Squashfs: block operations

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

1 files changed, 274 insertions, 0 deletions

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
new file mode 100644
index 000000000000..c837dfc2b3c6
--- /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;
+}