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 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_alloc_clone(bdev, 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 } 168 169 static int squashfs_bio_read(struct super_block *sb, u64 index, int length, 170 struct bio **biop, int *block_offset) 171 { 172 struct squashfs_sb_info *msblk = sb->s_fs_info; 173 struct address_space *cache_mapping = msblk->cache_mapping; 174 const u64 read_start = round_down(index, msblk->devblksize); 175 const sector_t block = read_start >> msblk->devblksize_log2; 176 const u64 read_end = round_up(index + length, msblk->devblksize); 177 const sector_t block_end = read_end >> msblk->devblksize_log2; 178 int offset = read_start - round_down(index, PAGE_SIZE); 179 int total_len = (block_end - block) << msblk->devblksize_log2; 180 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE); 181 int error, i; 182 struct bio *bio; 183 184 bio = bio_kmalloc(page_count, GFP_NOIO); 185 if (!bio) 186 return -ENOMEM; 187 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ); 188 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 189 190 for (i = 0; i < page_count; ++i) { 191 unsigned int len = 192 min_t(unsigned int, PAGE_SIZE - offset, total_len); 193 struct page *page = NULL; 194 195 if (cache_mapping) 196 page = find_get_page(cache_mapping, 197 (read_start >> PAGE_SHIFT) + i); 198 if (!page) 199 page = alloc_page(GFP_NOIO); 200 201 if (!page) { 202 error = -ENOMEM; 203 goto out_free_bio; 204 } 205 206 /* 207 * Use the __ version to avoid merging since we need each page 208 * to be separate when we check for and avoid cached pages. 209 */ 210 __bio_add_page(bio, page, len, offset); 211 offset = 0; 212 total_len -= len; 213 } 214 215 if (cache_mapping) 216 error = squashfs_bio_read_cached(bio, cache_mapping, index, 217 length, read_start, read_end, 218 page_count); 219 else 220 error = submit_bio_wait(bio); 221 if (error) 222 goto out_free_bio; 223 224 *biop = bio; 225 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 226 return 0; 227 228 out_free_bio: 229 bio_free_pages(bio); 230 bio_uninit(bio); 231 kfree(bio); 232 return error; 233 } 234 235 /* 236 * Read and decompress a metadata block or datablock. Length is non-zero 237 * if a datablock is being read (the size is stored elsewhere in the 238 * filesystem), otherwise the length is obtained from the first two bytes of 239 * the metadata block. A bit in the length field indicates if the block 240 * is stored uncompressed in the filesystem (usually because compression 241 * generated a larger block - this does occasionally happen with compression 242 * algorithms). 243 */ 244 int squashfs_read_data(struct super_block *sb, u64 index, int length, 245 u64 *next_index, struct squashfs_page_actor *output) 246 { 247 struct squashfs_sb_info *msblk = sb->s_fs_info; 248 struct bio *bio = NULL; 249 int compressed; 250 int res; 251 int offset; 252 253 if (length) { 254 /* 255 * Datablock. 256 */ 257 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 258 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 259 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 260 index, compressed ? "" : "un", length, output->length); 261 } else { 262 /* 263 * Metadata block. 264 */ 265 const u8 *data; 266 struct bvec_iter_all iter_all = {}; 267 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 268 269 if (index + 2 > msblk->bytes_used) { 270 res = -EIO; 271 goto out; 272 } 273 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 274 if (res) 275 goto out; 276 277 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 278 res = -EIO; 279 goto out_free_bio; 280 } 281 /* Extract the length of the metadata block */ 282 data = bvec_virt(bvec); 283 length = data[offset]; 284 if (offset < bvec->bv_len - 1) { 285 length |= data[offset + 1] << 8; 286 } else { 287 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 288 res = -EIO; 289 goto out_free_bio; 290 } 291 data = bvec_virt(bvec); 292 length |= data[0] << 8; 293 } 294 bio_free_pages(bio); 295 bio_uninit(bio); 296 kfree(bio); 297 298 compressed = SQUASHFS_COMPRESSED(length); 299 length = SQUASHFS_COMPRESSED_SIZE(length); 300 index += 2; 301 302 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2, 303 compressed ? "" : "un", length); 304 } 305 if (length < 0 || length > output->length || 306 (index + length) > msblk->bytes_used) { 307 res = -EIO; 308 goto out; 309 } 310 311 if (next_index) 312 *next_index = index + length; 313 314 res = squashfs_bio_read(sb, index, length, &bio, &offset); 315 if (res) 316 goto out; 317 318 if (compressed) { 319 if (!msblk->stream) { 320 res = -EIO; 321 goto out_free_bio; 322 } 323 res = msblk->thread_ops->decompress(msblk, bio, offset, length, output); 324 } else { 325 res = copy_bio_to_actor(bio, output, offset, length); 326 } 327 328 out_free_bio: 329 bio_free_pages(bio); 330 bio_uninit(bio); 331 kfree(bio); 332 out: 333 if (res < 0) { 334 ERROR("Failed to read block 0x%llx: %d\n", index, res); 335 if (msblk->panic_on_errors) 336 panic("squashfs read failed"); 337 } 338 339 return res; 340 } 341