Squashfs: block operations

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

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
new file mode 100644 (file)
index 0000000..c837dfc
--- /dev/null
+++ b/fs/squashfs/block.c
@@ -0,0 +1,274 @@
+/*
+ * 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.
+ *
+ * block.c
+ */
+
+/*
+ * This file implements the low-level routines to read and decompress
+ * datablocks and metadata blocks.
+ */
+
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/string.h>
+#include <linux/buffer_head.h>
+#include <linux/zlib.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs_fs_i.h"
+#include "squashfs.h"
+
+/*
+ * Read the metadata block length, this is stored in the first two
+ * bytes of the metadata block.
+ */
+static struct buffer_head *get_block_length(struct super_block *sb,
+                       u64 *cur_index, int *offset, int *length)
+{
+       struct squashfs_sb_info *msblk = sb->s_fs_info;
+       struct buffer_head *bh;
+
+       bh = sb_bread(sb, *cur_index);
+       if (bh == NULL)
+               return NULL;
+
+       if (msblk->devblksize - *offset == 1) {
+               *length = (unsigned char) bh->b_data[*offset];
+               put_bh(bh);
+               bh = sb_bread(sb, ++(*cur_index));
+               if (bh == NULL)
+                       return NULL;
+               *length |= (unsigned char) bh->b_data[0] << 8;
+               *offset = 1;
+       } else {
+               *length = (unsigned char) bh->b_data[*offset] |
+                       (unsigned char) bh->b_data[*offset + 1] << 8;
+               *offset += 2;
+       }
+
+       return bh;
+}
+
+
+/*
+ * Read and decompress a metadata block or datablock.  Length is non-zero
+ * if a datablock is being read (the size is stored elsewhere in the
+ * filesystem), otherwise the length is obtained from the first two bytes of
+ * the metadata block.  A bit in the length field indicates if the block
+ * is stored uncompressed in the filesystem (usually because compression
+ * generated a larger block - this does occasionally happen with zlib).
+ */
+int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
+                       int length, u64 *next_index, int srclength)
+{
+       struct squashfs_sb_info *msblk = sb->s_fs_info;
+       struct buffer_head **bh;
+       int offset = index & ((1 << msblk->devblksize_log2) - 1);
+       u64 cur_index = index >> msblk->devblksize_log2;
+       int bytes, compressed, b = 0, k = 0, page = 0, avail;
+
+
+       bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1,
+                               sizeof(*bh), GFP_KERNEL);
+       if (bh == NULL)
+               return -ENOMEM;
+
+       if (length) {
+               /*
+                * Datablock.
+                */
+               bytes = -offset;
+               compressed = SQUASHFS_COMPRESSED_BLOCK(length);
+               length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
+               if (next_index)
+                       *next_index = index + length;
+
+               TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
+                       index, compressed ? "" : "un", length, srclength);
+
+               if (length < 0 || length > srclength ||
+                               (index + length) > msblk->bytes_used)
+                       goto read_failure;
+
+               for (b = 0; bytes < length; b++, cur_index++) {
+                       bh[b] = sb_getblk(sb, cur_index);
+                       if (bh[b] == NULL)
+                               goto block_release;
+                       bytes += msblk->devblksize;
+               }
+               ll_rw_block(READ, b, bh);
+       } else {
+               /*
+                * Metadata block.
+                */
+               if ((index + 2) > msblk->bytes_used)
+                       goto read_failure;
+
+               bh[0] = get_block_length(sb, &cur_index, &offset, &length);
+               if (bh[0] == NULL)
+                       goto read_failure;
+               b = 1;
+
+               bytes = msblk->devblksize - offset;
+               compressed = SQUASHFS_COMPRESSED(length);
+               length = SQUASHFS_COMPRESSED_SIZE(length);
+               if (next_index)
+                       *next_index = index + length + 2;
+
+               TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
+                               compressed ? "" : "un", length);
+
+               if (length < 0 || length > srclength ||
+                                       (index + length) > msblk->bytes_used)
+                       goto block_release;
+
+               for (; bytes < length; b++) {
+                       bh[b] = sb_getblk(sb, ++cur_index);
+                       if (bh[b] == NULL)
+                               goto block_release;
+                       bytes += msblk->devblksize;
+               }
+               ll_rw_block(READ, b - 1, bh + 1);
+       }
+
+       if (compressed) {
+               int zlib_err = 0, zlib_init = 0;
+
+               /*
+                * Uncompress block.
+                */
+
+               mutex_lock(&msblk->read_data_mutex);
+
+               msblk->stream.avail_out = 0;
+               msblk->stream.avail_in = 0;
+
+               bytes = length;
+               do {
+                       if (msblk->stream.avail_in == 0 && k < b) {
+                               avail = min(bytes, msblk->devblksize - offset);
+                               bytes -= avail;
+                               wait_on_buffer(bh[k]);
+                               if (!buffer_uptodate(bh[k]))
+                                       goto release_mutex;
+
+                               if (avail == 0) {
+                                       offset = 0;
+                                       put_bh(bh[k++]);
+                                       continue;
+                               }
+
+                               msblk->stream.next_in = bh[k]->b_data + offset;
+                               msblk->stream.avail_in = avail;
+                               offset = 0;
+                       }
+
+                       if (msblk->stream.avail_out == 0) {
+                               msblk->stream.next_out = buffer[page++];
+                               msblk->stream.avail_out = PAGE_CACHE_SIZE;
+                       }
+
+                       if (!zlib_init) {
+                               zlib_err = zlib_inflateInit(&msblk->stream);
+                               if (zlib_err != Z_OK) {
+                                       ERROR("zlib_inflateInit returned"
+                                               " unexpected result 0x%x,"
+                                               " srclength %d\n", zlib_err,
+                                               srclength);
+                                       goto release_mutex;
+                               }
+                               zlib_init = 1;
+                       }
+
+                       zlib_err = zlib_inflate(&msblk->stream, Z_NO_FLUSH);
+
+                       if (msblk->stream.avail_in == 0 && k < b)
+                               put_bh(bh[k++]);
+               } while (zlib_err == Z_OK);
+
+               if (zlib_err != Z_STREAM_END) {
+                       ERROR("zlib_inflate returned unexpected result"
+                               " 0x%x, srclength %d, avail_in %d,"
+                               " avail_out %d\n", zlib_err, srclength,
+                               msblk->stream.avail_in,
+                               msblk->stream.avail_out);
+                       goto release_mutex;
+               }
+
+               zlib_err = zlib_inflateEnd(&msblk->stream);
+               if (zlib_err != Z_OK) {
+                       ERROR("zlib_inflateEnd returned unexpected result 0x%x,"
+                               " srclength %d\n", zlib_err, srclength);
+                       goto release_mutex;
+               }
+               length = msblk->stream.total_out;
+               mutex_unlock(&msblk->read_data_mutex);
+       } else {
+               /*
+                * Block is uncompressed.
+                */
+               int i, in, pg_offset = 0;
+
+               for (i = 0; i < b; i++) {
+                       wait_on_buffer(bh[i]);
+                       if (!buffer_uptodate(bh[i]))
+                               goto block_release;
+               }
+
+               for (bytes = length; k < b; k++) {
+                       in = min(bytes, msblk->devblksize - offset);
+                       bytes -= in;
+                       while (in) {
+                               if (pg_offset == PAGE_CACHE_SIZE) {
+                                       page++;
+                                       pg_offset = 0;
+                               }
+                               avail = min_t(int, in, PAGE_CACHE_SIZE -
+                                               pg_offset);
+                               memcpy(buffer[page] + pg_offset,
+                                               bh[k]->b_data + offset, avail);
+                               in -= avail;
+                               pg_offset += avail;
+                               offset += avail;
+                       }
+                       offset = 0;
+                       put_bh(bh[k]);
+               }
+       }
+
+       kfree(bh);
+       return length;
+
+release_mutex:
+       mutex_unlock(&msblk->read_data_mutex);
+
+block_release:
+       for (; k < b; k++)
+               put_bh(bh[k]);
+
+read_failure:
+       ERROR("sb_bread failed reading block 0x%llx\n", cur_index);
+       kfree(bh);
+       return -EIO;
+}