linux/fs/squashfs/block.c
Philippe Liard 93e72b3c61 squashfs: migrate from ll_rw_block usage to BIO
ll_rw_block() function has been deprecated in favor of BIO which appears
to come with large performance improvements.

This patch decreases boot time by close to 40% when using squashfs for
the root file-system.  This is observed at least in the context of
starting an Android VM on Chrome OS using crosvm.  The patch was tested
on 4.19 as well as master.

This patch is largely based on Adrien Schildknecht's patch that was
originally sent as https://lkml.org/lkml/2017/9/22/814 though with some
significant changes and simplifications while also taking Phillip
Lougher's feedback into account, around preserving support for
FILE_CACHE in particular.

[akpm@linux-foundation.org: fix build error reported by Randy]
  Link: http://lkml.kernel.org/r/319997c2-5fc8-f889-2ea3-d913308a7c1f@infradead.org
Signed-off-by: Philippe Liard <pliard@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Adrien Schildknecht <adrien+dev@schischi.me>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Daniel Rosenberg <drosen@google.com>
Link: https://chromium.googlesource.com/chromiumos/platform/crosvm
Link: http://lkml.kernel.org/r/20191106074238.186023-1-pliard@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-02 10:59:05 -07:00

224 lines
5.6 KiB
C

// 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/string.h>
#include <linux/buffer_head.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 = squashfs_first_page(actor);
struct bvec_iter_all iter_all = {};
struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
int copied_bytes = 0;
int actor_offset = 0;
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);
memcpy(actor_addr + actor_offset,
page_address(bvec->bv_page) + bvec->bv_offset + 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(struct super_block *sb, u64 index, int length,
struct bio **biop, int *block_offset)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
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_alloc(GFP_NOIO, page_count);
if (!bio)
return -ENOMEM;
bio_set_dev(bio, sb->s_bdev);
bio->bi_opf = 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);
struct page *page = alloc_page(GFP_NOIO);
if (!page) {
error = -ENOMEM;
goto out_free_bio;
}
if (!bio_add_page(bio, page, len, offset)) {
error = -EIO;
goto out_free_bio;
}
offset = 0;
total_len -= len;
}
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_put(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 = page_address(bvec->bv_page) + bvec->bv_offset;
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 = page_address(bvec->bv_page) + bvec->bv_offset;
length |= data[0] << 8;
}
bio_free_pages(bio);
bio_put(bio);
compressed = SQUASHFS_COMPRESSED(length);
length = SQUASHFS_COMPRESSED_SIZE(length);
index += 2;
TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
compressed ? "" : "un", length);
}
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 = squashfs_decompress(msblk, bio, offset, length, output);
} else {
res = copy_bio_to_actor(bio, output, offset, length);
}
out_free_bio:
bio_free_pages(bio);
bio_put(bio);
out:
if (res < 0)
ERROR("Failed to read block 0x%llx: %d\n", index, res);
return res;
}