Date:	Fri, 17 Oct 2008 16:42:51 +0100
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: Subject: [PATCH 11/16] Squashfs: block operations


Signed-off-by: Phillip Lougher <phillip@...gher.demon.co.uk>
---
 fs/squashfs/block.c |  257 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 257 insertions(+), 0 deletions(-)

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
new file mode 100644
index 0000000..0d1a74d
--- /dev/null
+++ b/fs/squashfs/block.c
@@ -0,0 +1,257 @@
+/*
+ * 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.
+ *
+ * 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 <linux/squashfs_fs.h>
+#include <linux/squashfs_fs_sb.h>
+#include <linux/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 *s,
+			int *cur_index, int *offset, unsigned int *length)
+{
+	struct squashfs_sb_info *msblk = s->s_fs_info;
+	struct buffer_head *bh;
+
+	bh = sb_bread(s, *cur_index);
+	if (bh == NULL)
+		goto out;
+
+	if (msblk->devblksize - *offset == 1) {
+		*length = (unsigned char) bh->b_data[*offset];
+		brelse(bh);
+		bh = sb_bread(s, ++(*cur_index));
+		if (bh == NULL)
+			goto out;
+		*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;
+	}
+
+out:
+	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).
+ */
+unsigned int squashfs_read_data(struct super_block *s, void *buffer,
+			long long index, unsigned int length,
+			long long *next_index, int srclength)
+{
+	struct squashfs_sb_info *msblk = s->s_fs_info;
+	struct buffer_head **bh;
+	unsigned int offset = index & ((1 << msblk->devblksize_log2) - 1);
+	unsigned int cur_index = index >> msblk->devblksize_log2;
+	int bytes, avail, b = 0, k = 0;
+	unsigned int compressed;
+	unsigned int c_byte = length;
+
+	bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1,
+				sizeof(*bh), GFP_KERNEL);
+	if (bh == NULL)
+		goto read_failure;
+
+	if (c_byte) {
+		/*
+		 * Datablock.
+		 */
+		bytes = -offset;
+		compressed = SQUASHFS_COMPRESSED_BLOCK(c_byte);
+		c_byte = SQUASHFS_COMPRESSED_SIZE_BLOCK(c_byte);
+
+		TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
+			index, compressed ? "" : "un", c_byte, srclength);
+
+		if (c_byte > srclength || index < 0 ||
+				(index + c_byte) > msblk->bytes_used)
+			goto read_failure;
+
+		for (b = 0; bytes < (int) c_byte; b++, cur_index++) {
+			bh[b] = sb_getblk(s, cur_index);
+			if (bh[b] == NULL)
+				goto block_release;
+			bytes += msblk->devblksize;
+		}
+		ll_rw_block(READ, b, bh);
+	} else {
+		/*
+		 * Metadata block.
+		 */
+		if (index < 0 || (index + 2) > msblk->bytes_used)
+			goto read_failure;
+
+		bh[0] = get_block_length(s, &cur_index, &offset, &c_byte);
+		if (bh[0] == NULL)
+			goto read_failure;
+		b = 1;
+
+		bytes = msblk->devblksize - offset;
+		compressed = SQUASHFS_COMPRESSED(c_byte);
+		c_byte = SQUASHFS_COMPRESSED_SIZE(c_byte);
+
+		TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
+				compressed ? "" : "un", c_byte);
+
+		if (c_byte > srclength || (index + c_byte) > msblk->bytes_used)
+			goto block_release;
+
+		for (; bytes < c_byte; b++) {
+			bh[b] = sb_getblk(s, ++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;
+
+		/*
+		 * Uncompress block.
+		 */
+
+		mutex_lock(&msblk->read_data_mutex);
+
+		msblk->stream.next_out = buffer;
+		msblk->stream.avail_out = srclength;
+
+		for (bytes = 0; k < b; k++) {
+			avail = min(c_byte - bytes, msblk->devblksize - offset);
+
+			wait_on_buffer(bh[k]);
+			if (!buffer_uptodate(bh[k]))
+				goto release_mutex;
+
+			msblk->stream.next_in = bh[k]->b_data + offset;
+			msblk->stream.avail_in = avail;
+
+			if (k == 0) {
+				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;
+				}
+
+				if (avail == 0) {
+					offset = 0;
+					brelse(bh[k]);
+					continue;
+				}
+			}
+
+			zlib_err = zlib_inflate(&msblk->stream, Z_NO_FLUSH);
+			if (zlib_err != Z_OK && 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;
+			}
+
+			bytes += avail;
+			offset = 0;
+			brelse(bh[k]);
+		}
+
+		if (zlib_err != Z_STREAM_END)
+			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;
+		}
+		bytes = msblk->stream.total_out;
+		mutex_unlock(&msblk->read_data_mutex);
+	} else {
+		/*
+		 * Block is uncompressed.
+		 */
+		int i;
+
+		for (i = 0; i < b; i++) {
+			wait_on_buffer(bh[i]);
+			if (!buffer_uptodate(bh[i]))
+				goto block_release;
+		}
+
+		for (bytes = 0; k < b; k++) {
+			avail = min(c_byte - bytes, msblk->devblksize - offset);
+
+			memcpy(buffer + bytes, bh[k]->b_data + offset, avail);
+			bytes += avail;
+			offset = 0;
+			brelse(bh[k]);
+		}
+	}
+
+	if (next_index)
+		*next_index = index + c_byte + (length ? 0 : 2);
+
+	kfree(bh);
+	return bytes;
+
+release_mutex:
+	mutex_unlock(&msblk->read_data_mutex);
+
+block_release:
+	for (; k < b; k++)
+		brelse(bh[k]);
+
+read_failure:
+	ERROR("sb_bread failed reading block 0x%x\n", cur_index);
+	kfree(bh);
+	return 0;
+}
-- 
1.5.2.5

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