treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 142
[sfrench/cifs-2.6.git] / fs / isofs / compress.c
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  */
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  */
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  */
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
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
385 void zisofs_cleanup(void)
386 {
387         vfree(zisofs_zlib_workspace);
388 }