fs/squashfs/block.c - linux - Git at Google

 // 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 page *head_to_cache = NULL, *tail_to_cache = NULL;
 	struct block_device *bdev = fullbio->bi_bdev;
 	int start_idx = 0, end_idx = 0;
 	struct bvec_iter_all iter_all;
 	struct bio *bio = NULL;
 	struct bio_vec *bv;
 	int idx = 0;
 	int err = 0;

 	bio_for_each_segment_all(bv, fullbio, iter_all) {
 		struct page *page = bv->bv_page;

 		if (page->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 = page;
 		else if (idx == page_count - 1 && index + length != read_end)
 			tail_to_cache = page;

 		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 = add_to_page_cache_lru(head_to_cache, cache_mapping,
 						read_start >> PAGE_SHIFT,
 						GFP_NOIO);

 		if (!ret) {
 			SetPageUptodate(head_to_cache);
 			unlock_page(head_to_cache);
 		}

 	}

 	if (tail_to_cache) {
 		int ret = add_to_page_cache_lru(tail_to_cache, cache_mapping,
 						(read_end >> PAGE_SHIFT) - 1,
 						GFP_NOIO);

 		if (!ret) {
 			SetPageUptodate(tail_to_cache);
 			unlock_page(tail_to_cache);
 		}
 	}

 	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(bio, sb->s_bdev, bio->bi_inline_vecs, 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;
 }
	// 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 page head_to_cache = NULL, tail_to_cache = NULL;
	struct block_device *bdev = fullbio->bi_bdev;
	int start_idx = 0, end_idx = 0;
	struct bvec_iter_all iter_all;
	struct bio *bio = NULL;
	struct bio_vec *bv;
	int idx = 0;
	int err = 0;

	bio_for_each_segment_all(bv, fullbio, iter_all) {
	struct page *page = bv->bv_page;

	if (page->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 = page;
	else if (idx == page_count - 1 && index + length != read_end)
	tail_to_cache = page;

	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 = add_to_page_cache_lru(head_to_cache, cache_mapping,
	read_start >> PAGE_SHIFT,
	GFP_NOIO);

	if (!ret) {
	SetPageUptodate(head_to_cache);
	unlock_page(head_to_cache);
	}

	}

	if (tail_to_cache) {
	int ret = add_to_page_cache_lru(tail_to_cache, cache_mapping,
	(read_end >> PAGE_SHIFT) - 1,
	GFP_NOIO);

	if (!ret) {
	SetPageUptodate(tail_to_cache);
	unlock_page(tail_to_cache);
	}
	}

	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(bio, sb->s_bdev, bio->bi_inline_vecs, 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;
	}