[net-next-2.6.git] / 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);
}
Commit	Line	Data
1da177e4 LT	1	/* -- linux-c -- ------------------------------------------------------- *
	2	*
	3	* Copyright 2001 H. Peter Anvin - All Rights Reserved
	4	*
	5	* This program is free software; you can redistribute it and/or modify
	6	* it under the terms of the GNU General Public License as published by
	7	* the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
	8	* USA; either version 2 of the License, or (at your option) any later
	9	* version; incorporated herein by reference.
	10	*
	11	* ----------------------------------------------------------------------- */
	12
	13	/*
	14	* linux/fs/isofs/compress.c
	15	*
	16	* Transparent decompression of files on an iso9660 filesystem
	17	*/
	18
1da177e4	19	#include <linux/module.h>
1da177e4	20	#include <linux/init.h>
94f2f715	21
1da177e4 LT	22	#include <linux/vmalloc.h>
1da177e4 LT	23	#include <linux/zlib.h>
1da177e4	24
94f2f715	25	#include "isofs.h"
1da177e4 LT	26	#include "zisofs.h"
	27
	28	/* This should probably be global. */
	29	static char zisofs_sink_page[PAGE_CACHE_SIZE];
	30
	31	/*
	32	* This contains the zlib memory allocation and the mutex for the
	33	* allocation; this avoids failures at block-decompression time.
	34	*/
	35	static void *zisofs_zlib_workspace;
a36a151e	36	static DEFINE_MUTEX(zisofs_zlib_lock);
1da177e4 LT	37
1da177e4 LT	38	/*
59bc0552 JK	39	* Read data of @inode from @block_start to @block_end and uncompress
	40	* to one zisofs block. Store the data in the @pages array with @pcount
	41	* entries. Start storing at offset @poffset of the first page.
1da177e4	42	*/
59bc0552 JK	43	static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start,
	44	loff_t block_end, int pcount,
	45	struct page **pages, unsigned poffset,
	46	int *errp)
1da177e4	47	{
1da177e4	48	unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
59bc0552 JK	49	unsigned int bufsize = ISOFS_BUFFER_SIZE(inode);
	50	unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
	51	unsigned int bufmask = bufsize - 1;
	52	int i, block_size = block_end - block_start;
	53	z_stream stream = { .total_out = 0,
	54	.avail_in = 0,
	55	.avail_out = 0, };
	56	int zerr;
	57	int needblocks = (block_size + (block_start & bufmask) + bufmask)
	58	>> bufshift;
	59	int haveblocks;
	60	blkcnt_t blocknum;
	61	struct buffer_head *bhs[needblocks + 1];
	62	int curbh, curpage;
	63
	64	if (block_size > deflateBound(1UL << zisofs_block_shift)) {
	65	*errp = -EIO;
08ca0db8 DY	66	return 0;
08ca0db8 DY	67	}
59bc0552 JK	68	/* Empty block? */
	69	if (block_size == 0) {
	70	for ( i = 0 ; i < pcount ; i++ ) {
	71	if (!pages[i])
	72	continue;
	73	memset(page_address(pages[i]), 0, PAGE_CACHE_SIZE);
	74	flush_dcache_page(pages[i]);
	75	SetPageUptodate(pages[i]);
1da177e4	76	}
59bc0552	77	return ((loff_t)pcount) << PAGE_CACHE_SHIFT;
1da177e4 LT	78	}
1da177e4 LT	79
59bc0552 JK	80	/* Because zlib is not thread-safe, do all the I/O at the top. */
	81	blocknum = block_start >> bufshift;
	82	memset(bhs, 0, (needblocks + 1) * sizeof(struct buffer_head *));
	83	haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks);
	84	ll_rw_block(READ, haveblocks, bhs);
1da177e4	85
59bc0552 JK	86	curbh = 0;
	87	curpage = 0;
	88	/*
	89	* First block is special since it may be fractional. We also wait for
	90	* it before grabbing the zlib mutex; odds are that the subsequent
	91	* blocks are going to come in in short order so we don't hold the zlib
	92	* mutex longer than necessary.
	93	*/
1da177e4	94
59bc0552 JK	95	if (!bhs[0])
59bc0552 JK	96	goto b_eio;
1da177e4	97
59bc0552 JK	98	wait_on_buffer(bhs[0]);
	99	if (!buffer_uptodate(bhs[0])) {
	100	*errp = -EIO;
	101	goto b_eio;
1da177e4	102	}
1da177e4	103
59bc0552 JK	104	stream.workspace = zisofs_zlib_workspace;
59bc0552 JK	105	mutex_lock(&zisofs_zlib_lock);
fab5a60a	106
59bc0552 JK	107	zerr = zlib_inflateInit(&stream);
	108	if (zerr != Z_OK) {
	109	if (zerr == Z_MEM_ERROR)
	110	*errp = -ENOMEM;
	111	else
	112	*errp = -EIO;
	113	printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
	114	zerr);
	115	goto z_eio;
	116	}
	117
	118	while (curpage < pcount && curbh < haveblocks &&
	119	zerr != Z_STREAM_END) {
	120	if (!stream.avail_out) {
	121	if (pages[curpage]) {
	122	stream.next_out = page_address(pages[curpage])
	123	+ poffset;
	124	stream.avail_out = PAGE_CACHE_SIZE - poffset;
	125	poffset = 0;
	126	} else {
	127	stream.next_out = (void *)&zisofs_sink_page;
	128	stream.avail_out = PAGE_CACHE_SIZE;
1da177e4 LT	129	}
1da177e4 LT	130	}
59bc0552 JK	131	if (!stream.avail_in) {
	132	wait_on_buffer(bhs[curbh]);
	133	if (!buffer_uptodate(bhs[curbh])) {
	134	*errp = -EIO;
	135	break;
	136	}
	137	stream.next_in = bhs[curbh]->b_data +
	138	(block_start & bufmask);
	139	stream.avail_in = min_t(unsigned, bufsize -
	140	(block_start & bufmask),
	141	block_size);
	142	block_size -= stream.avail_in;
	143	block_start = 0;
1da177e4 LT	144	}
1da177e4 LT	145
59bc0552 JK	146	while (stream.avail_out && stream.avail_in) {
	147	zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
	148	if (zerr == Z_BUF_ERROR && stream.avail_in == 0)
	149	break;
	150	if (zerr == Z_STREAM_END)
	151	break;
	152	if (zerr != Z_OK) {
	153	/* EOF, error, or trying to read beyond end of input */
	154	if (zerr == Z_MEM_ERROR)
	155	*errp = -ENOMEM;
	156	else {
	157	printk(KERN_DEBUG
	158	"zisofs: zisofs_inflate returned"
	159	" %d, inode = %lu,"
	160	" page idx = %d, bh idx = %d,"
	161	" avail_in = %d,"
	162	" avail_out = %d\n",
	163	zerr, inode->i_ino, curpage,
	164	curbh, stream.avail_in,
	165	stream.avail_out);
	166	*errp = -EIO;
1da177e4	167	}
59bc0552	168	goto inflate_out;
1da177e4	169	}
59bc0552	170	}
1da177e4	171
59bc0552 JK	172	if (!stream.avail_out) {
	173	/* This page completed */
	174	if (pages[curpage]) {
	175	flush_dcache_page(pages[curpage]);
	176	SetPageUptodate(pages[curpage]);
1da177e4	177	}
59bc0552 JK	178	curpage++;
	179	}
	180	if (!stream.avail_in)
	181	curbh++;
	182	}
	183	inflate_out:
	184	zlib_inflateEnd(&stream);
1da177e4	185
59bc0552 JK	186	z_eio:
	187	mutex_unlock(&zisofs_zlib_lock);
	188
	189	b_eio:
	190	for (i = 0; i < haveblocks; i++)
	191	brelse(bhs[i]);
	192	return stream.total_out;
	193	}
	194
	195	/*
	196	* Uncompress data so that pages[full_page] is fully uptodate and possibly
	197	* fills in other pages if we have data for them.
	198	*/
	199	static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount,
	200	struct page **pages)
	201	{
	202	loff_t start_off, end_off;
	203	loff_t block_start, block_end;
	204	unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
	205	unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
	206	unsigned int blockptr;
	207	loff_t poffset = 0;
	208	blkcnt_t cstart_block, cend_block;
	209	struct buffer_head *bh;
	210	unsigned int blkbits = ISOFS_BUFFER_BITS(inode);
	211	unsigned int blksize = 1 << blkbits;
	212	int err;
	213	loff_t ret;
	214
	215	BUG_ON(!pages[full_page]);
	216
	217	/*
	218	* We want to read at least 'full_page' page. Because we have to
	219	* uncompress the whole compression block anyway, fill the surrounding
	220	* pages with the data we have anyway...
	221	*/
	222	start_off = page_offset(pages[full_page]);
	223	end_off = min_t(loff_t, start_off + PAGE_CACHE_SIZE, inode->i_size);
	224
	225	cstart_block = start_off >> zisofs_block_shift;
	226	cend_block = (end_off + (1 << zisofs_block_shift) - 1)
	227	>> zisofs_block_shift;
	228
	229	WARN_ON(start_off - (full_page << PAGE_CACHE_SHIFT) !=
	230	((cstart_block << zisofs_block_shift) & PAGE_CACHE_MASK));
	231
	232	/* Find the pointer to this specific chunk */
	233	/* Note: we're not using isonum_731() here because the data is known aligned */
	234	/* Note: header_size is in 32-bit words (4 bytes) */
	235	blockptr = (header_size + cstart_block) << 2;
	236	bh = isofs_bread(inode, blockptr >> blkbits);
	237	if (!bh)
	238	return -EIO;
	239	block_start = le32_to_cpu((__le32 )
	240	(bh->b_data + (blockptr & (blksize - 1))));
	241
	242	while (cstart_block < cend_block && pcount > 0) {
	243	/* Load end of the compressed block in the file */
	244	blockptr += 4;
	245	/* Traversed to next block? */
	246	if (!(blockptr & (blksize - 1))) {
	247	brelse(bh);
	248
	249	bh = isofs_bread(inode, blockptr >> blkbits);
250	if (!bh)
251	return -EIO;
252	}
253	block_end = le32_to_cpu((__le32 )
254	(bh->b_data + (blockptr & (blksize - 1))));
255	if (block_start > block_end) {
256	brelse(bh);
257	return -EIO;
258	}
259	err = 0;
260	ret = zisofs_uncompress_block(inode, block_start, block_end,
261	pcount, pages, poffset, &err);
262	poffset += ret;
263	pages += poffset >> PAGE_CACHE_SHIFT;
264	pcount -= poffset >> PAGE_CACHE_SHIFT;
265	full_page -= poffset >> PAGE_CACHE_SHIFT;
266	poffset &= ~PAGE_CACHE_MASK;
267
268	if (err) {
269	brelse(bh);
270	/*
271	* Did we finish reading the page we really wanted
272	* to read?
273	*/
274	if (full_page < 0)
275	return 0;
276	return err;
1da177e4	277	}
1da177e4	278
59bc0552 JK	279	block_start = block_end;
	280	cstart_block++;
	281	}
	282
	283	if (poffset && *pages) {
	284	memset(page_address(*pages) + poffset, 0,
	285	PAGE_CACHE_SIZE - poffset);
	286	flush_dcache_page(*pages);
	287	SetPageUptodate(*pages);
	288	}
	289	return 0;
	290	}
1da177e4	291
59bc0552 JK	292	/*
	293	* When decompressing, we typically obtain more than one page
	294	* per reference. We inject the additional pages into the page
	295	* cache as a form of readahead.
	296	*/
	297	static int zisofs_readpage(struct file file, struct page page)
	298	{
	299	struct inode *inode = file->f_path.dentry->d_inode;
	300	struct address_space *mapping = inode->i_mapping;
	301	int err;
	302	int i, pcount, full_page;
	303	unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
	304	unsigned int zisofs_pages_per_cblock =
	305	PAGE_CACHE_SHIFT <= zisofs_block_shift ?
	306	(1 << (zisofs_block_shift - PAGE_CACHE_SHIFT)) : 0;
	307	struct page *pages[max_t(unsigned, zisofs_pages_per_cblock, 1)];
	308	pgoff_t index = page->index, end_index;
	309
	310	end_index = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	311	/*
	312	* If this page is wholly outside i_size we just return zero;
	313	* do_generic_file_read() will handle this for us
	314	*/
	315	if (index >= end_index) {
	316	SetPageUptodate(page);
	317	unlock_page(page);
	318	return 0;
	319	}
	320
	321	if (PAGE_CACHE_SHIFT <= zisofs_block_shift) {
	322	/* We have already been given one page, this is the one
	323	we must do. */
	324	full_page = index & (zisofs_pages_per_cblock - 1);
	325	pcount = min_t(int, zisofs_pages_per_cblock,
	326	end_index - (index & ~(zisofs_pages_per_cblock - 1)));
	327	index -= full_page;
	328	} else {
	329	full_page = 0;
	330	pcount = 1;
	331	}
	332	pages[full_page] = page;
	333
	334	for (i = 0; i < pcount; i++, index++) {
	335	if (i != full_page)
	336	pages[i] = grab_cache_page_nowait(mapping, index);
	337	if (pages[i]) {
	338	ClearPageError(pages[i]);
	339	kmap(pages[i]);
1da177e4 LT	340	}
	341	}
	342
59bc0552	343	err = zisofs_fill_pages(inode, full_page, pcount, pages);
1da177e4 LT	344
1da177e4 LT	345	/* Release any residual pages, do not SetPageUptodate */
59bc0552 JK	346	for (i = 0; i < pcount; i++) {
	347	if (pages[i]) {
	348	flush_dcache_page(pages[i]);
	349	if (i == full_page && err)
	350	SetPageError(pages[i]);
	351	kunmap(pages[i]);
	352	unlock_page(pages[i]);
	353	if (i != full_page)
	354	page_cache_release(pages[i]);
1da177e4	355	}
1da177e4 LT	356	}
	357
	358	/* At this point, err contains 0 or -EIO depending on the "critical" page */
	359	return err;
	360	}
	361
f5e54d6e	362	const struct address_space_operations zisofs_aops = {
1da177e4 LT	363	.readpage = zisofs_readpage,
	364	/* No sync_page operation supported? */
	365	/* No bmap operation supported */
	366	};
	367
1da177e4 LT	368	int __init zisofs_init(void)
1da177e4 LT	369	{
1da177e4 LT	370	zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
	371	if ( !zisofs_zlib_workspace )
	372	return -ENOMEM;
1da177e4	373
1da177e4 LT	374	return 0;
	375	}
	376
	377	void zisofs_cleanup(void)
	378	{
1da177e4	379	vfree(zisofs_zlib_workspace);
1da177e4	380	}