Squashfs: directory readdir operations

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

diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c
new file mode 100644 (file)
index 0000000..566b0ea
--- /dev/null
+++ b/fs/squashfs/dir.c
@@ -0,0 +1,235 @@
+/*
+ * 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.
+ *
+ * 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,
+       u64 *next_block, int *next_offset, u64 index_start, int index_offset,
+       int i_count, u64 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;
+       u64 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
+};