389 lines
9.9 KiB
C
389 lines
9.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright 2001 H. Peter Anvin - All Rights Reserved
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*
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* ----------------------------------------------------------------------- */
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/*
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* linux/fs/isofs/compress.c
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*
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* Transparent decompression of files on an iso9660 filesystem
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/bio.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/zlib.h>
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#include "isofs.h"
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#include "zisofs.h"
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/* This should probably be global. */
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static char zisofs_sink_page[PAGE_SIZE];
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/*
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* This contains the zlib memory allocation and the mutex for the
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* allocation; this avoids failures at block-decompression time.
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*/
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static void *zisofs_zlib_workspace;
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static DEFINE_MUTEX(zisofs_zlib_lock);
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/*
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* Read data of @inode from @block_start to @block_end and uncompress
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* to one zisofs block. Store the data in the @pages array with @pcount
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* entries. Start storing at offset @poffset of the first page.
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*/
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static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start,
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loff_t block_end, int pcount,
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struct page **pages, unsigned poffset,
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int *errp)
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{
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unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
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unsigned int bufsize = ISOFS_BUFFER_SIZE(inode);
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unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
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unsigned int bufmask = bufsize - 1;
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int i, block_size = block_end - block_start;
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z_stream stream = { .total_out = 0,
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.avail_in = 0,
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.avail_out = 0, };
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int zerr;
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int needblocks = (block_size + (block_start & bufmask) + bufmask)
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>> bufshift;
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int haveblocks;
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blkcnt_t blocknum;
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struct buffer_head **bhs;
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int curbh, curpage;
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if (block_size > deflateBound(1UL << zisofs_block_shift)) {
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*errp = -EIO;
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return 0;
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}
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/* Empty block? */
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if (block_size == 0) {
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for ( i = 0 ; i < pcount ; i++ ) {
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if (!pages[i])
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continue;
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memset(page_address(pages[i]), 0, PAGE_SIZE);
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flush_dcache_page(pages[i]);
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SetPageUptodate(pages[i]);
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}
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return ((loff_t)pcount) << PAGE_SHIFT;
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}
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/* Because zlib is not thread-safe, do all the I/O at the top. */
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blocknum = block_start >> bufshift;
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bhs = kcalloc(needblocks + 1, sizeof(*bhs), GFP_KERNEL);
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if (!bhs) {
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*errp = -ENOMEM;
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return 0;
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}
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haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks);
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ll_rw_block(REQ_OP_READ, 0, haveblocks, bhs);
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curbh = 0;
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curpage = 0;
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/*
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* First block is special since it may be fractional. We also wait for
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* it before grabbing the zlib mutex; odds are that the subsequent
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* blocks are going to come in in short order so we don't hold the zlib
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* mutex longer than necessary.
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*/
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if (!bhs[0])
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goto b_eio;
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wait_on_buffer(bhs[0]);
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if (!buffer_uptodate(bhs[0])) {
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*errp = -EIO;
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goto b_eio;
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}
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stream.workspace = zisofs_zlib_workspace;
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mutex_lock(&zisofs_zlib_lock);
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zerr = zlib_inflateInit(&stream);
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if (zerr != Z_OK) {
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if (zerr == Z_MEM_ERROR)
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*errp = -ENOMEM;
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else
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*errp = -EIO;
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printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
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zerr);
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goto z_eio;
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}
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while (curpage < pcount && curbh < haveblocks &&
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zerr != Z_STREAM_END) {
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if (!stream.avail_out) {
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if (pages[curpage]) {
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stream.next_out = page_address(pages[curpage])
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+ poffset;
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stream.avail_out = PAGE_SIZE - poffset;
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poffset = 0;
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} else {
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stream.next_out = (void *)&zisofs_sink_page;
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stream.avail_out = PAGE_SIZE;
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}
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}
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if (!stream.avail_in) {
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wait_on_buffer(bhs[curbh]);
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if (!buffer_uptodate(bhs[curbh])) {
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*errp = -EIO;
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break;
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}
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stream.next_in = bhs[curbh]->b_data +
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(block_start & bufmask);
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stream.avail_in = min_t(unsigned, bufsize -
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(block_start & bufmask),
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block_size);
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block_size -= stream.avail_in;
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block_start = 0;
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}
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while (stream.avail_out && stream.avail_in) {
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zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
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if (zerr == Z_BUF_ERROR && stream.avail_in == 0)
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break;
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if (zerr == Z_STREAM_END)
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break;
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if (zerr != Z_OK) {
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/* EOF, error, or trying to read beyond end of input */
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if (zerr == Z_MEM_ERROR)
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*errp = -ENOMEM;
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else {
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printk(KERN_DEBUG
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"zisofs: zisofs_inflate returned"
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" %d, inode = %lu,"
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" page idx = %d, bh idx = %d,"
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" avail_in = %ld,"
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" avail_out = %ld\n",
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zerr, inode->i_ino, curpage,
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curbh, stream.avail_in,
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stream.avail_out);
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*errp = -EIO;
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}
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goto inflate_out;
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}
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}
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if (!stream.avail_out) {
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/* This page completed */
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if (pages[curpage]) {
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flush_dcache_page(pages[curpage]);
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SetPageUptodate(pages[curpage]);
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}
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curpage++;
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}
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if (!stream.avail_in)
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curbh++;
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}
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inflate_out:
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zlib_inflateEnd(&stream);
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z_eio:
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mutex_unlock(&zisofs_zlib_lock);
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b_eio:
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for (i = 0; i < haveblocks; i++)
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brelse(bhs[i]);
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kfree(bhs);
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return stream.total_out;
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}
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/*
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* Uncompress data so that pages[full_page] is fully uptodate and possibly
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* fills in other pages if we have data for them.
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*/
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static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount,
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struct page **pages)
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{
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loff_t start_off, end_off;
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loff_t block_start, block_end;
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unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
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unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
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unsigned int blockptr;
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loff_t poffset = 0;
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blkcnt_t cstart_block, cend_block;
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struct buffer_head *bh;
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unsigned int blkbits = ISOFS_BUFFER_BITS(inode);
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unsigned int blksize = 1 << blkbits;
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int err;
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loff_t ret;
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BUG_ON(!pages[full_page]);
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/*
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* We want to read at least 'full_page' page. Because we have to
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* uncompress the whole compression block anyway, fill the surrounding
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* pages with the data we have anyway...
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*/
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start_off = page_offset(pages[full_page]);
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end_off = min_t(loff_t, start_off + PAGE_SIZE, inode->i_size);
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cstart_block = start_off >> zisofs_block_shift;
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cend_block = (end_off + (1 << zisofs_block_shift) - 1)
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>> zisofs_block_shift;
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WARN_ON(start_off - (full_page << PAGE_SHIFT) !=
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((cstart_block << zisofs_block_shift) & PAGE_MASK));
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/* Find the pointer to this specific chunk */
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/* Note: we're not using isonum_731() here because the data is known aligned */
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/* Note: header_size is in 32-bit words (4 bytes) */
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blockptr = (header_size + cstart_block) << 2;
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bh = isofs_bread(inode, blockptr >> blkbits);
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if (!bh)
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return -EIO;
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block_start = le32_to_cpu(*(__le32 *)
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(bh->b_data + (blockptr & (blksize - 1))));
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while (cstart_block < cend_block && pcount > 0) {
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/* Load end of the compressed block in the file */
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blockptr += 4;
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/* Traversed to next block? */
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if (!(blockptr & (blksize - 1))) {
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brelse(bh);
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bh = isofs_bread(inode, blockptr >> blkbits);
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if (!bh)
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return -EIO;
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}
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block_end = le32_to_cpu(*(__le32 *)
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(bh->b_data + (blockptr & (blksize - 1))));
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if (block_start > block_end) {
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brelse(bh);
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return -EIO;
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}
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err = 0;
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ret = zisofs_uncompress_block(inode, block_start, block_end,
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pcount, pages, poffset, &err);
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poffset += ret;
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pages += poffset >> PAGE_SHIFT;
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pcount -= poffset >> PAGE_SHIFT;
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full_page -= poffset >> PAGE_SHIFT;
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poffset &= ~PAGE_MASK;
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if (err) {
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brelse(bh);
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/*
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* Did we finish reading the page we really wanted
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* to read?
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*/
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if (full_page < 0)
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return 0;
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return err;
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}
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block_start = block_end;
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cstart_block++;
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}
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if (poffset && *pages) {
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memset(page_address(*pages) + poffset, 0,
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PAGE_SIZE - poffset);
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flush_dcache_page(*pages);
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SetPageUptodate(*pages);
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}
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return 0;
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}
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/*
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* When decompressing, we typically obtain more than one page
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* per reference. We inject the additional pages into the page
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* cache as a form of readahead.
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*/
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static int zisofs_readpage(struct file *file, struct page *page)
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{
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struct inode *inode = file_inode(file);
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struct address_space *mapping = inode->i_mapping;
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int err;
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int i, pcount, full_page;
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unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
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unsigned int zisofs_pages_per_cblock =
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PAGE_SHIFT <= zisofs_block_shift ?
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(1 << (zisofs_block_shift - PAGE_SHIFT)) : 0;
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struct page **pages;
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pgoff_t index = page->index, end_index;
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end_index = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
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/*
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* If this page is wholly outside i_size we just return zero;
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* do_generic_file_read() will handle this for us
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*/
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if (index >= end_index) {
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SetPageUptodate(page);
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unlock_page(page);
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return 0;
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}
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if (PAGE_SHIFT <= zisofs_block_shift) {
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/* We have already been given one page, this is the one
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we must do. */
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full_page = index & (zisofs_pages_per_cblock - 1);
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pcount = min_t(int, zisofs_pages_per_cblock,
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end_index - (index & ~(zisofs_pages_per_cblock - 1)));
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index -= full_page;
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} else {
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full_page = 0;
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pcount = 1;
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}
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pages = kcalloc(max_t(unsigned int, zisofs_pages_per_cblock, 1),
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sizeof(*pages), GFP_KERNEL);
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if (!pages) {
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unlock_page(page);
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return -ENOMEM;
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}
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pages[full_page] = page;
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for (i = 0; i < pcount; i++, index++) {
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if (i != full_page)
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pages[i] = grab_cache_page_nowait(mapping, index);
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if (pages[i]) {
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ClearPageError(pages[i]);
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kmap(pages[i]);
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}
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}
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err = zisofs_fill_pages(inode, full_page, pcount, pages);
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/* Release any residual pages, do not SetPageUptodate */
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for (i = 0; i < pcount; i++) {
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if (pages[i]) {
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flush_dcache_page(pages[i]);
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if (i == full_page && err)
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SetPageError(pages[i]);
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kunmap(pages[i]);
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unlock_page(pages[i]);
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if (i != full_page)
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put_page(pages[i]);
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}
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}
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/* At this point, err contains 0 or -EIO depending on the "critical" page */
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kfree(pages);
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return err;
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}
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const struct address_space_operations zisofs_aops = {
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.readpage = zisofs_readpage,
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/* No bmap operation supported */
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};
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int __init zisofs_init(void)
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{
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zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
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if ( !zisofs_zlib_workspace )
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return -ENOMEM;
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return 0;
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}
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void zisofs_cleanup(void)
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{
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vfree(zisofs_zlib_workspace);
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}
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