1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Squashfs - a compressed read only filesystem for Linux
4 *
5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
6 * Phillip Lougher <phillip@squashfs.org.uk>
7 *
8 * block.c
9 */
10
11 /*
12 * This file implements the low-level routines to read and decompress
13 * datablocks and metadata blocks.
14 */
15
16 #include <linux/blkdev.h>
17 #include <linux/fs.h>
18 #include <linux/vfs.h>
19 #include <linux/slab.h>
20 #include <linux/pagemap.h>
21 #include <linux/string.h>
22 #include <linux/buffer_head.h>
23 #include <linux/bio.h>
24
25 #include "squashfs_fs.h"
26 #include "squashfs_fs_sb.h"
27 #include "squashfs.h"
28 #include "decompressor.h"
29 #include "page_actor.h"
30
31 /*
32 * Returns the amount of bytes copied to the page actor.
33 */
copy_bio_to_actor(struct bio * bio,struct squashfs_page_actor * actor,int offset,int req_length)34 static int copy_bio_to_actor(struct bio *bio,
35 struct squashfs_page_actor *actor,
36 int offset, int req_length)
37 {
38 void *actor_addr;
39 struct bvec_iter_all iter_all = {};
40 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
41 int copied_bytes = 0;
42 int actor_offset = 0;
43
44 squashfs_actor_nobuff(actor);
45 actor_addr = squashfs_first_page(actor);
46
47 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
48 return 0;
49
50 while (copied_bytes < req_length) {
51 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
52 PAGE_SIZE - actor_offset);
53
54 bytes_to_copy = min_t(int, bytes_to_copy,
55 req_length - copied_bytes);
56 if (!IS_ERR(actor_addr))
57 memcpy(actor_addr + actor_offset, bvec_virt(bvec) +
58 offset, bytes_to_copy);
59
60 actor_offset += bytes_to_copy;
61 copied_bytes += bytes_to_copy;
62 offset += bytes_to_copy;
63
64 if (actor_offset >= PAGE_SIZE) {
65 actor_addr = squashfs_next_page(actor);
66 if (!actor_addr)
67 break;
68 actor_offset = 0;
69 }
70 if (offset >= bvec->bv_len) {
71 if (!bio_next_segment(bio, &iter_all))
72 break;
73 offset = 0;
74 }
75 }
76 squashfs_finish_page(actor);
77 return copied_bytes;
78 }
79
squashfs_bio_read_cached(struct bio * fullbio,struct address_space * cache_mapping,u64 index,int length,u64 read_start,u64 read_end,int page_count)80 static int squashfs_bio_read_cached(struct bio *fullbio,
81 struct address_space *cache_mapping, u64 index, int length,
82 u64 read_start, u64 read_end, int page_count)
83 {
84 struct page *head_to_cache = NULL, *tail_to_cache = NULL;
85 int start_idx = 0, end_idx = 0;
86 struct bvec_iter_all iter_all;
87 struct bio *bio = NULL;
88 struct bio_vec *bv;
89 int idx = 0;
90 int err = 0;
91
92 bio_for_each_segment_all(bv, fullbio, iter_all) {
93 struct page *page = bv->bv_page;
94
95 if (page->mapping == cache_mapping) {
96 idx++;
97 continue;
98 }
99
100 /*
101 * We only use this when the device block size is the same as
102 * the page size, so read_start and read_end cover full pages.
103 *
104 * Compare these to the original required index and length to
105 * only cache pages which were requested partially, since these
106 * are the ones which are likely to be needed when reading
107 * adjacent blocks.
108 */
109 if (idx == 0 && index != read_start)
110 head_to_cache = page;
111 else if (idx == page_count - 1 && index + length != read_end)
112 tail_to_cache = page;
113
114 if (!bio || idx != end_idx) {
115 struct bio *new = bio_clone_fast(fullbio,
116 GFP_NOIO, &fs_bio_set);
117
118 if (bio) {
119 bio_trim(bio, start_idx * PAGE_SECTORS,
120 (end_idx - start_idx) * PAGE_SECTORS);
121 bio_chain(bio, new);
122 submit_bio(bio);
123 }
124
125 bio = new;
126 start_idx = idx;
127 }
128
129 idx++;
130 end_idx = idx;
131 }
132
133 if (bio) {
134 bio_trim(bio, start_idx * PAGE_SECTORS,
135 (end_idx - start_idx) * PAGE_SECTORS);
136 err = submit_bio_wait(bio);
137 bio_put(bio);
138 }
139
140 if (err)
141 return err;
142
143 if (head_to_cache) {
144 int ret = add_to_page_cache_lru(head_to_cache, cache_mapping,
145 read_start >> PAGE_SHIFT,
146 GFP_NOIO);
147
148 if (!ret) {
149 SetPageUptodate(head_to_cache);
150 unlock_page(head_to_cache);
151 }
152
153 }
154
155 if (tail_to_cache) {
156 int ret = add_to_page_cache_lru(tail_to_cache, cache_mapping,
157 (read_end >> PAGE_SHIFT) - 1,
158 GFP_NOIO);
159
160 if (!ret) {
161 SetPageUptodate(tail_to_cache);
162 unlock_page(tail_to_cache);
163 }
164 }
165
166 return 0;
167 }
168
squashfs_get_cache_page(struct address_space * mapping,pgoff_t index)169 static struct page *squashfs_get_cache_page(struct address_space *mapping,
170 pgoff_t index)
171 {
172 struct page *page;
173
174 if (!mapping)
175 return NULL;
176
177 page = find_get_page(mapping, index);
178 if (!page)
179 return NULL;
180
181 if (!PageUptodate(page)) {
182 put_page(page);
183 return NULL;
184 }
185
186 return page;
187 }
188
squashfs_bio_read(struct super_block * sb,u64 index,int length,struct bio ** biop,int * block_offset)189 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
190 struct bio **biop, int *block_offset)
191 {
192 struct squashfs_sb_info *msblk = sb->s_fs_info;
193 struct address_space *cache_mapping = msblk->cache_mapping;
194 const u64 read_start = round_down(index, msblk->devblksize);
195 const sector_t block = read_start >> msblk->devblksize_log2;
196 const u64 read_end = round_up(index + length, msblk->devblksize);
197 const sector_t block_end = read_end >> msblk->devblksize_log2;
198 int offset = read_start - round_down(index, PAGE_SIZE);
199 int total_len = (block_end - block) << msblk->devblksize_log2;
200 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
201 int error, i;
202 struct bio *bio;
203
204 if (page_count <= BIO_MAX_VECS)
205 bio = bio_alloc(GFP_NOIO, page_count);
206 else
207 bio = bio_kmalloc(GFP_NOIO, page_count);
208
209 if (!bio)
210 return -ENOMEM;
211
212 bio_set_dev(bio, sb->s_bdev);
213 bio->bi_opf = READ;
214 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
215
216 for (i = 0; i < page_count; ++i) {
217 unsigned int len =
218 min_t(unsigned int, PAGE_SIZE - offset, total_len);
219 pgoff_t index = (read_start >> PAGE_SHIFT) + i;
220 struct page *page;
221
222 page = squashfs_get_cache_page(cache_mapping, index);
223 if (!page)
224 page = alloc_page(GFP_NOIO);
225
226 if (!page) {
227 error = -ENOMEM;
228 goto out_free_bio;
229 }
230
231 /*
232 * Use the __ version to avoid merging since we need each page
233 * to be separate when we check for and avoid cached pages.
234 */
235 __bio_add_page(bio, page, len, offset);
236 offset = 0;
237 total_len -= len;
238 }
239
240 if (cache_mapping)
241 error = squashfs_bio_read_cached(bio, cache_mapping, index,
242 length, read_start, read_end,
243 page_count);
244 else
245 error = submit_bio_wait(bio);
246 if (error)
247 goto out_free_bio;
248
249 *biop = bio;
250 *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
251 return 0;
252
253 out_free_bio:
254 bio_free_pages(bio);
255 bio_put(bio);
256 return error;
257 }
258
259 /*
260 * Read and decompress a metadata block or datablock. Length is non-zero
261 * if a datablock is being read (the size is stored elsewhere in the
262 * filesystem), otherwise the length is obtained from the first two bytes of
263 * the metadata block. A bit in the length field indicates if the block
264 * is stored uncompressed in the filesystem (usually because compression
265 * generated a larger block - this does occasionally happen with compression
266 * algorithms).
267 */
squashfs_read_data(struct super_block * sb,u64 index,int length,u64 * next_index,struct squashfs_page_actor * output)268 int squashfs_read_data(struct super_block *sb, u64 index, int length,
269 u64 *next_index, struct squashfs_page_actor *output)
270 {
271 struct squashfs_sb_info *msblk = sb->s_fs_info;
272 struct bio *bio = NULL;
273 int compressed;
274 int res;
275 int offset;
276
277 if (length) {
278 /*
279 * Datablock.
280 */
281 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
282 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
283 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
284 index, compressed ? "" : "un", length, output->length);
285 } else {
286 /*
287 * Metadata block.
288 */
289 const u8 *data;
290 struct bvec_iter_all iter_all = {};
291 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
292
293 if (index + 2 > msblk->bytes_used) {
294 res = -EIO;
295 goto out;
296 }
297 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
298 if (res)
299 goto out;
300
301 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
302 res = -EIO;
303 goto out_free_bio;
304 }
305 /* Extract the length of the metadata block */
306 data = bvec_virt(bvec);
307 length = data[offset];
308 if (offset < bvec->bv_len - 1) {
309 length |= data[offset + 1] << 8;
310 } else {
311 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
312 res = -EIO;
313 goto out_free_bio;
314 }
315 data = bvec_virt(bvec);
316 length |= data[0] << 8;
317 }
318 bio_free_pages(bio);
319 bio_put(bio);
320
321 compressed = SQUASHFS_COMPRESSED(length);
322 length = SQUASHFS_COMPRESSED_SIZE(length);
323 index += 2;
324
325 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
326 compressed ? "" : "un", length);
327 }
328 if (length < 0 || length > output->length ||
329 (index + length) > msblk->bytes_used) {
330 res = -EIO;
331 goto out;
332 }
333
334 if (next_index)
335 *next_index = index + length;
336
337 res = squashfs_bio_read(sb, index, length, &bio, &offset);
338 if (res)
339 goto out;
340
341 if (compressed) {
342 if (!msblk->stream) {
343 res = -EIO;
344 goto out_free_bio;
345 }
346 res = squashfs_decompress(msblk, bio, offset, length, output);
347 } else {
348 res = copy_bio_to_actor(bio, output, offset, length);
349 }
350
351 out_free_bio:
352 bio_free_pages(bio);
353 bio_put(bio);
354 out:
355 if (res < 0) {
356 ERROR("Failed to read block 0x%llx: %d\n", index, res);
357 if (msblk->panic_on_errors)
358 panic("squashfs read failed");
359 }
360
361 return res;
362 }
363