1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Squashfs - a compressed read only filesystem for Linux
5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
6 * Phillip Lougher <phillip@squashfs.org.uk>
12 * This file implements the low-level routines to read and decompress
13 * datablocks and metadata blocks.
16 #include <linux/blkdev.h>
18 #include <linux/vfs.h>
19 #include <linux/slab.h>
20 #include <linux/string.h>
21 #include <linux/buffer_head.h>
22 #include <linux/bio.h>
24 #include "squashfs_fs.h"
25 #include "squashfs_fs_sb.h"
27 #include "decompressor.h"
28 #include "page_actor.h"
31 * Returns the amount of bytes copied to the page actor.
33 static int copy_bio_to_actor(struct bio *bio,
34 struct squashfs_page_actor *actor,
35 int offset, int req_length)
38 struct bvec_iter_all iter_all = {};
39 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
43 squashfs_actor_nobuff(actor);
44 actor_addr = squashfs_first_page(actor);
46 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
49 while (copied_bytes < req_length) {
50 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
51 PAGE_SIZE - actor_offset);
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);
59 actor_offset += bytes_to_copy;
60 copied_bytes += bytes_to_copy;
61 offset += bytes_to_copy;
63 if (actor_offset >= PAGE_SIZE) {
64 actor_addr = squashfs_next_page(actor);
69 if (offset >= bvec->bv_len) {
70 if (!bio_next_segment(bio, &iter_all))
75 squashfs_finish_page(actor);
79 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
80 struct bio **biop, int *block_offset)
82 struct squashfs_sb_info *msblk = sb->s_fs_info;
83 const u64 read_start = round_down(index, msblk->devblksize);
84 const sector_t block = read_start >> msblk->devblksize_log2;
85 const u64 read_end = round_up(index + length, msblk->devblksize);
86 const sector_t block_end = read_end >> msblk->devblksize_log2;
87 int offset = read_start - round_down(index, PAGE_SIZE);
88 int total_len = (block_end - block) << msblk->devblksize_log2;
89 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
93 bio = bio_kmalloc(page_count, GFP_NOIO);
96 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);
97 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
99 for (i = 0; i < page_count; ++i) {
101 min_t(unsigned int, PAGE_SIZE - offset, total_len);
102 struct page *page = alloc_page(GFP_NOIO);
108 if (!bio_add_page(bio, page, len, offset)) {
116 error = submit_bio_wait(bio);
121 *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
132 * Read and decompress a metadata block or datablock. Length is non-zero
133 * if a datablock is being read (the size is stored elsewhere in the
134 * filesystem), otherwise the length is obtained from the first two bytes of
135 * the metadata block. A bit in the length field indicates if the block
136 * is stored uncompressed in the filesystem (usually because compression
137 * generated a larger block - this does occasionally happen with compression
140 int squashfs_read_data(struct super_block *sb, u64 index, int length,
141 u64 *next_index, struct squashfs_page_actor *output)
143 struct squashfs_sb_info *msblk = sb->s_fs_info;
144 struct bio *bio = NULL;
153 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
154 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
155 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
156 index, compressed ? "" : "un", length, output->length);
162 struct bvec_iter_all iter_all = {};
163 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
165 if (index + 2 > msblk->bytes_used) {
169 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
173 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
177 /* Extract the length of the metadata block */
178 data = bvec_virt(bvec);
179 length = data[offset];
180 if (offset < bvec->bv_len - 1) {
181 length |= data[offset + 1] << 8;
183 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
187 data = bvec_virt(bvec);
188 length |= data[0] << 8;
194 compressed = SQUASHFS_COMPRESSED(length);
195 length = SQUASHFS_COMPRESSED_SIZE(length);
198 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
199 compressed ? "" : "un", length);
201 if (length < 0 || length > output->length ||
202 (index + length) > msblk->bytes_used) {
208 *next_index = index + length;
210 res = squashfs_bio_read(sb, index, length, &bio, &offset);
215 if (!msblk->stream) {
219 res = msblk->thread_ops->decompress(msblk, bio, offset, length, output);
221 res = copy_bio_to_actor(bio, output, offset, length);
230 ERROR("Failed to read block 0x%llx: %d\n", index, res);
231 if (msblk->panic_on_errors)
232 panic("squashfs read failed");