diff options
Diffstat (limited to 'fs/isofs/compress.c')
| -rw-r--r-- | fs/isofs/compress.c | 393 |
1 files changed, 393 insertions, 0 deletions
diff --git a/fs/isofs/compress.c b/fs/isofs/compress.c new file mode 100644 index 000000000..10205ecec --- /dev/null +++ b/fs/isofs/compress.c @@ -0,0 +1,393 @@ +/* -*- linux-c -*- ------------------------------------------------------- * + * + * Copyright 2001 H. Peter Anvin - All Rights Reserved + * + * 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, Inc., 675 Mass Ave, Cambridge MA 02139, + * USA; either version 2 of the License, or (at your option) any later + * version; incorporated herein by reference. + * + * ----------------------------------------------------------------------- */ + +/* + * linux/fs/isofs/compress.c + * + * Transparent decompression of files on an iso9660 filesystem + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/bio.h> + +#include <linux/slab.h> +#include <linux/vmalloc.h> +#include <linux/zlib.h> + +#include "isofs.h" +#include "zisofs.h" + +/* This should probably be global. */ +static char zisofs_sink_page[PAGE_SIZE]; + +/* + * This contains the zlib memory allocation and the mutex for the + * allocation; this avoids failures at block-decompression time. + */ +static void *zisofs_zlib_workspace; +static DEFINE_MUTEX(zisofs_zlib_lock); + +/* + * Read data of @inode from @block_start to @block_end and uncompress + * to one zisofs block. Store the data in the @pages array with @pcount + * entries. Start storing at offset @poffset of the first page. + */ +static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start, + loff_t block_end, int pcount, + struct page **pages, unsigned poffset, + int *errp) +{ + unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1]; + unsigned int bufsize = ISOFS_BUFFER_SIZE(inode); + unsigned int bufshift = ISOFS_BUFFER_BITS(inode); + unsigned int bufmask = bufsize - 1; + int i, block_size = block_end - block_start; + z_stream stream = { .total_out = 0, + .avail_in = 0, + .avail_out = 0, }; + int zerr; + int needblocks = (block_size + (block_start & bufmask) + bufmask) + >> bufshift; + int haveblocks; + blkcnt_t blocknum; + struct buffer_head **bhs; + int curbh, curpage; + + if (block_size > deflateBound(1UL << zisofs_block_shift)) { + *errp = -EIO; + return 0; + } + /* Empty block? */ + if (block_size == 0) { + for ( i = 0 ; i < pcount ; i++ ) { + if (!pages[i]) + continue; + memset(page_address(pages[i]), 0, PAGE_SIZE); + flush_dcache_page(pages[i]); + SetPageUptodate(pages[i]); + } + return ((loff_t)pcount) << PAGE_SHIFT; + } + + /* Because zlib is not thread-safe, do all the I/O at the top. */ + blocknum = block_start >> bufshift; + bhs = kcalloc(needblocks + 1, sizeof(*bhs), GFP_KERNEL); + if (!bhs) { + *errp = -ENOMEM; + return 0; + } + haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks); + ll_rw_block(REQ_OP_READ, 0, haveblocks, bhs); + + curbh = 0; + curpage = 0; + /* + * First block is special since it may be fractional. We also wait for + * it before grabbing the zlib mutex; odds are that the subsequent + * blocks are going to come in in short order so we don't hold the zlib + * mutex longer than necessary. + */ + + if (!bhs[0]) + goto b_eio; + + wait_on_buffer(bhs[0]); + if (!buffer_uptodate(bhs[0])) { + *errp = -EIO; + goto b_eio; + } + + stream.workspace = zisofs_zlib_workspace; + mutex_lock(&zisofs_zlib_lock); + + zerr = zlib_inflateInit(&stream); + if (zerr != Z_OK) { + if (zerr == Z_MEM_ERROR) + *errp = -ENOMEM; + else + *errp = -EIO; + printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n", + zerr); + goto z_eio; + } + + while (curpage < pcount && curbh < haveblocks && + zerr != Z_STREAM_END) { + if (!stream.avail_out) { + if (pages[curpage]) { + stream.next_out = page_address(pages[curpage]) + + poffset; + stream.avail_out = PAGE_SIZE - poffset; + poffset = 0; + } else { + stream.next_out = (void *)&zisofs_sink_page; + stream.avail_out = PAGE_SIZE; + } + } + if (!stream.avail_in) { + wait_on_buffer(bhs[curbh]); + if (!buffer_uptodate(bhs[curbh])) { + *errp = -EIO; + break; + } + stream.next_in = bhs[curbh]->b_data + + (block_start & bufmask); + stream.avail_in = min_t(unsigned, bufsize - + (block_start & bufmask), + block_size); + block_size -= stream.avail_in; + block_start = 0; + } + + while (stream.avail_out && stream.avail_in) { + zerr = zlib_inflate(&stream, Z_SYNC_FLUSH); + if (zerr == Z_BUF_ERROR && stream.avail_in == 0) + break; + if (zerr == Z_STREAM_END) + break; + if (zerr != Z_OK) { + /* EOF, error, or trying to read beyond end of input */ + if (zerr == Z_MEM_ERROR) + *errp = -ENOMEM; + else { + printk(KERN_DEBUG + "zisofs: zisofs_inflate returned" + " %d, inode = %lu," + " page idx = %d, bh idx = %d," + " avail_in = %ld," + " avail_out = %ld\n", + zerr, inode->i_ino, curpage, + curbh, stream.avail_in, + stream.avail_out); + *errp = -EIO; + } + goto inflate_out; + } + } + + if (!stream.avail_out) { + /* This page completed */ + if (pages[curpage]) { + flush_dcache_page(pages[curpage]); + SetPageUptodate(pages[curpage]); + } + curpage++; + } + if (!stream.avail_in) + curbh++; + } +inflate_out: + zlib_inflateEnd(&stream); + +z_eio: + mutex_unlock(&zisofs_zlib_lock); + +b_eio: + for (i = 0; i < haveblocks; i++) + brelse(bhs[i]); + kfree(bhs); + return stream.total_out; +} + +/* + * Uncompress data so that pages[full_page] is fully uptodate and possibly + * fills in other pages if we have data for them. + */ +static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount, + struct page **pages) +{ + loff_t start_off, end_off; + loff_t block_start, block_end; + unsigned int header_size = ISOFS_I(inode)->i_format_parm[0]; + unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1]; + unsigned int blockptr; + loff_t poffset = 0; + blkcnt_t cstart_block, cend_block; + struct buffer_head *bh; + unsigned int blkbits = ISOFS_BUFFER_BITS(inode); + unsigned int blksize = 1 << blkbits; + int err; + loff_t ret; + + BUG_ON(!pages[full_page]); + + /* + * We want to read at least 'full_page' page. Because we have to + * uncompress the whole compression block anyway, fill the surrounding + * pages with the data we have anyway... + */ + start_off = page_offset(pages[full_page]); + end_off = min_t(loff_t, start_off + PAGE_SIZE, inode->i_size); + + cstart_block = start_off >> zisofs_block_shift; + cend_block = (end_off + (1 << zisofs_block_shift) - 1) + >> zisofs_block_shift; + + WARN_ON(start_off - (full_page << PAGE_SHIFT) != + ((cstart_block << zisofs_block_shift) & PAGE_MASK)); + + /* Find the pointer to this specific chunk */ + /* Note: we're not using isonum_731() here because the data is known aligned */ + /* Note: header_size is in 32-bit words (4 bytes) */ + blockptr = (header_size + cstart_block) << 2; + bh = isofs_bread(inode, blockptr >> blkbits); + if (!bh) + return -EIO; + block_start = le32_to_cpu(*(__le32 *) + (bh->b_data + (blockptr & (blksize - 1)))); + + while (cstart_block < cend_block && pcount > 0) { + /* Load end of the compressed block in the file */ + blockptr += 4; + /* Traversed to next block? */ + if (!(blockptr & (blksize - 1))) { + brelse(bh); + + bh = isofs_bread(inode, blockptr >> blkbits); + if (!bh) + return -EIO; + } + block_end = le32_to_cpu(*(__le32 *) + (bh->b_data + (blockptr & (blksize - 1)))); + if (block_start > block_end) { + brelse(bh); + return -EIO; + } + err = 0; + ret = zisofs_uncompress_block(inode, block_start, block_end, + pcount, pages, poffset, &err); + poffset += ret; + pages += poffset >> PAGE_SHIFT; + pcount -= poffset >> PAGE_SHIFT; + full_page -= poffset >> PAGE_SHIFT; + poffset &= ~PAGE_MASK; + + if (err) { + brelse(bh); + /* + * Did we finish reading the page we really wanted + * to read? + */ + if (full_page < 0) + return 0; + return err; + } + + block_start = block_end; + cstart_block++; + } + + if (poffset && *pages) { + memset(page_address(*pages) + poffset, 0, + PAGE_SIZE - poffset); + flush_dcache_page(*pages); + SetPageUptodate(*pages); + } + return 0; +} + +/* + * When decompressing, we typically obtain more than one page + * per reference. We inject the additional pages into the page + * cache as a form of readahead. + */ +static int zisofs_readpage(struct file *file, struct page *page) +{ + struct inode *inode = file_inode(file); + struct address_space *mapping = inode->i_mapping; + int err; + int i, pcount, full_page; + unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1]; + unsigned int zisofs_pages_per_cblock = + PAGE_SHIFT <= zisofs_block_shift ? + (1 << (zisofs_block_shift - PAGE_SHIFT)) : 0; + struct page **pages; + pgoff_t index = page->index, end_index; + + end_index = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; + /* + * If this page is wholly outside i_size we just return zero; + * do_generic_file_read() will handle this for us + */ + if (index >= end_index) { + SetPageUptodate(page); + unlock_page(page); + return 0; + } + + if (PAGE_SHIFT <= zisofs_block_shift) { + /* We have already been given one page, this is the one + we must do. */ + full_page = index & (zisofs_pages_per_cblock - 1); + pcount = min_t(int, zisofs_pages_per_cblock, + end_index - (index & ~(zisofs_pages_per_cblock - 1))); + index -= full_page; + } else { + full_page = 0; + pcount = 1; + } + pages = kcalloc(max_t(unsigned int, zisofs_pages_per_cblock, 1), + sizeof(*pages), GFP_KERNEL); + if (!pages) { + unlock_page(page); + return -ENOMEM; + } + pages[full_page] = page; + + for (i = 0; i < pcount; i++, index++) { + if (i != full_page) + pages[i] = grab_cache_page_nowait(mapping, index); + if (pages[i]) { + ClearPageError(pages[i]); + kmap(pages[i]); + } + } + + err = zisofs_fill_pages(inode, full_page, pcount, pages); + + /* Release any residual pages, do not SetPageUptodate */ + for (i = 0; i < pcount; i++) { + if (pages[i]) { + flush_dcache_page(pages[i]); + if (i == full_page && err) + SetPageError(pages[i]); + kunmap(pages[i]); + unlock_page(pages[i]); + if (i != full_page) + put_page(pages[i]); + } + } + + /* At this point, err contains 0 or -EIO depending on the "critical" page */ + kfree(pages); + return err; +} + +const struct address_space_operations zisofs_aops = { + .readpage = zisofs_readpage, + /* No bmap operation supported */ +}; + +int __init zisofs_init(void) +{ + zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize()); + if ( !zisofs_zlib_workspace ) + return -ENOMEM; + + return 0; +} + +void zisofs_cleanup(void) +{ + vfree(zisofs_zlib_workspace); +} |