1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* -*- linux-c -*- ------------------------------------------------------- *
3 *
4 * Copyright 2001 H. Peter Anvin - All Rights Reserved
5 *
6 * ----------------------------------------------------------------------- */
7
8 /*
9 * linux/fs/isofs/compress.c
10 *
11 * Transparent decompression of files on an iso9660 filesystem
12 */
13
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/bio.h>
17
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/zlib.h>
21
22 #include "isofs.h"
23 #include "zisofs.h"
24
25 /* This should probably be global. */
26 static char zisofs_sink_page[PAGE_SIZE];
27
28 /*
29 * This contains the zlib memory allocation and the mutex for the
30 * allocation; this avoids failures at block-decompression time.
31 */
32 static void *zisofs_zlib_workspace;
33 static DEFINE_MUTEX(zisofs_zlib_lock);
34
35 /*
36 * Read data of @inode from @block_start to @block_end and uncompress
37 * to one zisofs block. Store the data in the @pages array with @pcount
38 * entries. Start storing at offset @poffset of the first page.
39 */
zisofs_uncompress_block(struct inode * inode,loff_t block_start,loff_t block_end,int pcount,struct page ** pages,unsigned poffset,int * errp)40 static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start,
41 loff_t block_end, int pcount,
42 struct page **pages, unsigned poffset,
43 int *errp)
44 {
45 unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
46 unsigned int bufsize = ISOFS_BUFFER_SIZE(inode);
47 unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
48 unsigned int bufmask = bufsize - 1;
49 int i, block_size = block_end - block_start;
50 z_stream stream = { .total_out = 0,
51 .avail_in = 0,
52 .avail_out = 0, };
53 int zerr;
54 int needblocks = (block_size + (block_start & bufmask) + bufmask)
55 >> bufshift;
56 int haveblocks;
57 blkcnt_t blocknum;
58 struct buffer_head **bhs;
59 int curbh, curpage;
60
61 if (block_size > deflateBound(1UL << zisofs_block_shift)) {
62 *errp = -EIO;
63 return 0;
64 }
65 /* Empty block? */
66 if (block_size == 0) {
67 for ( i = 0 ; i < pcount ; i++ ) {
68 if (!pages[i])
69 continue;
70 memset(page_address(pages[i]), 0, PAGE_SIZE);
71 flush_dcache_page(pages[i]);
72 SetPageUptodate(pages[i]);
73 }
74 return ((loff_t)pcount) << PAGE_SHIFT;
75 }
76
77 /* Because zlib is not thread-safe, do all the I/O at the top. */
78 blocknum = block_start >> bufshift;
79 bhs = kcalloc(needblocks + 1, sizeof(*bhs), GFP_KERNEL);
80 if (!bhs) {
81 *errp = -ENOMEM;
82 return 0;
83 }
84 haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks);
85 ll_rw_block(REQ_OP_READ, 0, haveblocks, bhs);
86
87 curbh = 0;
88 curpage = 0;
89 /*
90 * First block is special since it may be fractional. We also wait for
91 * it before grabbing the zlib mutex; odds are that the subsequent
92 * blocks are going to come in in short order so we don't hold the zlib
93 * mutex longer than necessary.
94 */
95
96 if (!bhs[0])
97 goto b_eio;
98
99 wait_on_buffer(bhs[0]);
100 if (!buffer_uptodate(bhs[0])) {
101 *errp = -EIO;
102 goto b_eio;
103 }
104
105 stream.workspace = zisofs_zlib_workspace;
106 mutex_lock(&zisofs_zlib_lock);
107
108 zerr = zlib_inflateInit(&stream);
109 if (zerr != Z_OK) {
110 if (zerr == Z_MEM_ERROR)
111 *errp = -ENOMEM;
112 else
113 *errp = -EIO;
114 printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
115 zerr);
116 goto z_eio;
117 }
118
119 while (curpage < pcount && curbh < haveblocks &&
120 zerr != Z_STREAM_END) {
121 if (!stream.avail_out) {
122 if (pages[curpage]) {
123 stream.next_out = page_address(pages[curpage])
124 + poffset;
125 stream.avail_out = PAGE_SIZE - poffset;
126 poffset = 0;
127 } else {
128 stream.next_out = (void *)&zisofs_sink_page;
129 stream.avail_out = PAGE_SIZE;
130 }
131 }
132 if (!stream.avail_in) {
133 wait_on_buffer(bhs[curbh]);
134 if (!buffer_uptodate(bhs[curbh])) {
135 *errp = -EIO;
136 break;
137 }
138 stream.next_in = bhs[curbh]->b_data +
139 (block_start & bufmask);
140 stream.avail_in = min_t(unsigned, bufsize -
141 (block_start & bufmask),
142 block_size);
143 block_size -= stream.avail_in;
144 block_start = 0;
145 }
146
147 while (stream.avail_out && stream.avail_in) {
148 zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
149 if (zerr == Z_BUF_ERROR && stream.avail_in == 0)
150 break;
151 if (zerr == Z_STREAM_END)
152 break;
153 if (zerr != Z_OK) {
154 /* EOF, error, or trying to read beyond end of input */
155 if (zerr == Z_MEM_ERROR)
156 *errp = -ENOMEM;
157 else {
158 printk(KERN_DEBUG
159 "zisofs: zisofs_inflate returned"
160 " %d, inode = %lu,"
161 " page idx = %d, bh idx = %d,"
162 " avail_in = %ld,"
163 " avail_out = %ld\n",
164 zerr, inode->i_ino, curpage,
165 curbh, stream.avail_in,
166 stream.avail_out);
167 *errp = -EIO;
168 }
169 goto inflate_out;
170 }
171 }
172
173 if (!stream.avail_out) {
174 /* This page completed */
175 if (pages[curpage]) {
176 flush_dcache_page(pages[curpage]);
177 SetPageUptodate(pages[curpage]);
178 }
179 curpage++;
180 }
181 if (!stream.avail_in)
182 curbh++;
183 }
184 inflate_out:
185 zlib_inflateEnd(&stream);
186
187 z_eio:
188 mutex_unlock(&zisofs_zlib_lock);
189
190 b_eio:
191 for (i = 0; i < haveblocks; i++)
192 brelse(bhs[i]);
193 kfree(bhs);
194 return stream.total_out;
195 }
196
197 /*
198 * Uncompress data so that pages[full_page] is fully uptodate and possibly
199 * fills in other pages if we have data for them.
200 */
zisofs_fill_pages(struct inode * inode,int full_page,int pcount,struct page ** pages)201 static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount,
202 struct page **pages)
203 {
204 loff_t start_off, end_off;
205 loff_t block_start, block_end;
206 unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
207 unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
208 unsigned int blockptr;
209 loff_t poffset = 0;
210 blkcnt_t cstart_block, cend_block;
211 struct buffer_head *bh;
212 unsigned int blkbits = ISOFS_BUFFER_BITS(inode);
213 unsigned int blksize = 1 << blkbits;
214 int err;
215 loff_t ret;
216
217 BUG_ON(!pages[full_page]);
218
219 /*
220 * We want to read at least 'full_page' page. Because we have to
221 * uncompress the whole compression block anyway, fill the surrounding
222 * pages with the data we have anyway...
223 */
224 start_off = page_offset(pages[full_page]);
225 end_off = min_t(loff_t, start_off + PAGE_SIZE, inode->i_size);
226
227 cstart_block = start_off >> zisofs_block_shift;
228 cend_block = (end_off + (1 << zisofs_block_shift) - 1)
229 >> zisofs_block_shift;
230
231 WARN_ON(start_off - (full_page << PAGE_SHIFT) !=
232 ((cstart_block << zisofs_block_shift) & PAGE_MASK));
233
234 /* Find the pointer to this specific chunk */
235 /* Note: we're not using isonum_731() here because the data is known aligned */
236 /* Note: header_size is in 32-bit words (4 bytes) */
237 blockptr = (header_size + cstart_block) << 2;
238 bh = isofs_bread(inode, blockptr >> blkbits);
239 if (!bh)
240 return -EIO;
241 block_start = le32_to_cpu(*(__le32 *)
242 (bh->b_data + (blockptr & (blksize - 1))));
243
244 while (cstart_block < cend_block && pcount > 0) {
245 /* Load end of the compressed block in the file */
246 blockptr += 4;
247 /* Traversed to next block? */
248 if (!(blockptr & (blksize - 1))) {
249 brelse(bh);
250
251 bh = isofs_bread(inode, blockptr >> blkbits);
252 if (!bh)
253 return -EIO;
254 }
255 block_end = le32_to_cpu(*(__le32 *)
256 (bh->b_data + (blockptr & (blksize - 1))));
257 if (block_start > block_end) {
258 brelse(bh);
259 return -EIO;
260 }
261 err = 0;
262 ret = zisofs_uncompress_block(inode, block_start, block_end,
263 pcount, pages, poffset, &err);
264 poffset += ret;
265 pages += poffset >> PAGE_SHIFT;
266 pcount -= poffset >> PAGE_SHIFT;
267 full_page -= poffset >> PAGE_SHIFT;
268 poffset &= ~PAGE_MASK;
269
270 if (err) {
271 brelse(bh);
272 /*
273 * Did we finish reading the page we really wanted
274 * to read?
275 */
276 if (full_page < 0)
277 return 0;
278 return err;
279 }
280
281 block_start = block_end;
282 cstart_block++;
283 }
284
285 if (poffset && *pages) {
286 memset(page_address(*pages) + poffset, 0,
287 PAGE_SIZE - poffset);
288 flush_dcache_page(*pages);
289 SetPageUptodate(*pages);
290 }
291 return 0;
292 }
293
294 /*
295 * When decompressing, we typically obtain more than one page
296 * per reference. We inject the additional pages into the page
297 * cache as a form of readahead.
298 */
zisofs_readpage(struct file * file,struct page * page)299 static int zisofs_readpage(struct file *file, struct page *page)
300 {
301 struct inode *inode = file_inode(file);
302 struct address_space *mapping = inode->i_mapping;
303 int err;
304 int i, pcount, full_page;
305 unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
306 unsigned int zisofs_pages_per_cblock =
307 PAGE_SHIFT <= zisofs_block_shift ?
308 (1 << (zisofs_block_shift - PAGE_SHIFT)) : 0;
309 struct page **pages;
310 pgoff_t index = page->index, end_index;
311
312 end_index = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
313 /*
314 * If this page is wholly outside i_size we just return zero;
315 * do_generic_file_read() will handle this for us
316 */
317 if (index >= end_index) {
318 SetPageUptodate(page);
319 unlock_page(page);
320 return 0;
321 }
322
323 if (PAGE_SHIFT <= zisofs_block_shift) {
324 /* We have already been given one page, this is the one
325 we must do. */
326 full_page = index & (zisofs_pages_per_cblock - 1);
327 pcount = min_t(int, zisofs_pages_per_cblock,
328 end_index - (index & ~(zisofs_pages_per_cblock - 1)));
329 index -= full_page;
330 } else {
331 full_page = 0;
332 pcount = 1;
333 }
334 pages = kcalloc(max_t(unsigned int, zisofs_pages_per_cblock, 1),
335 sizeof(*pages), GFP_KERNEL);
336 if (!pages) {
337 unlock_page(page);
338 return -ENOMEM;
339 }
340 pages[full_page] = page;
341
342 for (i = 0; i < pcount; i++, index++) {
343 if (i != full_page)
344 pages[i] = grab_cache_page_nowait(mapping, index);
345 if (pages[i]) {
346 ClearPageError(pages[i]);
347 kmap(pages[i]);
348 }
349 }
350
351 err = zisofs_fill_pages(inode, full_page, pcount, pages);
352
353 /* Release any residual pages, do not SetPageUptodate */
354 for (i = 0; i < pcount; i++) {
355 if (pages[i]) {
356 flush_dcache_page(pages[i]);
357 if (i == full_page && err)
358 SetPageError(pages[i]);
359 kunmap(pages[i]);
360 unlock_page(pages[i]);
361 if (i != full_page)
362 put_page(pages[i]);
363 }
364 }
365
366 /* At this point, err contains 0 or -EIO depending on the "critical" page */
367 kfree(pages);
368 return err;
369 }
370
371 const struct address_space_operations zisofs_aops = {
372 .readpage = zisofs_readpage,
373 /* No bmap operation supported */
374 };
375
zisofs_init(void)376 int __init zisofs_init(void)
377 {
378 zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
379 if ( !zisofs_zlib_workspace )
380 return -ENOMEM;
381
382 return 0;
383 }
384
zisofs_cleanup(void)385 void zisofs_cleanup(void)
386 {
387 vfree(zisofs_zlib_workspace);
388 }
389