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Date: Wed, 29 Oct 2008 01:49:55 +0000
From: Phillip Lougher <phillip@...gher.demon.co.uk>
To: akpm@...ux-foundation.org, linux-embedded@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
tim.bird@...sony.com
Subject: [PATCH V2 03/16] Squashfs: directory readdir operations
Signed-off-by: Phillip Lougher <phillip@...gher.demon.co.uk>
---
fs/squashfs/dir.c | 236 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 236 insertions(+), 0 deletions(-)
diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c
new file mode 100644
index 0000000..f5564e5
--- /dev/null
+++ b/fs/squashfs/dir.c
@@ -0,0 +1,236 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ * Phillip Lougher <phillip@...gher.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.
+ *
+ * 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 "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "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.
+ *
+ * If we get an error reading the index then return the part of the index
+ * (if any) we have managed to read - the index isn't essential, just
+ * quicker.
+ */
+static int get_dir_index_using_offset(struct super_block *sb,
+ long long *next_block, int *next_offset,
+ long long index_start, int index_offset, int i_count,
+ long long f_pos)
+{
+ struct squashfs_sb_info *msblk = sb->s_fs_info;
+ int err, 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.
+ */
+ if (f_pos < 3)
+ return f_pos;
+ f_pos -= 3;
+
+ for (i = 0; i < i_count; i++) {
+ err = squashfs_read_metadata(sb, &dir_index, &index_start,
+ &index_offset, sizeof(dir_index));
+ if (err < 0)
+ break;
+
+ index = le32_to_cpu(dir_index.index);
+ if (index > f_pos)
+ /*
+ * Found the index we're looking for.
+ */
+ break;
+
+ err = squashfs_read_metadata(sb, NULL, &index_start,
+ &index_offset, le32_to_cpu(dir_index.size) + 1);
+ if (err < 0)
+ break;
+
+ length = index;
+ *next_block = le32_to_cpu(dir_index.start_block) +
+ msblk->directory_table;
+ }
+
+ *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
+
+ /*
+ * 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 *inode = file->f_dentry->d_inode;
+ struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
+ long long block = SQUASHFS_I(inode)->start + msblk->directory_table;
+ int offset = SQUASHFS_I(inode)->offset, length = 0, dir_count, size,
+ type, err;
+ unsigned int inode_number;
+ struct squashfs_dir_header dirh;
+ struct squashfs_dir_entry *dire;
+
+ TRACE("Entered squashfs_readdir [%llx:%x]\n", block, 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 i_ino;
+
+ if (file->f_pos == 0) {
+ name = ".";
+ size = 1;
+ i_ino = inode->i_ino;
+ } else {
+ name = "..";
+ size = 2;
+ i_ino = SQUASHFS_I(inode)->parent;
+ }
+
+ 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(inode->i_sb, &block, &offset,
+ SQUASHFS_I(inode)->dir_idx_start,
+ SQUASHFS_I(inode)->dir_idx_offset,
+ SQUASHFS_I(inode)->dir_idx_cnt,
+ file->f_pos);
+
+ while (length < i_size_read(inode)) {
+ /*
+ * Read directory header
+ */
+ err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
+ &offset, sizeof(dirh));
+ if (err < 0)
+ goto failed_read;
+
+ length += sizeof(dirh);
+
+ dir_count = le32_to_cpu(dirh.count) + 1;
+ while (dir_count--) {
+ /*
+ * Read directory entry.
+ */
+ err = squashfs_read_metadata(inode->i_sb, dire, &block,
+ &offset, sizeof(*dire));
+ if (err < 0)
+ goto failed_read;
+
+ size = le16_to_cpu(dire->size) + 1;
+
+ err = squashfs_read_metadata(inode->i_sb, dire->name,
+ &block, &offset, size);
+ if (err < 0)
+ 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", block, 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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