei.c for a description of directory organisation on disk.
+ */
+
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/slab.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"
+
+static const unsigned char squashfs_filetype_table[] = {
+	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
+};
+
+/*
+ * Lookup offset (f_pos) in the directory index, returning the
+ * metadata block containing it.
+ */
+static int get_dir_index_using_offset(struct super_block *s,
+	long long *next_block, unsigned int *next_offset,
+	long long index_start, unsigned int index_offset, int i_count,
+	long long f_pos)
+{
+	struct squashfs_sb_info *msblk = s->s_fs_info;
+	int i, index, length = 0;
+	struct squashfs_dir_index dir_index;
+
+	TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
+					i_count, f_pos);
+
+	/*
+	 * Translate from external f_pos to the internal f_pos.  This
+	 * is offset by 3 because we invent "." and ".." entries which are
+	 * not actually stored in the directory.
+	 */
+	f_pos -= 3;
+	if (f_pos == 0)
+		goto finish;
+
+	for (i = 0; i < i_count; i++) {
+		squashfs_read_metadata(s, &dir_index, index_start,
+					index_offset, sizeof(dir_index),
+					&index_start, &index_offset);
+
+		index = le32_to_cpu(dir_index.index);
+		if (index > f_pos)
+			break;
+
+		squashfs_read_metadata(s, NULL, index_start, index_offset,
+					le32_to_cpu(dir_index.size) + 1,
+					&index_start, &index_offset);
+
+		length = index;
+		*next_block = le32_to_cpu(dir_index.start_block) +
+					msblk->directory_table_start;
+	}
+
+	*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
+
+finish:
+	/*
+	 * Translate back from internal f_pos to external f_pos.
+	 */
+	return length + 3;
+}
+
+
+static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir)
+{
+	struct inode *i = file->f_dentry->d_inode;
+	struct squashfs_sb_info *msblk = i->i_sb->s_fs_info;
+	long long next_block = SQUASHFS_I(i)->start_block +
+				msblk->directory_table_start;
+	int next_offset = SQUASHFS_I(i)->offset, length = 0, dir_count, size,
+				type;
+	unsigned int inode_number;
+	struct squashfs_dir_header dirh;
+	struct squashfs_dir_entry *dire;
+
+	TRACE("Entered squashfs_readdir [%llx:%x]\n", next_block, next_offset);
+
+	dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
+	if (dire == NULL) {
+		ERROR("Failed to allocate squashfs_dir_entry\n");
+		goto finish;
+	}
+
+	/*
+	 * Return "." and  ".." entries as the first two filenames in the
+	 * directory.  To maximise compression these two entries are not
+	 * stored in the directory, and so we invent them here.
+	 *
+	 * It also means that the external f_pos is offset by 3 from the
+	 * on-disk directory f_pos.
+	 */
+	while (file->f_pos < 3) {
+		char *name;
+		int size, i_ino;
+
+		if (file->f_pos == 0) {
+			name = ".";
+			size = 1;
+			i_ino = i->i_ino;
+		} else {
+			name = "..";
+			size = 2;
+			i_ino = SQUASHFS_I(i)->parent_inode;
+		}
+
+		TRACE("Calling filldir(%p, %s, %d, %lld, %d, %d)\n",
+				dirent, name, size, file->f_pos, i_ino,
+				squashfs_filetype_table[1]);
+
+		if (filldir(dirent, name, size, file->f_pos, i_ino,
+				squashfs_filetype_table[1]) < 0) {
+				TRACE("Filldir returned less than 0\n");
+			goto finish;
+		}
+
+		file->f_pos += size;
+	}
+
+	length = get_dir_index_using_offset(i->i_sb, &next_block, &next_offset,
+				SQUASHFS_I(i)->dir_index_start,
+				SQUASHFS_I(i)->dir_index_offset,
+				SQUASHFS_I(i)->dir_index_count,
+				file->f_pos);
+
+	while (length < i_size_read(i)) {
+		/*
+		 * Read directory header
+		 */
+		if (!squashfs_read_metadata(i->i_sb, &dirh, next_block,
+				next_offset, sizeof(dirh), &next_block,
+				&next_offset))
+			goto failed_read;
+
+		length += sizeof(dirh);
+
+		dir_count = le32_to_cpu(dirh.count) + 1;
+		while (dir_count--) {
+			/*
+			 * Read directory entry.
+			 */
+			if (!squashfs_read_metadata(i->i_sb, dire, next_block,
+					next_offset, sizeof(*dire),
+					&next_block, &next_offset))
+				goto failed_read;
+
+			size = le16_to_cpu(dire->size) + 1;
+
+			if (!squashfs_read_metadata(i->i_sb, dire->name,
+					next_block, next_offset, size,
+					&next_block, &next_offset))
+				goto failed_read;
+
+			length += sizeof(*dire) + size;
+
+			if (file->f_pos >= length)
+				continue;
+
+			dire->name[size] = '\0';
+			inode_number = le32_to_cpu(dirh.inode_number) +
+				((short) le16_to_cpu(dire->inode_number));
+			type = le16_to_cpu(dire->type);
+
+			TRACE("Calling filldir(%p, %s, %d, %lld, %x:%x, %d, %d)"
+					"\n", dirent, dire->name, size,
+					file->f_pos,
+					le32_to_cpu(dirh.start_block),
+					le16_to_cpu(dire->offset),
+					inode_number,
+					squashfs_filetype_table[type]);
+
+			if (filldir(dirent, dire->name, size, file->f_pos,
+					inode_number,
+					squashfs_filetype_table[type]) < 0) {
+				TRACE("Filldir returned less than 0\n");
+				goto finish;
+			}
+
+			file->f_pos = length;
+		}
+	}
+
+finish:
+	kfree(dire);
+	return 0;
+
+failed_read:
+	ERROR("Unable to read directory block [%llx:%x]\n", next_block,
+		next_offset);
+	kfree(dire);
+	return 0;
+}
+
+
+const struct file_operations squashfs_dir_ops = {
+	.read = generic_read_dir,
+	.readdir = squashfs_readdir
+};
-- 
1.5.2.5

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