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1701aecb PL |
1 | /* |
2 | * Squashfs - a compressed read only filesystem for Linux | |
3 | * | |
4 | * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | |
5 | * Phillip Lougher <phillip@lougher.demon.co.uk> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or | |
8 | * modify it under the terms of the GNU General Public License | |
9 | * as published by the Free Software Foundation; either version 2, | |
10 | * or (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | * GNU General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License | |
18 | * along with this program; if not, write to the Free Software | |
19 | * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | |
20 | * | |
21 | * file.c | |
22 | */ | |
23 | ||
24 | /* | |
25 | * This file contains code for handling regular files. A regular file | |
26 | * consists of a sequence of contiguous compressed blocks, and/or a | |
27 | * compressed fragment block (tail-end packed block). The compressed size | |
28 | * of each datablock is stored in a block list contained within the | |
29 | * file inode (itself stored in one or more compressed metadata blocks). | |
30 | * | |
31 | * To speed up access to datablocks when reading 'large' files (256 Mbytes or | |
32 | * larger), the code implements an index cache that caches the mapping from | |
33 | * block index to datablock location on disk. | |
34 | * | |
35 | * The index cache allows Squashfs to handle large files (up to 1.75 TiB) while | |
36 | * retaining a simple and space-efficient block list on disk. The cache | |
37 | * is split into slots, caching up to eight 224 GiB files (128 KiB blocks). | |
38 | * Larger files use multiple slots, with 1.75 TiB files using all 8 slots. | |
39 | * The index cache is designed to be memory efficient, and by default uses | |
40 | * 16 KiB. | |
41 | */ | |
42 | ||
43 | #include <linux/fs.h> | |
44 | #include <linux/vfs.h> | |
45 | #include <linux/kernel.h> | |
46 | #include <linux/slab.h> | |
47 | #include <linux/string.h> | |
48 | #include <linux/pagemap.h> | |
49 | #include <linux/mutex.h> | |
50 | #include <linux/zlib.h> | |
51 | ||
52 | #include "squashfs_fs.h" | |
53 | #include "squashfs_fs_sb.h" | |
54 | #include "squashfs_fs_i.h" | |
55 | #include "squashfs.h" | |
56 | ||
57 | /* | |
58 | * Locate cache slot in range [offset, index] for specified inode. If | |
59 | * there's more than one return the slot closest to index. | |
60 | */ | |
61 | static struct meta_index *locate_meta_index(struct inode *inode, int offset, | |
62 | int index) | |
63 | { | |
64 | struct meta_index *meta = NULL; | |
65 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; | |
66 | int i; | |
67 | ||
68 | mutex_lock(&msblk->meta_index_mutex); | |
69 | ||
70 | TRACE("locate_meta_index: index %d, offset %d\n", index, offset); | |
71 | ||
72 | if (msblk->meta_index == NULL) | |
73 | goto not_allocated; | |
74 | ||
75 | for (i = 0; i < SQUASHFS_META_SLOTS; i++) { | |
76 | if (msblk->meta_index[i].inode_number == inode->i_ino && | |
77 | msblk->meta_index[i].offset >= offset && | |
78 | msblk->meta_index[i].offset <= index && | |
79 | msblk->meta_index[i].locked == 0) { | |
80 | TRACE("locate_meta_index: entry %d, offset %d\n", i, | |
81 | msblk->meta_index[i].offset); | |
82 | meta = &msblk->meta_index[i]; | |
83 | offset = meta->offset; | |
84 | } | |
85 | } | |
86 | ||
87 | if (meta) | |
88 | meta->locked = 1; | |
89 | ||
90 | not_allocated: | |
91 | mutex_unlock(&msblk->meta_index_mutex); | |
92 | ||
93 | return meta; | |
94 | } | |
95 | ||
96 | ||
97 | /* | |
98 | * Find and initialise an empty cache slot for index offset. | |
99 | */ | |
100 | static struct meta_index *empty_meta_index(struct inode *inode, int offset, | |
101 | int skip) | |
102 | { | |
103 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; | |
104 | struct meta_index *meta = NULL; | |
105 | int i; | |
106 | ||
107 | mutex_lock(&msblk->meta_index_mutex); | |
108 | ||
109 | TRACE("empty_meta_index: offset %d, skip %d\n", offset, skip); | |
110 | ||
111 | if (msblk->meta_index == NULL) { | |
112 | /* | |
113 | * First time cache index has been used, allocate and | |
114 | * initialise. The cache index could be allocated at | |
115 | * mount time but doing it here means it is allocated only | |
116 | * if a 'large' file is read. | |
117 | */ | |
118 | msblk->meta_index = kcalloc(SQUASHFS_META_SLOTS, | |
119 | sizeof(*(msblk->meta_index)), GFP_KERNEL); | |
120 | if (msblk->meta_index == NULL) { | |
121 | ERROR("Failed to allocate meta_index\n"); | |
122 | goto failed; | |
123 | } | |
124 | for (i = 0; i < SQUASHFS_META_SLOTS; i++) { | |
125 | msblk->meta_index[i].inode_number = 0; | |
126 | msblk->meta_index[i].locked = 0; | |
127 | } | |
128 | msblk->next_meta_index = 0; | |
129 | } | |
130 | ||
131 | for (i = SQUASHFS_META_SLOTS; i && | |
132 | msblk->meta_index[msblk->next_meta_index].locked; i--) | |
133 | msblk->next_meta_index = (msblk->next_meta_index + 1) % | |
134 | SQUASHFS_META_SLOTS; | |
135 | ||
136 | if (i == 0) { | |
137 | TRACE("empty_meta_index: failed!\n"); | |
138 | goto failed; | |
139 | } | |
140 | ||
141 | TRACE("empty_meta_index: returned meta entry %d, %p\n", | |
142 | msblk->next_meta_index, | |
143 | &msblk->meta_index[msblk->next_meta_index]); | |
144 | ||
145 | meta = &msblk->meta_index[msblk->next_meta_index]; | |
146 | msblk->next_meta_index = (msblk->next_meta_index + 1) % | |
147 | SQUASHFS_META_SLOTS; | |
148 | ||
149 | meta->inode_number = inode->i_ino; | |
150 | meta->offset = offset; | |
151 | meta->skip = skip; | |
152 | meta->entries = 0; | |
153 | meta->locked = 1; | |
154 | ||
155 | failed: | |
156 | mutex_unlock(&msblk->meta_index_mutex); | |
157 | return meta; | |
158 | } | |
159 | ||
160 | ||
161 | static void release_meta_index(struct inode *inode, struct meta_index *meta) | |
162 | { | |
163 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; | |
164 | mutex_lock(&msblk->meta_index_mutex); | |
165 | meta->locked = 0; | |
166 | mutex_unlock(&msblk->meta_index_mutex); | |
167 | } | |
168 | ||
169 | ||
170 | /* | |
171 | * Read the next n blocks from the block list, starting from | |
172 | * metadata block <start_block, offset>. | |
173 | */ | |
174 | static long long read_indexes(struct super_block *sb, int n, | |
175 | u64 *start_block, int *offset) | |
176 | { | |
177 | int err, i; | |
178 | long long block = 0; | |
179 | __le32 *blist = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL); | |
180 | ||
181 | if (blist == NULL) { | |
182 | ERROR("read_indexes: Failed to allocate block_list\n"); | |
183 | return -ENOMEM; | |
184 | } | |
185 | ||
186 | while (n) { | |
187 | int blocks = min_t(int, n, PAGE_CACHE_SIZE >> 2); | |
188 | ||
189 | err = squashfs_read_metadata(sb, blist, start_block, | |
190 | offset, blocks << 2); | |
191 | if (err < 0) { | |
192 | ERROR("read_indexes: reading block [%llx:%x]\n", | |
193 | *start_block, *offset); | |
194 | goto failure; | |
195 | } | |
196 | ||
197 | for (i = 0; i < blocks; i++) { | |
198 | int size = le32_to_cpu(blist[i]); | |
199 | block += SQUASHFS_COMPRESSED_SIZE_BLOCK(size); | |
200 | } | |
201 | n -= blocks; | |
202 | } | |
203 | ||
204 | kfree(blist); | |
205 | return block; | |
206 | ||
207 | failure: | |
208 | kfree(blist); | |
209 | return err; | |
210 | } | |
211 | ||
212 | ||
213 | /* | |
214 | * Each cache index slot has SQUASHFS_META_ENTRIES, each of which | |
215 | * can cache one index -> datablock/blocklist-block mapping. We wish | |
216 | * to distribute these over the length of the file, entry[0] maps index x, | |
217 | * entry[1] maps index x + skip, entry[2] maps index x + 2 * skip, and so on. | |
218 | * The larger the file, the greater the skip factor. The skip factor is | |
219 | * limited to the size of the metadata cache (SQUASHFS_CACHED_BLKS) to ensure | |
220 | * the number of metadata blocks that need to be read fits into the cache. | |
221 | * If the skip factor is limited in this way then the file will use multiple | |
222 | * slots. | |
223 | */ | |
224 | static inline int calculate_skip(int blocks) | |
225 | { | |
226 | int skip = blocks / ((SQUASHFS_META_ENTRIES + 1) | |
227 | * SQUASHFS_META_INDEXES); | |
228 | return min(SQUASHFS_CACHED_BLKS - 1, skip + 1); | |
229 | } | |
230 | ||
231 | ||
232 | /* | |
233 | * Search and grow the index cache for the specified inode, returning the | |
234 | * on-disk locations of the datablock and block list metadata block | |
235 | * <index_block, index_offset> for index (scaled to nearest cache index). | |
236 | */ | |
237 | static int fill_meta_index(struct inode *inode, int index, | |
238 | u64 *index_block, int *index_offset, u64 *data_block) | |
239 | { | |
240 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; | |
241 | int skip = calculate_skip(i_size_read(inode) >> msblk->block_log); | |
242 | int offset = 0; | |
243 | struct meta_index *meta; | |
244 | struct meta_entry *meta_entry; | |
245 | u64 cur_index_block = squashfs_i(inode)->block_list_start; | |
246 | int cur_offset = squashfs_i(inode)->offset; | |
247 | u64 cur_data_block = squashfs_i(inode)->start; | |
248 | int err, i; | |
249 | ||
250 | /* | |
251 | * Scale index to cache index (cache slot entry) | |
252 | */ | |
253 | index /= SQUASHFS_META_INDEXES * skip; | |
254 | ||
255 | while (offset < index) { | |
256 | meta = locate_meta_index(inode, offset + 1, index); | |
257 | ||
258 | if (meta == NULL) { | |
259 | meta = empty_meta_index(inode, offset + 1, skip); | |
260 | if (meta == NULL) | |
261 | goto all_done; | |
262 | } else { | |
263 | offset = index < meta->offset + meta->entries ? index : | |
264 | meta->offset + meta->entries - 1; | |
265 | meta_entry = &meta->meta_entry[offset - meta->offset]; | |
266 | cur_index_block = meta_entry->index_block + | |
267 | msblk->inode_table; | |
268 | cur_offset = meta_entry->offset; | |
269 | cur_data_block = meta_entry->data_block; | |
270 | TRACE("get_meta_index: offset %d, meta->offset %d, " | |
271 | "meta->entries %d\n", offset, meta->offset, | |
272 | meta->entries); | |
273 | TRACE("get_meta_index: index_block 0x%llx, offset 0x%x" | |
274 | " data_block 0x%llx\n", cur_index_block, | |
275 | cur_offset, cur_data_block); | |
276 | } | |
277 | ||
278 | /* | |
279 | * If necessary grow cache slot by reading block list. Cache | |
280 | * slot is extended up to index or to the end of the slot, in | |
281 | * which case further slots will be used. | |
282 | */ | |
283 | for (i = meta->offset + meta->entries; i <= index && | |
284 | i < meta->offset + SQUASHFS_META_ENTRIES; i++) { | |
285 | int blocks = skip * SQUASHFS_META_INDEXES; | |
286 | long long res = read_indexes(inode->i_sb, blocks, | |
287 | &cur_index_block, &cur_offset); | |
288 | ||
289 | if (res < 0) { | |
290 | if (meta->entries == 0) | |
291 | /* | |
292 | * Don't leave an empty slot on read | |
293 | * error allocated to this inode... | |
294 | */ | |
295 | meta->inode_number = 0; | |
296 | err = res; | |
297 | goto failed; | |
298 | } | |
299 | ||
300 | cur_data_block += res; | |
301 | meta_entry = &meta->meta_entry[i - meta->offset]; | |
302 | meta_entry->index_block = cur_index_block - | |
303 | msblk->inode_table; | |
304 | meta_entry->offset = cur_offset; | |
305 | meta_entry->data_block = cur_data_block; | |
306 | meta->entries++; | |
307 | offset++; | |
308 | } | |
309 | ||
310 | TRACE("get_meta_index: meta->offset %d, meta->entries %d\n", | |
311 | meta->offset, meta->entries); | |
312 | ||
313 | release_meta_index(inode, meta); | |
314 | } | |
315 | ||
316 | all_done: | |
317 | *index_block = cur_index_block; | |
318 | *index_offset = cur_offset; | |
319 | *data_block = cur_data_block; | |
320 | ||
321 | /* | |
322 | * Scale cache index (cache slot entry) to index | |
323 | */ | |
324 | return offset * SQUASHFS_META_INDEXES * skip; | |
325 | ||
326 | failed: | |
327 | release_meta_index(inode, meta); | |
328 | return err; | |
329 | } | |
330 | ||
331 | ||
332 | /* | |
333 | * Get the on-disk location and compressed size of the datablock | |
334 | * specified by index. Fill_meta_index() does most of the work. | |
335 | */ | |
336 | static int read_blocklist(struct inode *inode, int index, u64 *block) | |
337 | { | |
338 | u64 start; | |
339 | long long blks; | |
340 | int offset; | |
341 | __le32 size; | |
342 | int res = fill_meta_index(inode, index, &start, &offset, block); | |
343 | ||
344 | TRACE("read_blocklist: res %d, index %d, start 0x%llx, offset" | |
345 | " 0x%x, block 0x%llx\n", res, index, start, offset, | |
346 | *block); | |
347 | ||
348 | if (res < 0) | |
349 | return res; | |
350 | ||
351 | /* | |
352 | * res contains the index of the mapping returned by fill_meta_index(), | |
353 | * this will likely be less than the desired index (because the | |
354 | * meta_index cache works at a higher granularity). Read any | |
355 | * extra block indexes needed. | |
356 | */ | |
357 | if (res < index) { | |
358 | blks = read_indexes(inode->i_sb, index - res, &start, &offset); | |
359 | if (blks < 0) | |
360 | return (int) blks; | |
361 | *block += blks; | |
362 | } | |
363 | ||
364 | /* | |
365 | * Read length of block specified by index. | |
366 | */ | |
367 | res = squashfs_read_metadata(inode->i_sb, &size, &start, &offset, | |
368 | sizeof(size)); | |
369 | if (res < 0) | |
370 | return res; | |
371 | return le32_to_cpu(size); | |
372 | } | |
373 | ||
374 | ||
375 | static int squashfs_readpage(struct file *file, struct page *page) | |
376 | { | |
377 | struct inode *inode = page->mapping->host; | |
378 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; | |
379 | int bytes, i, offset = 0, sparse = 0; | |
380 | struct squashfs_cache_entry *buffer = NULL; | |
381 | void *pageaddr; | |
382 | ||
383 | int mask = (1 << (msblk->block_log - PAGE_CACHE_SHIFT)) - 1; | |
384 | int index = page->index >> (msblk->block_log - PAGE_CACHE_SHIFT); | |
385 | int start_index = page->index & ~mask; | |
386 | int end_index = start_index | mask; | |
387 | int file_end = i_size_read(inode) >> msblk->block_log; | |
388 | ||
389 | TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n", | |
390 | page->index, squashfs_i(inode)->start); | |
391 | ||
392 | if (page->index >= ((i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> | |
393 | PAGE_CACHE_SHIFT)) | |
394 | goto out; | |
395 | ||
396 | if (index < file_end || squashfs_i(inode)->fragment_block == | |
397 | SQUASHFS_INVALID_BLK) { | |
398 | /* | |
399 | * Reading a datablock from disk. Need to read block list | |
400 | * to get location and block size. | |
401 | */ | |
402 | u64 block = 0; | |
403 | int bsize = read_blocklist(inode, index, &block); | |
404 | if (bsize < 0) | |
405 | goto error_out; | |
406 | ||
407 | if (bsize == 0) { /* hole */ | |
408 | bytes = index == file_end ? | |
409 | (i_size_read(inode) & (msblk->block_size - 1)) : | |
410 | msblk->block_size; | |
411 | sparse = 1; | |
412 | } else { | |
413 | /* | |
414 | * Read and decompress datablock. | |
415 | */ | |
416 | buffer = squashfs_get_datablock(inode->i_sb, | |
417 | block, bsize); | |
418 | if (buffer->error) { | |
419 | ERROR("Unable to read page, block %llx, size %x" | |
420 | "\n", block, bsize); | |
421 | squashfs_cache_put(buffer); | |
422 | goto error_out; | |
423 | } | |
424 | bytes = buffer->length; | |
425 | } | |
426 | } else { | |
427 | /* | |
428 | * Datablock is stored inside a fragment (tail-end packed | |
429 | * block). | |
430 | */ | |
431 | buffer = squashfs_get_fragment(inode->i_sb, | |
432 | squashfs_i(inode)->fragment_block, | |
433 | squashfs_i(inode)->fragment_size); | |
434 | ||
435 | if (buffer->error) { | |
436 | ERROR("Unable to read page, block %llx, size %x\n", | |
437 | squashfs_i(inode)->fragment_block, | |
438 | squashfs_i(inode)->fragment_size); | |
439 | squashfs_cache_put(buffer); | |
440 | goto error_out; | |
441 | } | |
442 | bytes = i_size_read(inode) & (msblk->block_size - 1); | |
443 | offset = squashfs_i(inode)->fragment_offset; | |
444 | } | |
445 | ||
446 | /* | |
447 | * Loop copying datablock into pages. As the datablock likely covers | |
448 | * many PAGE_CACHE_SIZE pages (default block size is 128 KiB) explicitly | |
449 | * grab the pages from the page cache, except for the page that we've | |
450 | * been called to fill. | |
451 | */ | |
452 | for (i = start_index; i <= end_index && bytes > 0; i++, | |
453 | bytes -= PAGE_CACHE_SIZE, offset += PAGE_CACHE_SIZE) { | |
454 | struct page *push_page; | |
455 | int avail = sparse ? 0 : min_t(int, bytes, PAGE_CACHE_SIZE); | |
456 | ||
457 | TRACE("bytes %d, i %d, available_bytes %d\n", bytes, i, avail); | |
458 | ||
459 | push_page = (i == page->index) ? page : | |
460 | grab_cache_page_nowait(page->mapping, i); | |
461 | ||
462 | if (!push_page) | |
463 | continue; | |
464 | ||
465 | if (PageUptodate(push_page)) | |
466 | goto skip_page; | |
467 | ||
468 | pageaddr = kmap_atomic(push_page, KM_USER0); | |
469 | squashfs_copy_data(pageaddr, buffer, offset, avail); | |
470 | memset(pageaddr + avail, 0, PAGE_CACHE_SIZE - avail); | |
471 | kunmap_atomic(pageaddr, KM_USER0); | |
472 | flush_dcache_page(push_page); | |
473 | SetPageUptodate(push_page); | |
474 | skip_page: | |
475 | unlock_page(push_page); | |
476 | if (i != page->index) | |
477 | page_cache_release(push_page); | |
478 | } | |
479 | ||
480 | if (!sparse) | |
481 | squashfs_cache_put(buffer); | |
482 | ||
483 | return 0; | |
484 | ||
485 | error_out: | |
486 | SetPageError(page); | |
487 | out: | |
488 | pageaddr = kmap_atomic(page, KM_USER0); | |
489 | memset(pageaddr, 0, PAGE_CACHE_SIZE); | |
490 | kunmap_atomic(pageaddr, KM_USER0); | |
491 | flush_dcache_page(page); | |
492 | if (!PageError(page)) | |
493 | SetPageUptodate(page); | |
494 | unlock_page(page); | |
495 | ||
496 | return 0; | |
497 | } | |
498 | ||
499 | ||
500 | const struct address_space_operations squashfs_aops = { | |
501 | .readpage = squashfs_readpage | |
502 | }; |