Squashfs: directory readdir operations

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

1 files changed, 235 insertions, 0 deletions

diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c
new file mode 100644
index 000000000000..566b0eaed868
--- /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
+};