zisofs: fix readpage() outside i_size
[sfrench/cifs-2.6.git] / fs / isofs / compress.c
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
19 #include <linux/module.h>
20 #include <linux/init.h>
21
22 #include <linux/vmalloc.h>
23 #include <linux/zlib.h>
24
25 #include "isofs.h"
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;
36 static DEFINE_MUTEX(zisofs_zlib_lock);
37
38 /*
39  * When decompressing, we typically obtain more than one page
40  * per reference.  We inject the additional pages into the page
41  * cache as a form of readahead.
42  */
43 static int zisofs_readpage(struct file *file, struct page *page)
44 {
45         struct inode *inode = file->f_path.dentry->d_inode;
46         struct address_space *mapping = inode->i_mapping;
47         unsigned int maxpage, xpage, fpage, blockindex;
48         unsigned long offset;
49         unsigned long blockptr, blockendptr, cstart, cend, csize;
50         struct buffer_head *bh, *ptrbh[2];
51         unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
52         unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
53         unsigned long bufmask  = bufsize - 1;
54         int err = -EIO;
55         int i;
56         unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
57         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
58         /* unsigned long zisofs_block_size = 1UL << zisofs_block_shift; */
59         unsigned int zisofs_block_page_shift = zisofs_block_shift-PAGE_CACHE_SHIFT;
60         unsigned long zisofs_block_pages = 1UL << zisofs_block_page_shift;
61         unsigned long zisofs_block_page_mask = zisofs_block_pages-1;
62         struct page *pages[zisofs_block_pages];
63         unsigned long index = page->index;
64         int indexblocks;
65
66         /* We have already been given one page, this is the one
67            we must do. */
68         xpage = index & zisofs_block_page_mask;
69         pages[xpage] = page;
70  
71         /* The remaining pages need to be allocated and inserted */
72         offset = index & ~zisofs_block_page_mask;
73         blockindex = offset >> zisofs_block_page_shift;
74         maxpage = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
75
76         /*
77          * If this page is wholly outside i_size we just return zero;
78          * do_generic_file_read() will handle this for us
79          */
80         if (page->index >= maxpage) {
81                 SetPageUptodate(page);
82                 unlock_page(page);
83                 return 0;
84         }
85
86         maxpage = min(zisofs_block_pages, maxpage-offset);
87
88         for ( i = 0 ; i < maxpage ; i++, offset++ ) {
89                 if ( i != xpage ) {
90                         pages[i] = grab_cache_page_nowait(mapping, offset);
91                 }
92                 page = pages[i];
93                 if ( page ) {
94                         ClearPageError(page);
95                         kmap(page);
96                 }
97         }
98
99         /* This is the last page filled, plus one; used in case of abort. */
100         fpage = 0;
101
102         /* Find the pointer to this specific chunk */
103         /* Note: we're not using isonum_731() here because the data is known aligned */
104         /* Note: header_size is in 32-bit words (4 bytes) */
105         blockptr = (header_size + blockindex) << 2;
106         blockendptr = blockptr + 4;
107
108         indexblocks = ((blockptr^blockendptr) >> bufshift) ? 2 : 1;
109         ptrbh[0] = ptrbh[1] = NULL;
110
111         if ( isofs_get_blocks(inode, blockptr >> bufshift, ptrbh, indexblocks) != indexblocks ) {
112                 if ( ptrbh[0] ) brelse(ptrbh[0]);
113                 printk(KERN_DEBUG "zisofs: Null buffer on reading block table, inode = %lu, block = %lu\n",
114                        inode->i_ino, blockptr >> bufshift);
115                 goto eio;
116         }
117         ll_rw_block(READ, indexblocks, ptrbh);
118
119         bh = ptrbh[0];
120         if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
121                 printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
122                        inode->i_ino, blockptr >> bufshift);
123                 if ( ptrbh[1] )
124                         brelse(ptrbh[1]);
125                 goto eio;
126         }
127         cstart = le32_to_cpu(*(__le32 *)(bh->b_data + (blockptr & bufmask)));
128
129         if ( indexblocks == 2 ) {
130                 /* We just crossed a block boundary.  Switch to the next block */
131                 brelse(bh);
132                 bh = ptrbh[1];
133                 if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
134                         printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
135                                inode->i_ino, blockendptr >> bufshift);
136                         goto eio;
137                 }
138         }
139         cend = le32_to_cpu(*(__le32 *)(bh->b_data + (blockendptr & bufmask)));
140         brelse(bh);
141
142         if (cstart > cend)
143                 goto eio;
144                 
145         csize = cend-cstart;
146
147         if (csize > deflateBound(1UL << zisofs_block_shift))
148                 goto eio;
149
150         /* Now page[] contains an array of pages, any of which can be NULL,
151            and the locks on which we hold.  We should now read the data and
152            release the pages.  If the pages are NULL the decompressed data
153            for that particular page should be discarded. */
154         
155         if ( csize == 0 ) {
156                 /* This data block is empty. */
157
158                 for ( fpage = 0 ; fpage < maxpage ; fpage++ ) {
159                         if ( (page = pages[fpage]) != NULL ) {
160                                 memset(page_address(page), 0, PAGE_CACHE_SIZE);
161                                 
162                                 flush_dcache_page(page);
163                                 SetPageUptodate(page);
164                                 kunmap(page);
165                                 unlock_page(page);
166                                 if ( fpage == xpage )
167                                         err = 0; /* The critical page */
168                                 else
169                                         page_cache_release(page);
170                         }
171                 }
172         } else {
173                 /* This data block is compressed. */
174                 z_stream stream;
175                 int bail = 0, left_out = -1;
176                 int zerr;
177                 int needblocks = (csize + (cstart & bufmask) + bufmask) >> bufshift;
178                 int haveblocks;
179                 struct buffer_head *bhs[needblocks+1];
180                 struct buffer_head **bhptr;
181
182                 /* Because zlib is not thread-safe, do all the I/O at the top. */
183
184                 blockptr = cstart >> bufshift;
185                 memset(bhs, 0, (needblocks+1)*sizeof(struct buffer_head *));
186                 haveblocks = isofs_get_blocks(inode, blockptr, bhs, needblocks);
187                 ll_rw_block(READ, haveblocks, bhs);
188
189                 bhptr = &bhs[0];
190                 bh = *bhptr++;
191
192                 /* First block is special since it may be fractional.
193                    We also wait for it before grabbing the zlib
194                    mutex; odds are that the subsequent blocks are
195                    going to come in in short order so we don't hold
196                    the zlib mutex longer than necessary. */
197
198                 if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
199                         printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
200                                fpage, xpage, csize);
201                         goto b_eio;
202                 }
203                 stream.next_in  = bh->b_data + (cstart & bufmask);
204                 stream.avail_in = min(bufsize-(cstart & bufmask), csize);
205                 csize -= stream.avail_in;
206
207                 stream.workspace = zisofs_zlib_workspace;
208                 mutex_lock(&zisofs_zlib_lock);
209                 
210                 zerr = zlib_inflateInit(&stream);
211                 if ( zerr != Z_OK ) {
212                         if ( err && zerr == Z_MEM_ERROR )
213                                 err = -ENOMEM;
214                         printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
215                                zerr);
216                         goto z_eio;
217                 }
218
219                 while ( !bail && fpage < maxpage ) {
220                         page = pages[fpage];
221                         if ( page )
222                                 stream.next_out = page_address(page);
223                         else
224                                 stream.next_out = (void *)&zisofs_sink_page;
225                         stream.avail_out = PAGE_CACHE_SIZE;
226
227                         while ( stream.avail_out ) {
228                                 int ao, ai;
229                                 if ( stream.avail_in == 0 && left_out ) {
230                                         if ( !csize ) {
231                                                 printk(KERN_WARNING "zisofs: ZF read beyond end of input\n");
232                                                 bail = 1;
233                                                 break;
234                                         } else {
235                                                 bh = *bhptr++;
236                                                 if ( !bh ||
237                                                      (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
238                                                         /* Reached an EIO */
239                                                         printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
240                                                                fpage, xpage, csize);
241                                                                
242                                                         bail = 1;
243                                                         break;
244                                                 }
245                                                 stream.next_in = bh->b_data;
246                                                 stream.avail_in = min(csize,bufsize);
247                                                 csize -= stream.avail_in;
248                                         }
249                                 }
250                                 ao = stream.avail_out;  ai = stream.avail_in;
251                                 zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
252                                 left_out = stream.avail_out;
253                                 if ( zerr == Z_BUF_ERROR && stream.avail_in == 0 )
254                                         continue;
255                                 if ( zerr != Z_OK ) {
256                                         /* EOF, error, or trying to read beyond end of input */
257                                         if ( err && zerr == Z_MEM_ERROR )
258                                                 err = -ENOMEM;
259                                         if ( zerr != Z_STREAM_END )
260                                                 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",
261                                                        zerr, inode->i_ino, index,
262                                                        fpage, xpage,
263                                                        stream.avail_in, stream.avail_out,
264                                                        ai, ao);
265                                         bail = 1;
266                                         break;
267                                 }
268                         }
269
270                         if ( stream.avail_out && zerr == Z_STREAM_END ) {
271                                 /* Fractional page written before EOF.  This may
272                                    be the last page in the file. */
273                                 memset(stream.next_out, 0, stream.avail_out);
274                                 stream.avail_out = 0;
275                         }
276
277                         if ( !stream.avail_out ) {
278                                 /* This page completed */
279                                 if ( page ) {
280                                         flush_dcache_page(page);
281                                         SetPageUptodate(page);
282                                         kunmap(page);
283                                         unlock_page(page);
284                                         if ( fpage == xpage )
285                                                 err = 0; /* The critical page */
286                                         else
287                                                 page_cache_release(page);
288                                 }
289                                 fpage++;
290                         }
291                 }
292                 zlib_inflateEnd(&stream);
293
294         z_eio:
295                 mutex_unlock(&zisofs_zlib_lock);
296
297         b_eio:
298                 for ( i = 0 ; i < haveblocks ; i++ ) {
299                         if ( bhs[i] )
300                                 brelse(bhs[i]);
301                 }
302         }
303
304 eio:
305
306         /* Release any residual pages, do not SetPageUptodate */
307         while ( fpage < maxpage ) {
308                 page = pages[fpage];
309                 if ( page ) {
310                         flush_dcache_page(page);
311                         if ( fpage == xpage )
312                                 SetPageError(page);
313                         kunmap(page);
314                         unlock_page(page);
315                         if ( fpage != xpage )
316                                 page_cache_release(page);
317                 }
318                 fpage++;
319         }                       
320
321         /* At this point, err contains 0 or -EIO depending on the "critical" page */
322         return err;
323 }
324
325 const struct address_space_operations zisofs_aops = {
326         .readpage = zisofs_readpage,
327         /* No sync_page operation supported? */
328         /* No bmap operation supported */
329 };
330
331 int __init zisofs_init(void)
332 {
333         zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
334         if ( !zisofs_zlib_workspace )
335                 return -ENOMEM;
336
337         return 0;
338 }
339
340 void zisofs_cleanup(void)
341 {
342         vfree(zisofs_zlib_workspace);
343 }