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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Squashfs - a compressed read only filesystem for Linux4 *5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 20086 * Phillip Lougher <phillip@squashfs.org.uk>7 *8 * block.c9 */10 11/*12 * This file implements the low-level routines to read and decompress13 * 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 */33static 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 79static 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 as102 * the page size, so read_start and read_end cover full pages.103 *104 * Compare these to the original required index and length to105 * only cache pages which were requested partially, since these106 * are the ones which are likely to be needed when reading107 * 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 169static 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 189static 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 bio = bio_kmalloc(page_count, GFP_NOIO);205 if (!bio)206 return -ENOMEM;207 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);208 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);209 210 for (i = 0; i < page_count; ++i) {211 unsigned int len =212 min_t(unsigned int, PAGE_SIZE - offset, total_len);213 pgoff_t index = (read_start >> PAGE_SHIFT) + i;214 struct page *page;215 216 page = squashfs_get_cache_page(cache_mapping, index);217 if (!page)218 page = alloc_page(GFP_NOIO);219 220 if (!page) {221 error = -ENOMEM;222 goto out_free_bio;223 }224 225 /*226 * Use the __ version to avoid merging since we need each page227 * to be separate when we check for and avoid cached pages.228 */229 __bio_add_page(bio, page, len, offset);230 offset = 0;231 total_len -= len;232 }233 234 if (cache_mapping)235 error = squashfs_bio_read_cached(bio, cache_mapping, index,236 length, read_start, read_end,237 page_count);238 else239 error = submit_bio_wait(bio);240 if (error)241 goto out_free_bio;242 243 *biop = bio;244 *block_offset = index & ((1 << msblk->devblksize_log2) - 1);245 return 0;246 247out_free_bio:248 bio_free_pages(bio);249 bio_uninit(bio);250 kfree(bio);251 return error;252}253 254/*255 * Read and decompress a metadata block or datablock. Length is non-zero256 * if a datablock is being read (the size is stored elsewhere in the257 * filesystem), otherwise the length is obtained from the first two bytes of258 * the metadata block. A bit in the length field indicates if the block259 * is stored uncompressed in the filesystem (usually because compression260 * generated a larger block - this does occasionally happen with compression261 * algorithms).262 */263int squashfs_read_data(struct super_block *sb, u64 index, int length,264 u64 *next_index, struct squashfs_page_actor *output)265{266 struct squashfs_sb_info *msblk = sb->s_fs_info;267 struct bio *bio = NULL;268 int compressed;269 int res;270 int offset;271 272 if (length) {273 /*274 * Datablock.275 */276 compressed = SQUASHFS_COMPRESSED_BLOCK(length);277 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);278 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",279 index, compressed ? "" : "un", length, output->length);280 } else {281 /*282 * Metadata block.283 */284 const u8 *data;285 struct bvec_iter_all iter_all = {};286 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);287 288 if (index + 2 > msblk->bytes_used) {289 res = -EIO;290 goto out;291 }292 res = squashfs_bio_read(sb, index, 2, &bio, &offset);293 if (res)294 goto out;295 296 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {297 res = -EIO;298 goto out_free_bio;299 }300 /* Extract the length of the metadata block */301 data = bvec_virt(bvec);302 length = data[offset];303 if (offset < bvec->bv_len - 1) {304 length |= data[offset + 1] << 8;305 } else {306 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {307 res = -EIO;308 goto out_free_bio;309 }310 data = bvec_virt(bvec);311 length |= data[0] << 8;312 }313 bio_free_pages(bio);314 bio_uninit(bio);315 kfree(bio);316 317 compressed = SQUASHFS_COMPRESSED(length);318 length = SQUASHFS_COMPRESSED_SIZE(length);319 index += 2;320 321 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,322 compressed ? "" : "un", length);323 }324 if (length <= 0 || length > output->length ||325 (index + length) > msblk->bytes_used) {326 res = -EIO;327 goto out;328 }329 330 if (next_index)331 *next_index = index + length;332 333 res = squashfs_bio_read(sb, index, length, &bio, &offset);334 if (res)335 goto out;336 337 if (compressed) {338 if (!msblk->stream) {339 res = -EIO;340 goto out_free_bio;341 }342 res = msblk->thread_ops->decompress(msblk, bio, offset, length, output);343 } else {344 res = copy_bio_to_actor(bio, output, offset, length);345 }346 347out_free_bio:348 bio_free_pages(bio);349 bio_uninit(bio);350 kfree(bio);351out:352 if (res < 0) {353 ERROR("Failed to read block 0x%llx: %d\n", index, res);354 if (msblk->panic_on_errors)355 panic("squashfs read failed");356 }357 358 return res;359}360