1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * Squashfs - a compressed read only filesystem for Linux
12  * This file implements the low-level routines to read and decompress
31  * Returns the amount of bytes copied to the page actor.
35 			     int offset, int req_length)  in copy_bio_to_actor()  argument
50 		int bytes_to_copy = min_t(int, bvec->bv_len - offset,  in copy_bio_to_actor()
51 					  PAGE_SIZE - actor_offset);  in copy_bio_to_actor()
54 				      req_length - copied_bytes);  in copy_bio_to_actor()
57 					offset, bytes_to_copy);  in copy_bio_to_actor()
61 		offset += bytes_to_copy;  in copy_bio_to_actor()
69 		if (offset >= bvec->bv_len) {  in copy_bio_to_actor()
72 			offset = 0;  in copy_bio_to_actor()
83 	struct page *head_to_cache = NULL, *tail_to_cache = NULL;  in squashfs_bio_read_cached()
84 	struct block_device *bdev = fullbio->bi_bdev;  in squashfs_bio_read_cached()
93 		struct page *page = bv->bv_page;  in squashfs_bio_read_cached()  local
95 		if (page->mapping == cache_mapping) {  in squashfs_bio_read_cached()
102 		 * the page size, so read_start and read_end cover full pages.  in squashfs_bio_read_cached()
110 			head_to_cache = page;  in squashfs_bio_read_cached()
111 		else if (idx == page_count - 1 && index + length != read_end)  in squashfs_bio_read_cached()
112 			tail_to_cache = page;  in squashfs_bio_read_cached()
120 					 (end_idx - start_idx) * PAGE_SECTORS);  in squashfs_bio_read_cached()
135 			 (end_idx - start_idx) * PAGE_SECTORS);  in squashfs_bio_read_cached()
157 						(read_end >> PAGE_SHIFT) - 1,  in squashfs_bio_read_cached()
169 static struct page *squashfs_get_cache_page(struct address_space *mapping,  in squashfs_get_cache_page()
172 	struct page *page;  in squashfs_get_cache_page()  local
177 	page = find_get_page(mapping, index);  in squashfs_get_cache_page()
178 	if (!page)  in squashfs_get_cache_page()
181 	if (!PageUptodate(page)) {  in squashfs_get_cache_page()
182 		put_page(page);  in squashfs_get_cache_page()
186 	return page;  in squashfs_get_cache_page()
192 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_bio_read()
193 	struct address_space *cache_mapping = msblk->cache_mapping;  in squashfs_bio_read()
194 	const u64 read_start = round_down(index, msblk->devblksize);  in squashfs_bio_read()
195 	const sector_t block = read_start >> msblk->devblksize_log2;  in squashfs_bio_read()
196 	const u64 read_end = round_up(index + length, msblk->devblksize);  in squashfs_bio_read()
197 	const sector_t block_end = read_end >> msblk->devblksize_log2;  in squashfs_bio_read()
198 	int offset = read_start - round_down(index, PAGE_SIZE);  in squashfs_bio_read()  local
199 	int total_len = (block_end - block) << msblk->devblksize_log2;  in squashfs_bio_read()
200 	const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);  in squashfs_bio_read()
206 		return -ENOMEM;  in squashfs_bio_read()
207 	bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);  in squashfs_bio_read()
208 	bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);  in squashfs_bio_read()
212 			min_t(unsigned int, PAGE_SIZE - offset, total_len);  in squashfs_bio_read()
214 		struct page *page;  in squashfs_bio_read()  local
216 		page = squashfs_get_cache_page(cache_mapping, index);  in squashfs_bio_read()
217 		if (!page)  in squashfs_bio_read()
218 			page = alloc_page(GFP_NOIO);  in squashfs_bio_read()
220 		if (!page) {  in squashfs_bio_read()
221 			error = -ENOMEM;  in squashfs_bio_read()
226 		 * Use the __ version to avoid merging since we need each page  in squashfs_bio_read()
229 		__bio_add_page(bio, page, len, offset);  in squashfs_bio_read()
230 		offset = 0;  in squashfs_bio_read()
231 		total_len -= len;  in squashfs_bio_read()
244 	*block_offset = index & ((1 << msblk->devblksize_log2) - 1);  in squashfs_bio_read()
255  * Read and decompress a metadata block or datablock.  Length is non-zero
260  * generated a larger block - this does occasionally happen with compression
266 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_read_data()
270 	int offset;  in squashfs_read_data()  local
279 			index, compressed ? "" : "un", length, output->length);  in squashfs_read_data()
288 		if (index + 2 > msblk->bytes_used) {  in squashfs_read_data()
289 			res = -EIO;  in squashfs_read_data()
292 		res = squashfs_bio_read(sb, index, 2, &bio, &offset);  in squashfs_read_data()
297 			res = -EIO;  in squashfs_read_data()
302 		length = data[offset];  in squashfs_read_data()
303 		if (offset < bvec->bv_len - 1) {  in squashfs_read_data()
304 			length |= data[offset + 1] << 8;  in squashfs_read_data()
307 				res = -EIO;  in squashfs_read_data()
321 		TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,  in squashfs_read_data()
324 	if (length <= 0 || length > output->length ||  in squashfs_read_data()
325 			(index + length) > msblk->bytes_used) {  in squashfs_read_data()
326 		res = -EIO;  in squashfs_read_data()
333 	res = squashfs_bio_read(sb, index, length, &bio, &offset);  in squashfs_read_data()
338 		if (!msblk->stream) {  in squashfs_read_data()
339 			res = -EIO;  in squashfs_read_data()
342 		res = msblk->thread_ops->decompress(msblk, bio, offset, length, output);  in squashfs_read_data()
344 		res = copy_bio_to_actor(bio, output, offset, length);  in squashfs_read_data()
354 		if (msblk->panic_on_errors)  in squashfs_read_data()