aboutsummaryrefslogtreecommitdiffstats
path: root/fs/isofs/compress.c
blob: 34a44e451689afd59aa30449b56f938bd0109f60 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
/* -*- 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/config.h>
#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 struct semaphore zisofs_zlib_semaphore;

/*
 * 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_dentry->d_inode;
	struct address_space *mapping = inode->i_mapping;
	unsigned int maxpage, xpage, fpage, blockindex;
	unsigned long offset;
	unsigned long blockptr, blockendptr, cstart, cend, csize;
	struct buffer_head *bh, *ptrbh[2];
	unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
	unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
	unsigned long bufmask  = bufsize - 1;
	int err = -EIO;
	int i;
	unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
	unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
	/* unsigned long zisofs_block_size = 1UL << zisofs_block_shift; */
	unsigned int zisofs_block_page_shift = zisofs_block_shift-PAGE_CACHE_SHIFT;
	unsigned long zisofs_block_pages = 1UL << zisofs_block_page_shift;
	unsigned long zisofs_block_page_mask = zisofs_block_pages-1;
	struct page *pages[zisofs_block_pages];
	unsigned long index = page->index;
	int indexblocks;

	/* We have already been given one page, this is the one
	   we must do. */
	xpage = index & zisofs_block_page_mask;
	pages[xpage] = page;
 
	/* The remaining pages need to be allocated and inserted */
	offset = index & ~zisofs_block_page_mask;
	blockindex = offset >> zisofs_block_page_shift;
	maxpage = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	maxpage = min(zisofs_block_pages, maxpage-offset);

	for ( i = 0 ; i < maxpage ; i++, offset++ ) {
		if ( i != xpage ) {
			pages[i] = grab_cache_page_nowait(mapping, offset);
		}
		page = pages[i];
		if ( page ) {
			ClearPageError(page);
			kmap(page);
		}
	}

	/* This is the last page filled, plus one; used in case of abort. */
	fpage = 0;

	/* 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 + blockindex) << 2;
	blockendptr = blockptr + 4;

	indexblocks = ((blockptr^blockendptr) >> bufshift) ? 2 : 1;
	ptrbh[0] = ptrbh[1] = NULL;

	if ( isofs_get_blocks(inode, blockptr >> bufshift, ptrbh, indexblocks) != indexblocks ) {
		if ( ptrbh[0] ) brelse(ptrbh[0]);
		printk(KERN_DEBUG "zisofs: Null buffer on reading block table, inode = %lu, block = %lu\n",
		       inode->i_ino, blockptr >> bufshift);
		goto eio;
	}
	ll_rw_block(READ, indexblocks, ptrbh);

	bh = ptrbh[0];
	if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
		printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
		       inode->i_ino, blockptr >> bufshift);
		if ( ptrbh[1] )
			brelse(ptrbh[1]);
		goto eio;
	}
	cstart = le32_to_cpu(*(__le32 *)(bh->b_data + (blockptr & bufmask)));

	if ( indexblocks == 2 ) {
		/* We just crossed a block boundary.  Switch to the next block */
		brelse(bh);
		bh = ptrbh[1];
		if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
			printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
			       inode->i_ino, blockendptr >> bufshift);
			goto eio;
		}
	}
	cend = le32_to_cpu(*(__le32 *)(bh->b_data + (blockendptr & bufmask)));
	brelse(bh);

	csize = cend-cstart;

	/* Now page[] contains an array of pages, any of which can be NULL,
	   and the locks on which we hold.  We should now read the data and
	   release the pages.  If the pages are NULL the decompressed data
	   for that particular page should be discarded. */
	
	if ( csize == 0 ) {
		/* This data block is empty. */

		for ( fpage = 0 ; fpage < maxpage ; fpage++ ) {
			if ( (page = pages[fpage]) != NULL ) {
				memset(page_address(page), 0, PAGE_CACHE_SIZE);
				
				flush_dcache_page(page);
				SetPageUptodate(page);
				kunmap(page);
				unlock_page(page);
				if ( fpage == xpage )
					err = 0; /* The critical page */
				else
					page_cache_release(page);
			}
		}
	} else {
		/* This data block is compressed. */
		z_stream stream;
		int bail = 0, left_out = -1;
		int zerr;
		int needblocks = (csize + (cstart & bufmask) + bufmask) >> bufshift;
		int haveblocks;
		struct buffer_head *bhs[needblocks+1];
		struct buffer_head **bhptr;

		/* Because zlib is not thread-safe, do all the I/O at the top. */

		blockptr = cstart >> bufshift;
		memset(bhs, 0, (needblocks+1)*sizeof(struct buffer_head *));
		haveblocks = isofs_get_blocks(inode, blockptr, bhs, needblocks);
		ll_rw_block(READ, haveblocks, bhs);

		bhptr = &bhs[0];
		bh = *bhptr++;

		/* First block is special since it may be fractional.
		   We also wait for it before grabbing the zlib
		   semaphore; odds are that the subsequent blocks are
		   going to come in in short order so we don't hold
		   the zlib semaphore longer than necessary. */

		if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
			printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
			       fpage, xpage, csize);
			goto b_eio;
		}
		stream.next_in  = bh->b_data + (cstart & bufmask);
		stream.avail_in = min(bufsize-(cstart & bufmask), csize);
		csize -= stream.avail_in;

		stream.workspace = zisofs_zlib_workspace;
		down(&zisofs_zlib_semaphore);
		
		zerr = zlib_inflateInit(&stream);
		if ( zerr != Z_OK ) {
			if ( err && zerr == Z_MEM_ERROR )
				err = -ENOMEM;
			printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
			       zerr);
			goto z_eio;
		}

		while ( !bail && fpage < maxpage ) {
			page = pages[fpage];
			if ( page )
				stream.next_out = page_address(page);
			else
				stream.next_out = (void *)&zisofs_sink_page;
			stream.avail_out = PAGE_CACHE_SIZE;

			while ( stream.avail_out ) {
				int ao, ai;
				if ( stream.avail_in == 0 && left_out ) {
					if ( !csize ) {
						printk(KERN_WARNING "zisofs: ZF read beyond end of input\n");
						bail = 1;
						break;
					} else {
						bh = *bhptr++;
						if ( !bh ||
						     (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
							/* Reached an EIO */
 							printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
							       fpage, xpage, csize);
							       
							bail = 1;
							break;
						}
						stream.next_in = bh->b_data;
						stream.avail_in = min(csize,bufsize);
						csize -= stream.avail_in;
					}
				}
				ao = stream.avail_out;  ai = stream.avail_in;
				zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
				left_out = stream.avail_out;
				if ( zerr == Z_BUF_ERROR && stream.avail_in == 0 )
					continue;
				if ( zerr != Z_OK ) {
					/* EOF, error, or trying to read beyond end of input */
					if ( err && zerr == Z_MEM_ERROR )
						err = -ENOMEM;
					if ( zerr != Z_STREAM_END )
						printk(KERN_DEBUG "zisofs: zisofs_inflate returned %d, inode = %lu, index = %lu, fpage = %d, xpage = %d, avail_in = %d, avail_out = %d, ai = %d, ao = %d\n",
						       zerr, inode->i_ino, index,
						       fpage, xpage,
						       stream.avail_in, stream.avail_out,
						       ai, ao);
					bail = 1;
					break;
				}
			}

			if ( stream.avail_out && zerr == Z_STREAM_END ) {
				/* Fractional page written before EOF.  This may
				   be the last page in the file. */
				memset(stream.next_out, 0, stream.avail_out);
				stream.avail_out = 0;
			}

			if ( !stream.avail_out ) {
				/* This page completed */
				if ( page ) {
					flush_dcache_page(page);
					SetPageUptodate(page);
					kunmap(page);
					unlock_page(page);
					if ( fpage == xpage )
						err = 0; /* The critical page */
					else
						page_cache_release(page);
				}
				fpage++;
			}
		}
		zlib_inflateEnd(&stream);

	z_eio:
		up(&zisofs_zlib_semaphore);

	b_eio:
		for ( i = 0 ; i < haveblocks ; i++ ) {
			if ( bhs[i] )
				brelse(bhs[i]);
		}
	}

eio:

	/* Release any residual pages, do not SetPageUptodate */
	while ( fpage < maxpage ) {
		page = pages[fpage];
		if ( page ) {
			flush_dcache_page(page);
			if ( fpage == xpage )
				SetPageError(page);
			kunmap(page);
			unlock_page(page);
			if ( fpage != xpage )
				page_cache_release(page);
		}
		fpage++;
	}			

	/* At this point, err contains 0 or -EIO depending on the "critical" page */
	return err;
}

struct address_space_operations zisofs_aops = {
	.readpage = zisofs_readpage,
	/* No sync_page operation supported? */
	/* No bmap operation supported */
};

static int initialized;

int __init zisofs_init(void)
{
	if ( initialized ) {
		printk("zisofs_init: called more than once\n");
		return 0;
	}

	zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
	if ( !zisofs_zlib_workspace )
		return -ENOMEM;
	init_MUTEX(&zisofs_zlib_semaphore);

	initialized = 1;
	return 0;
}

void zisofs_cleanup(void)
{
	if ( !initialized ) {
		printk("zisofs_cleanup: called without initialization\n");
		return;
	}

	vfree(zisofs_zlib_workspace);
	initialized = 0;
}