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 folio *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 folio_iter fi; 87 struct bio *bio = NULL; 88 int idx = 0; 89 int err = 0; 90 #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL 91 struct folio **cache_folios = kmalloc_array(page_count, 92 sizeof(*cache_folios), GFP_KERNEL | __GFP_ZERO); 93 #endif 94 95 bio_for_each_folio_all(fi, fullbio) { 96 struct folio *folio = fi.folio; 97 98 if (folio->mapping == cache_mapping) { 99 idx++; 100 continue; 101 } 102 103 /* 104 * We only use this when the device block size is the same as 105 * the page size, so read_start and read_end cover full pages. 106 * 107 * Compare these to the original required index and length to 108 * only cache pages which were requested partially, since these 109 * are the ones which are likely to be needed when reading 110 * adjacent blocks. 111 */ 112 if (idx == 0 && index != read_start) 113 head_to_cache = folio; 114 else if (idx == page_count - 1 && index + length != read_end) 115 tail_to_cache = folio; 116 #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL 117 /* Cache all pages in the BIO for repeated reads */ 118 else if (cache_folios) 119 cache_folios[idx] = folio; 120 #endif 121 122 if (!bio || idx != end_idx) { 123 struct bio *new = bio_alloc_clone(bdev, fullbio, 124 GFP_NOIO, &fs_bio_set); 125 126 if (bio) { 127 bio_trim(bio, start_idx * PAGE_SECTORS, 128 (end_idx - start_idx) * PAGE_SECTORS); 129 bio_chain(bio, new); 130 submit_bio(bio); 131 } 132 133 bio = new; 134 start_idx = idx; 135 } 136 137 idx++; 138 end_idx = idx; 139 } 140 141 if (bio) { 142 bio_trim(bio, start_idx * PAGE_SECTORS, 143 (end_idx - start_idx) * PAGE_SECTORS); 144 err = submit_bio_wait(bio); 145 bio_put(bio); 146 } 147 148 if (err) 149 return err; 150 151 if (head_to_cache) { 152 int ret = filemap_add_folio(cache_mapping, head_to_cache, 153 read_start >> PAGE_SHIFT, 154 GFP_NOIO); 155 156 if (!ret) { 157 folio_mark_uptodate(head_to_cache); 158 folio_unlock(head_to_cache); 159 } 160 161 } 162 163 if (tail_to_cache) { 164 int ret = filemap_add_folio(cache_mapping, tail_to_cache, 165 (read_end >> PAGE_SHIFT) - 1, 166 GFP_NOIO); 167 168 if (!ret) { 169 folio_mark_uptodate(tail_to_cache); 170 folio_unlock(tail_to_cache); 171 } 172 } 173 174 #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL 175 if (!cache_folios) 176 goto out; 177 178 for (idx = 0; idx < page_count; idx++) { 179 if (!cache_folios[idx]) 180 continue; 181 int ret = filemap_add_folio(cache_mapping, cache_folios[idx], 182 (read_start >> PAGE_SHIFT) + idx, 183 GFP_NOIO); 184 185 if (!ret) { 186 folio_mark_uptodate(cache_folios[idx]); 187 folio_unlock(cache_folios[idx]); 188 } 189 } 190 kfree(cache_folios); 191 out: 192 #endif 193 return 0; 194 } 195 196 static struct page *squashfs_get_cache_page(struct address_space *mapping, 197 pgoff_t index) 198 { 199 struct page *page; 200 201 if (!mapping) 202 return NULL; 203 204 page = find_get_page(mapping, index); 205 if (!page) 206 return NULL; 207 208 if (!PageUptodate(page)) { 209 put_page(page); 210 return NULL; 211 } 212 213 return page; 214 } 215 216 static int squashfs_bio_read(struct super_block *sb, u64 index, int length, 217 struct bio **biop, int *block_offset) 218 { 219 struct squashfs_sb_info *msblk = sb->s_fs_info; 220 struct address_space *cache_mapping = msblk->cache_mapping; 221 const u64 read_start = round_down(index, msblk->devblksize); 222 const sector_t block = read_start >> msblk->devblksize_log2; 223 const u64 read_end = round_up(index + length, msblk->devblksize); 224 const sector_t block_end = read_end >> msblk->devblksize_log2; 225 int offset = read_start - round_down(index, PAGE_SIZE); 226 int total_len = (block_end - block) << msblk->devblksize_log2; 227 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE); 228 int error, i; 229 struct bio *bio; 230 231 bio = bio_kmalloc(page_count, GFP_NOIO); 232 if (!bio) 233 return -ENOMEM; 234 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ); 235 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 236 237 for (i = 0; i < page_count; ++i) { 238 unsigned int len = 239 min_t(unsigned int, PAGE_SIZE - offset, total_len); 240 pgoff_t index = (read_start >> PAGE_SHIFT) + i; 241 struct page *page; 242 243 page = squashfs_get_cache_page(cache_mapping, index); 244 if (!page) 245 page = alloc_page(GFP_NOIO); 246 247 if (!page) { 248 error = -ENOMEM; 249 goto out_free_bio; 250 } 251 252 /* 253 * Use the __ version to avoid merging since we need each page 254 * to be separate when we check for and avoid cached pages. 255 */ 256 __bio_add_page(bio, page, len, offset); 257 offset = 0; 258 total_len -= len; 259 } 260 261 if (cache_mapping) 262 error = squashfs_bio_read_cached(bio, cache_mapping, index, 263 length, read_start, read_end, 264 page_count); 265 else 266 error = submit_bio_wait(bio); 267 if (error) 268 goto out_free_bio; 269 270 *biop = bio; 271 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 272 return 0; 273 274 out_free_bio: 275 bio_free_pages(bio); 276 bio_uninit(bio); 277 kfree(bio); 278 return error; 279 } 280 281 /* 282 * Read and decompress a metadata block or datablock. Length is non-zero 283 * if a datablock is being read (the size is stored elsewhere in the 284 * filesystem), otherwise the length is obtained from the first two bytes of 285 * the metadata block. A bit in the length field indicates if the block 286 * is stored uncompressed in the filesystem (usually because compression 287 * generated a larger block - this does occasionally happen with compression 288 * algorithms). 289 */ 290 int squashfs_read_data(struct super_block *sb, u64 index, int length, 291 u64 *next_index, struct squashfs_page_actor *output) 292 { 293 struct squashfs_sb_info *msblk = sb->s_fs_info; 294 struct bio *bio = NULL; 295 int compressed; 296 int res; 297 int offset; 298 299 if (length) { 300 /* 301 * Datablock. 302 */ 303 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 304 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 305 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 306 index, compressed ? "" : "un", length, output->length); 307 } else { 308 /* 309 * Metadata block. 310 */ 311 const u8 *data; 312 struct bvec_iter_all iter_all = {}; 313 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 314 315 if (index + 2 > msblk->bytes_used) { 316 res = -EIO; 317 goto out; 318 } 319 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 320 if (res) 321 goto out; 322 323 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 324 res = -EIO; 325 goto out_free_bio; 326 } 327 /* Extract the length of the metadata block */ 328 data = bvec_virt(bvec); 329 length = data[offset]; 330 if (offset < bvec->bv_len - 1) { 331 length |= data[offset + 1] << 8; 332 } else { 333 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 334 res = -EIO; 335 goto out_free_bio; 336 } 337 data = bvec_virt(bvec); 338 length |= data[0] << 8; 339 } 340 bio_free_pages(bio); 341 bio_uninit(bio); 342 kfree(bio); 343 344 compressed = SQUASHFS_COMPRESSED(length); 345 length = SQUASHFS_COMPRESSED_SIZE(length); 346 index += 2; 347 348 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2, 349 compressed ? "" : "un", length); 350 } 351 if (length <= 0 || length > output->length || 352 (index + length) > msblk->bytes_used) { 353 res = -EIO; 354 goto out; 355 } 356 357 if (next_index) 358 *next_index = index + length; 359 360 res = squashfs_bio_read(sb, index, length, &bio, &offset); 361 if (res) 362 goto out; 363 364 if (compressed) { 365 if (!msblk->stream) { 366 res = -EIO; 367 goto out_free_bio; 368 } 369 res = msblk->thread_ops->decompress(msblk, bio, offset, length, output); 370 } else { 371 res = copy_bio_to_actor(bio, output, offset, length); 372 } 373 374 out_free_bio: 375 bio_free_pages(bio); 376 bio_uninit(bio); 377 kfree(bio); 378 out: 379 if (res < 0) { 380 ERROR("Failed to read block 0x%llx: %d\n", index, res); 381 if (msblk->panic_on_errors) 382 panic("squashfs read failed"); 383 } 384 385 return res; 386 } 387