// SPDX-License-Identifier: GPL-2.0-or-later/* * Squashfs - a compressed read only filesystem for Linux * * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 * Phillip Lougher <phillip@squashfs.org.uk> * * block.c */ /* * This file implements the low-level routines to read and decompress * datablocks and metadata blocks. */ #include <linux/blkdev.h>#include <linux/fs.h>#include <linux/vfs.h>#include <linux/slab.h>#include <linux/pagemap.h>#include <linux/string.h>#include <linux/bio.h> #include "squashfs_fs.h"#include "squashfs_fs_sb.h"#include "squashfs.h"#include "decompressor.h"#include "page_actor.h" /* * Returns the amount of bytes copied to the page actor. */static int copy_bio_to_actor(struct bio *bio,			     struct squashfs_page_actor *actor,			     int offset, int req_length){	void *actor_addr;	struct bvec_iter_all iter_all = {};	struct bio_vec *bvec = bvec_init_iter_all(&iter_all);	int copied_bytes = 0;	int actor_offset = 0; 	squashfs_actor_nobuff(actor);	actor_addr = squashfs_first_page(actor); 	if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))		return 0; 	while (copied_bytes < req_length) {		int bytes_to_copy = min_t(int, bvec->bv_len - offset,					  PAGE_SIZE - actor_offset); 		bytes_to_copy = min_t(int, bytes_to_copy,				      req_length - copied_bytes);		if (!IS_ERR(actor_addr))			memcpy(actor_addr + actor_offset, bvec_virt(bvec) +					offset, bytes_to_copy); 		actor_offset += bytes_to_copy;		copied_bytes += bytes_to_copy;		offset += bytes_to_copy; 		if (actor_offset >= PAGE_SIZE) {			actor_addr = squashfs_next_page(actor);			if (!actor_addr)				break;			actor_offset = 0;		}		if (offset >= bvec->bv_len) {			if (!bio_next_segment(bio, &iter_all))				break;			offset = 0;		}	}	squashfs_finish_page(actor);	return copied_bytes;} static int squashfs_bio_read_cached(struct bio *fullbio,		struct address_space *cache_mapping, u64 index, int length,		u64 read_start, u64 read_end, int page_count){	struct folio *head_to_cache = NULL, *tail_to_cache = NULL;	struct block_device *bdev = fullbio->bi_bdev;	int start_idx = 0, end_idx = 0;	struct folio_iter fi;	struct bio *bio = NULL;	int idx = 0;	int err = 0;#ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL	struct folio **cache_folios = kmalloc_objs(*cache_folios, page_count,						   GFP_KERNEL | __GFP_ZERO);#endif 	bio_for_each_folio_all(fi, fullbio) {		struct folio *folio = fi.folio; 		if (folio->mapping == cache_mapping) {			idx++;			continue;		} 		/*		 * We only use this when the device block size is the same as		 * the page size, so read_start and read_end cover full pages.		 *		 * Compare these to the original required index and length to		 * only cache pages which were requested partially, since these		 * are the ones which are likely to be needed when reading		 * adjacent blocks.		 */		if (idx == 0 && index != read_start)			head_to_cache = folio;		else if (idx == page_count - 1 && index + length != read_end)			tail_to_cache = folio;#ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL		/* Cache all pages in the BIO for repeated reads */		else if (cache_folios)			cache_folios[idx] = folio;#endif 		if (!bio || idx != end_idx) {			struct bio *new = bio_alloc_clone(bdev, fullbio,							  GFP_NOIO, &fs_bio_set); 			if (bio) {				bio_trim(bio, start_idx * PAGE_SECTORS,					 (end_idx - start_idx) * PAGE_SECTORS);				bio_chain(bio, new);				submit_bio(bio);			} 			bio = new;			start_idx = idx;		} 		idx++;		end_idx = idx;	} 	if (bio) {		bio_trim(bio, start_idx * PAGE_SECTORS,			 (end_idx - start_idx) * PAGE_SECTORS);		err = submit_bio_wait(bio);		bio_put(bio);	} 	if (err)		return err; 	if (head_to_cache) {		int ret = filemap_add_folio(cache_mapping, head_to_cache,						read_start >> PAGE_SHIFT,						GFP_NOIO); 		if (!ret) {			folio_mark_uptodate(head_to_cache);			folio_unlock(head_to_cache);		} 	} 	if (tail_to_cache) {		int ret = filemap_add_folio(cache_mapping, tail_to_cache,						(read_end >> PAGE_SHIFT) - 1,						GFP_NOIO); 		if (!ret) {			folio_mark_uptodate(tail_to_cache);			folio_unlock(tail_to_cache);		}	} #ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL	if (!cache_folios)		goto out; 	for (idx = 0; idx < page_count; idx++) {		if (!cache_folios[idx])			continue;		int ret = filemap_add_folio(cache_mapping, cache_folios[idx],						(read_start >> PAGE_SHIFT) + idx,						GFP_NOIO); 		if (!ret) {			folio_mark_uptodate(cache_folios[idx]);			folio_unlock(cache_folios[idx]);		}	}	kfree(cache_folios);out:#endif	return 0;} static struct page *squashfs_get_cache_page(struct address_space *mapping,					    pgoff_t index){	struct page *page; 	if (!mapping)		return NULL; 	page = find_get_page(mapping, index);	if (!page)		return NULL; 	if (!PageUptodate(page)) {		put_page(page);		return NULL;	} 	return page;} static int squashfs_bio_read(struct super_block *sb, u64 index, int length,			     struct bio **biop, int *block_offset){	struct squashfs_sb_info *msblk = sb->s_fs_info;	struct address_space *cache_mapping = msblk->cache_mapping;	const u64 read_start = round_down(index, msblk->devblksize);	const sector_t block = read_start >> msblk->devblksize_log2;	const u64 read_end = round_up(index + length, msblk->devblksize);	const sector_t block_end = read_end >> msblk->devblksize_log2;	int offset = read_start - round_down(index, PAGE_SIZE);	int total_len = (block_end - block) << msblk->devblksize_log2;	const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);	int error, i;	struct bio *bio; 	bio = bio_kmalloc(page_count, GFP_NOIO);	if (!bio)		return -ENOMEM;	bio_init_inline(bio, sb->s_bdev, page_count, REQ_OP_READ);	bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 	for (i = 0; i < page_count; ++i) {		unsigned int len =			min_t(unsigned int, PAGE_SIZE - offset, total_len);		pgoff_t index = (read_start >> PAGE_SHIFT) + i;		struct page *page; 		page = squashfs_get_cache_page(cache_mapping, index);		if (!page)			page = alloc_page(GFP_NOIO); 		if (!page) {			error = -ENOMEM;			goto out_free_bio;		} 		/*		 * Use the __ version to avoid merging since we need each page		 * to be separate when we check for and avoid cached pages.		 */		__bio_add_page(bio, page, len, offset);		offset = 0;		total_len -= len;	} 	if (cache_mapping)		error = squashfs_bio_read_cached(bio, cache_mapping, index,						 length, read_start, read_end,						 page_count);	else		error = submit_bio_wait(bio);	if (error)		goto out_free_bio; 	*biop = bio;	*block_offset = index & ((1 << msblk->devblksize_log2) - 1);	return 0; out_free_bio:	bio_free_pages(bio);	bio_uninit(bio);	kfree(bio);	return error;} /* * Read and decompress a metadata block or datablock.  Length is non-zero * if a datablock is being read (the size is stored elsewhere in the * filesystem), otherwise the length is obtained from the first two bytes of * the metadata block.  A bit in the length field indicates if the block * is stored uncompressed in the filesystem (usually because compression * generated a larger block - this does occasionally happen with compression * algorithms). */int squashfs_read_data(struct super_block *sb, u64 index, int length,		       u64 *next_index, struct squashfs_page_actor *output){	struct squashfs_sb_info *msblk = sb->s_fs_info;	struct bio *bio = NULL;	int compressed;	int res;	int offset; 	if (length) {		/*		 * Datablock.		 */		compressed = SQUASHFS_COMPRESSED_BLOCK(length);		length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);		TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",			index, compressed ? "" : "un", length, output->length);	} else {		/*		 * Metadata block.		 */		const u8 *data;		struct bvec_iter_all iter_all = {};		struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 		if (index + 2 > msblk->bytes_used) {			res = -EIO;			goto out;		}		res = squashfs_bio_read(sb, index, 2, &bio, &offset);		if (res)			goto out; 		if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {			res = -EIO;			goto out_free_bio;		}		/* Extract the length of the metadata block */		data = bvec_virt(bvec);		length = data[offset];		if (offset < bvec->bv_len - 1) {			length |= data[offset + 1] << 8;		} else {			if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {				res = -EIO;				goto out_free_bio;			}			data = bvec_virt(bvec);			length |= data[0] << 8;		}		bio_free_pages(bio);		bio_uninit(bio);		kfree(bio); 		compressed = SQUASHFS_COMPRESSED(length);		length = SQUASHFS_COMPRESSED_SIZE(length);		index += 2; 		TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,		      compressed ? "" : "un", length);	}	if (length <= 0 || length > output->length ||			(index + length) > msblk->bytes_used) {		res = -EIO;		goto out;	} 	if (next_index)		*next_index = index + length; 	res = squashfs_bio_read(sb, index, length, &bio, &offset);	if (res)		goto out; 	if (compressed) {		if (!msblk->stream) {			res = -EIO;			goto out_free_bio;		}		res = msblk->thread_ops->decompress(msblk, bio, offset, length, output);	} else {		res = copy_bio_to_actor(bio, output, offset, length);	} out_free_bio:	bio_free_pages(bio);	bio_uninit(bio);	kfree(bio);out:	if (res < 0) {		ERROR("Failed to read block 0x%llx: %d\n", index, res);		if (msblk->panic_on_errors)			panic("squashfs read failed");	} 	return res;}