// 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 <[email protected]>
*
* 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;
}
Codebase Browser
linux