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/bio.h> 23 24 #include "squashfs_fs.h" 25 #include "squashfs_fs_sb.h" 26 #include "squashfs.h" 27 #include "decompressor.h" 28 #include "page_actor.h" 29 30 /* 31 * Returns the amount of bytes copied to the page actor. 32 */ 33 static int copy_bio_to_actor(struct bio *bio, 34 struct squashfs_page_actor *actor, 35 int offset, int req_length) 36 { 37 void *actor_addr; 38 struct bvec_iter_all iter_all = {}; 39 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 40 int copied_bytes = 0; 41 int actor_offset = 0; 42 43 squashfs_actor_nobuff(actor); 44 actor_addr = squashfs_first_page(actor); 45 46 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) 47 return 0; 48 49 while (copied_bytes < req_length) { 50 int bytes_to_copy = min_t(int, bvec->bv_len - offset, 51 PAGE_SIZE - actor_offset); 52 53 bytes_to_copy = min_t(int, bytes_to_copy, 54 req_length - copied_bytes); 55 if (!IS_ERR(actor_addr)) 56 memcpy(actor_addr + actor_offset, bvec_virt(bvec) + 57 offset, bytes_to_copy); 58 59 actor_offset += bytes_to_copy; 60 copied_bytes += bytes_to_copy; 61 offset += bytes_to_copy; 62 63 if (actor_offset >= PAGE_SIZE) { 64 actor_addr = squashfs_next_page(actor); 65 if (!actor_addr) 66 break; 67 actor_offset = 0; 68 } 69 if (offset >= bvec->bv_len) { 70 if (!bio_next_segment(bio, &iter_all)) 71 break; 72 offset = 0; 73 } 74 } 75 squashfs_finish_page(actor); 76 return copied_bytes; 77 } 78 79 static int squashfs_bio_read_cached(struct bio *fullbio, 80 struct address_space *cache_mapping, u64 index, int length, 81 u64 read_start, u64 read_end, int page_count) 82 { 83 struct page *head_to_cache = NULL, *tail_to_cache = NULL; 84 struct block_device *bdev = fullbio->bi_bdev; 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 #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL 92 struct page **cache_pages = kmalloc_array(page_count, 93 sizeof(void *), GFP_KERNEL | __GFP_ZERO); 94 #endif 95 96 bio_for_each_segment_all(bv, fullbio, iter_all) { 97 struct page *page = bv->bv_page; 98 99 if (page->mapping == cache_mapping) { 100 idx++; 101 continue; 102 } 103 104 /* 105 * We only use this when the device block size is the same as 106 * the page size, so read_start and read_end cover full pages. 107 * 108 * Compare these to the original required index and length to 109 * only cache pages which were requested partially, since these 110 * are the ones which are likely to be needed when reading 111 * adjacent blocks. 112 */ 113 if (idx == 0 && index != read_start) 114 head_to_cache = page; 115 else if (idx == page_count - 1 && index + length != read_end) 116 tail_to_cache = page; 117 #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL 118 /* Cache all pages in the BIO for repeated reads */ 119 else if (cache_pages) 120 cache_pages[idx] = page; 121 #endif 122 123 if (!bio || idx != end_idx) { 124 struct bio *new = bio_alloc_clone(bdev, fullbio, 125 GFP_NOIO, &fs_bio_set); 126 127 if (bio) { 128 bio_trim(bio, start_idx * PAGE_SECTORS, 129 (end_idx - start_idx) * PAGE_SECTORS); 130 bio_chain(bio, new); 131 submit_bio(bio); 132 } 133 134 bio = new; 135 start_idx = idx; 136 } 137 138 idx++; 139 end_idx = idx; 140 } 141 142 if (bio) { 143 bio_trim(bio, start_idx * PAGE_SECTORS, 144 (end_idx - start_idx) * PAGE_SECTORS); 145 err = submit_bio_wait(bio); 146 bio_put(bio); 147 } 148 149 if (err) 150 return err; 151 152 if (head_to_cache) { 153 int ret = add_to_page_cache_lru(head_to_cache, cache_mapping, 154 read_start >> PAGE_SHIFT, 155 GFP_NOIO); 156 157 if (!ret) { 158 SetPageUptodate(head_to_cache); 159 unlock_page(head_to_cache); 160 } 161 162 } 163 164 if (tail_to_cache) { 165 int ret = add_to_page_cache_lru(tail_to_cache, cache_mapping, 166 (read_end >> PAGE_SHIFT) - 1, 167 GFP_NOIO); 168 169 if (!ret) { 170 SetPageUptodate(tail_to_cache); 171 unlock_page(tail_to_cache); 172 } 173 } 174 175 #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL 176 if (!cache_pages) 177 goto out; 178 179 for (idx = 0; idx < page_count; idx++) { 180 if (!cache_pages[idx]) 181 continue; 182 int ret = add_to_page_cache_lru(cache_pages[idx], cache_mapping, 183 (read_start >> PAGE_SHIFT) + idx, 184 GFP_NOIO); 185 186 if (!ret) { 187 SetPageUptodate(cache_pages[idx]); 188 unlock_page(cache_pages[idx]); 189 } 190 } 191 kfree(cache_pages); 192 out: 193 #endif 194 return 0; 195 } 196 197 static struct page *squashfs_get_cache_page(struct address_space *mapping, 198 pgoff_t index) 199 { 200 struct page *page; 201 202 if (!mapping) 203 return NULL; 204 205 page = find_get_page(mapping, index); 206 if (!page) 207 return NULL; 208 209 if (!PageUptodate(page)) { 210 put_page(page); 211 return NULL; 212 } 213 214 return page; 215 } 216 217 static int squashfs_bio_read(struct super_block *sb, u64 index, int length, 218 struct bio **biop, int *block_offset) 219 { 220 struct squashfs_sb_info *msblk = sb->s_fs_info; 221 struct address_space *cache_mapping = msblk->cache_mapping; 222 const u64 read_start = round_down(index, msblk->devblksize); 223 const sector_t block = read_start >> msblk->devblksize_log2; 224 const u64 read_end = round_up(index + length, msblk->devblksize); 225 const sector_t block_end = read_end >> msblk->devblksize_log2; 226 int offset = read_start - round_down(index, PAGE_SIZE); 227 int total_len = (block_end - block) << msblk->devblksize_log2; 228 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE); 229 int error, i; 230 struct bio *bio; 231 232 bio = bio_kmalloc(page_count, GFP_NOIO); 233 if (!bio) 234 return -ENOMEM; 235 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ); 236 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 237 238 for (i = 0; i < page_count; ++i) { 239 unsigned int len = 240 min_t(unsigned int, PAGE_SIZE - offset, total_len); 241 pgoff_t index = (read_start >> PAGE_SHIFT) + i; 242 struct page *page; 243 244 page = squashfs_get_cache_page(cache_mapping, index); 245 if (!page) 246 page = alloc_page(GFP_NOIO); 247 248 if (!page) { 249 error = -ENOMEM; 250 goto out_free_bio; 251 } 252 253 /* 254 * Use the __ version to avoid merging since we need each page 255 * to be separate when we check for and avoid cached pages. 256 */ 257 __bio_add_page(bio, page, len, offset); 258 offset = 0; 259 total_len -= len; 260 } 261 262 if (cache_mapping) 263 error = squashfs_bio_read_cached(bio, cache_mapping, index, 264 length, read_start, read_end, 265 page_count); 266 else 267 error = submit_bio_wait(bio); 268 if (error) 269 goto out_free_bio; 270 271 *biop = bio; 272 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 273 return 0; 274 275 out_free_bio: 276 bio_free_pages(bio); 277 bio_uninit(bio); 278 kfree(bio); 279 return error; 280 } 281 282 /* 283 * Read and decompress a metadata block or datablock. Length is non-zero 284 * if a datablock is being read (the size is stored elsewhere in the 285 * filesystem), otherwise the length is obtained from the first two bytes of 286 * the metadata block. A bit in the length field indicates if the block 287 * is stored uncompressed in the filesystem (usually because compression 288 * generated a larger block - this does occasionally happen with compression 289 * algorithms). 290 */ 291 int squashfs_read_data(struct super_block *sb, u64 index, int length, 292 u64 *next_index, struct squashfs_page_actor *output) 293 { 294 struct squashfs_sb_info *msblk = sb->s_fs_info; 295 struct bio *bio = NULL; 296 int compressed; 297 int res; 298 int offset; 299 300 if (length) { 301 /* 302 * Datablock. 303 */ 304 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 305 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 306 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 307 index, compressed ? "" : "un", length, output->length); 308 } else { 309 /* 310 * Metadata block. 311 */ 312 const u8 *data; 313 struct bvec_iter_all iter_all = {}; 314 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 315 316 if (index + 2 > msblk->bytes_used) { 317 res = -EIO; 318 goto out; 319 } 320 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 321 if (res) 322 goto out; 323 324 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 325 res = -EIO; 326 goto out_free_bio; 327 } 328 /* Extract the length of the metadata block */ 329 data = bvec_virt(bvec); 330 length = data[offset]; 331 if (offset < bvec->bv_len - 1) { 332 length |= data[offset + 1] << 8; 333 } else { 334 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 335 res = -EIO; 336 goto out_free_bio; 337 } 338 data = bvec_virt(bvec); 339 length |= data[0] << 8; 340 } 341 bio_free_pages(bio); 342 bio_uninit(bio); 343 kfree(bio); 344 345 compressed = SQUASHFS_COMPRESSED(length); 346 length = SQUASHFS_COMPRESSED_SIZE(length); 347 index += 2; 348 349 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2, 350 compressed ? "" : "un", length); 351 } 352 if (length <= 0 || length > output->length || 353 (index + length) > msblk->bytes_used) { 354 res = -EIO; 355 goto out; 356 } 357 358 if (next_index) 359 *next_index = index + length; 360 361 res = squashfs_bio_read(sb, index, length, &bio, &offset); 362 if (res) 363 goto out; 364 365 if (compressed) { 366 if (!msblk->stream) { 367 res = -EIO; 368 goto out_free_bio; 369 } 370 res = msblk->thread_ops->decompress(msblk, bio, offset, length, output); 371 } else { 372 res = copy_bio_to_actor(bio, output, offset, length); 373 } 374 375 out_free_bio: 376 bio_free_pages(bio); 377 bio_uninit(bio); 378 kfree(bio); 379 out: 380 if (res < 0) { 381 ERROR("Failed to read block 0x%llx: %d\n", index, res); 382 if (msblk->panic_on_errors) 383 panic("squashfs read failed"); 384 } 385 386 return res; 387 } 388