fs/isofs/compress.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* -*- linux-c -*- ------------------------------------------------------- *
  *
  *   Copyright 2001 H. Peter Anvin - All Rights Reserved
  *
  * ----------------------------------------------------------------------- */

 /*
  * 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, 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_read_folio(struct file *file, struct folio *folio)
 {
 	struct page *page = &folio->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 = {
 	.read_folio = zisofs_read_folio,
 	/* 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);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* -- linux-c -- ------------------------------------------------------- *
	*
	* Copyright 2001 H. Peter Anvin - All Rights Reserved
	*
	* ----------------------------------------------------------------------- */

	/*
	* 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, 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_read_folio(struct file file, struct folio folio)
	{
	struct page *page = &folio->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 = {
	.read_folio = zisofs_read_folio,
	/* 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);
	}