- 根目录:
- fs
- isofs
- compress.c
/* -*- 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/vmalloc.h>
#include <linux/zlib.h>
#include "isofs.h"
#include "zisofs.h"
/* This should probably be global. */
static char zisofs_sink_page[PAGE_CACHE_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[needblocks + 1];
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_CACHE_SIZE);
flush_dcache_page(pages[i]);
SetPageUptodate(pages[i]);
}
return ((loff_t)pcount) << PAGE_CACHE_SHIFT;
}
/* Because zlib is not thread-safe, do all the I/O at the top. */
blocknum = block_start >> bufshift;
memset(bhs, 0, (needblocks + 1) * sizeof(struct buffer_head *));
haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks);
ll_rw_block(READ, 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_CACHE_SIZE - poffset;
poffset = 0;
} else {
stream.next_out = (void *)&zisofs_sink_page;
stream.avail_out = PAGE_CACHE_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 = %d,"
" avail_out = %d\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]);
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_CACHE_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_CACHE_SHIFT) !=
((cstart_block << zisofs_block_shift) & PAGE_CACHE_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_CACHE_SHIFT;
pcount -= poffset >> PAGE_CACHE_SHIFT;
full_page -= poffset >> PAGE_CACHE_SHIFT;
poffset &= ~PAGE_CACHE_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_CACHE_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->f_path.dentry->d_inode;
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_CACHE_SHIFT <= zisofs_block_shift ?
(1 << (zisofs_block_shift - PAGE_CACHE_SHIFT)) : 0;
struct page *pages[max_t(unsigned, zisofs_pages_per_cblock, 1)];
pgoff_t index = page->index, end_index;
end_index = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_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_CACHE_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[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)
page_cache_release(pages[i]);
}
}
/* At this point, err contains 0 or -EIO depending on the "critical" page */
return err;
}
const struct address_space_operations zisofs_aops = {
.readpage = zisofs_readpage,
/* No sync_page operation supported? */
/* 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);
}