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Message-ID: <07c85385-be34-8fdc-876c-dc97639c5643@linux.alibaba.com>
Date: Sun, 30 Jul 2023 21:49:27 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Chao Yu <chao@...nel.org>, linux-erofs@...ts.ozlabs.org
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] erofs: DEFLATE compression support
On 2023/7/30 20:53, Chao Yu wrote:
> On 2023/7/16 17:19, Gao Xiang wrote:
>> Add DEFLATE compression as the 3rd supported algorithm.
>>
>> DEFLATE is a popular generic-purpose compression algorithm for quite
>> long time (many advanced formats like gzip, zlib, zip, png are all
>> based on that) as Apple documentation written "If you require
>> interoperability with non-Apple devices, use COMPRESSION_ZLIB. [1]".
>>
>> Due to its popularity, there are several hardware on-market DEFLATE
>> accelerators, such as (s390) DFLTCC, (Intel) IAA/QAT, (HiSilicon) ZIP
>> accelerator, etc. In addition, there are also several high-performence
>> IP cores and even open-source FPGA approches available for DEFLATE.
>> Therefore, it's useful to support DEFLATE compression in order to find
>> a way to utilize these accelerators for asynchronous I/Os and get
>> benefits from these later.
>>
>> Besides, it's a good choice to trade off between compression ratios
>> and performance compared to LZ4 and LZMA. The DEFLATE core format is
>> simple as well as easy to understand, therefore the code size of its
>> decompressor is small even for the bootloader use cases. The runtime
>> memory consumption is quite limited too (e.g. 32K + ~7K for each zlib
>> stream). As usual, EROFS ourperforms similar approaches too.
>>
>> Alternatively, DEFLATE could still be used for some specific files
>> since EROFS supports multiple compression algorithms in one image.
>>
>> [1] https://developer.apple.com/documentation/compression/compression_algorithm
>> ---
>> changes since v3:
>> - fix 'insz' mis-calculation, which leads to failure on 4k pclusters.
>>
>> fs/erofs/Kconfig | 15 ++
>> fs/erofs/Makefile | 1 +
>> fs/erofs/compress.h | 2 +
>> fs/erofs/decompressor.c | 6 +
>> fs/erofs/decompressor_deflate.c | 250 ++++++++++++++++++++++++++++++++
>> fs/erofs/erofs_fs.h | 7 +
>> fs/erofs/internal.h | 20 +++
>> fs/erofs/super.c | 10 ++
>> fs/erofs/zmap.c | 5 +-
>> 9 files changed, 314 insertions(+), 2 deletions(-)
>> create mode 100644 fs/erofs/decompressor_deflate.c
>>
>> diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
>> index f259d92c9720..56a99ba8ce22 100644
>> --- a/fs/erofs/Kconfig
>> +++ b/fs/erofs/Kconfig
>> @@ -99,6 +99,21 @@ config EROFS_FS_ZIP_LZMA
>> If unsure, say N.
>> +config EROFS_FS_ZIP_DEFLATE
>> + bool "EROFS DEFLATE compressed data support"
>> + depends on EROFS_FS_ZIP
>> + select ZLIB_INFLATE
>> + help
>> + Saying Y here includes support for reading EROFS file systems
>> + containing DEFLATE compressed data. It gives better compression
>> + ratios than the default LZ4 format, while it costs more CPU
>> + overhead.
>> +
>> + DEFLATE support is an experimental feature for now and so most
>> + file systems will be readable without selecting this option.
>> +
>> + If unsure, say N.
>> +
>> config EROFS_FS_ONDEMAND
>> bool "EROFS fscache-based on-demand read support"
>> depends on CACHEFILES_ONDEMAND && (EROFS_FS=m && FSCACHE || EROFS_FS=y && FSCACHE=y)
>> diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
>> index a3a98fc3e481..994d0b9deddf 100644
>> --- a/fs/erofs/Makefile
>> +++ b/fs/erofs/Makefile
>> @@ -5,4 +5,5 @@ erofs-objs := super.o inode.o data.o namei.o dir.o utils.o sysfs.o
>> erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
>> erofs-$(CONFIG_EROFS_FS_ZIP) += decompressor.o zmap.o zdata.o pcpubuf.o
>> erofs-$(CONFIG_EROFS_FS_ZIP_LZMA) += decompressor_lzma.o
>> +erofs-$(CONFIG_EROFS_FS_ZIP_DEFLATE) += decompressor_deflate.o
>> erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o
>> diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
>> index b1b846504027..349c3316ae6b 100644
>> --- a/fs/erofs/compress.h
>> +++ b/fs/erofs/compress.h
>> @@ -94,4 +94,6 @@ extern const struct z_erofs_decompressor erofs_decompressors[];
>> /* prototypes for specific algorithms */
>> int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
>> struct page **pagepool);
>> +int z_erofs_deflate_decompress(struct z_erofs_decompress_req *rq,
>> + struct page **pagepool);
>> #endif
>> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
>> index cfad1eac7fd9..332ec5f74002 100644
>> --- a/fs/erofs/decompressor.c
>> +++ b/fs/erofs/decompressor.c
>> @@ -379,4 +379,10 @@ const struct z_erofs_decompressor erofs_decompressors[] = {
>> .name = "lzma"
>> },
>> #endif
>> +#ifdef CONFIG_EROFS_FS_ZIP_DEFLATE
>> + [Z_EROFS_COMPRESSION_DEFLATE] = {
>> + .decompress = z_erofs_deflate_decompress,
>> + .name = "deflate"
>> + },
>> +#endif
>> };
>> diff --git a/fs/erofs/decompressor_deflate.c b/fs/erofs/decompressor_deflate.c
>> new file mode 100644
>> index 000000000000..c34e29b15465
>> --- /dev/null
>> +++ b/fs/erofs/decompressor_deflate.c
>> @@ -0,0 +1,250 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +#include <linux/module.h>
>> +#include <linux/zlib.h>
>> +#include "compress.h"
>> +
>> +struct z_erofs_deflate {
>> + struct z_erofs_deflate *next;
>> + struct z_stream_s z;
>> + u8 bounce[PAGE_SIZE];
>> +};
>> +
>> +static DEFINE_SPINLOCK(z_erofs_deflate_lock);
>> +static unsigned int z_erofs_deflate_nstrms, z_erofs_deflate_avail_strms;
>> +static struct z_erofs_deflate *z_erofs_deflate_head;
>> +static DECLARE_WAIT_QUEUE_HEAD(z_erofs_deflate_wq);
>> +
>> +module_param_named(deflate_streams, z_erofs_deflate_nstrms, uint, 0444);
>> +
>> +void z_erofs_deflate_exit(void)
>> +{
>> + /* there should be no running fs instance */
>> + while (z_erofs_deflate_avail_strms) {
>> + struct z_erofs_deflate *strm;
>> +
>> + spin_lock(&z_erofs_deflate_lock);
>> + strm = z_erofs_deflate_head;
>> + if (!strm) {
>> + spin_unlock(&z_erofs_deflate_lock);
>> + DBG_BUGON(1);
>> + return;
>> + }
>> + z_erofs_deflate_head = NULL;
>> + spin_unlock(&z_erofs_deflate_lock);
>> +
>> + while (strm) {
>> + struct z_erofs_deflate *n = strm->next;
>> +
>> + vfree(strm->z.workspace);
>> + kfree(strm);
>> + --z_erofs_deflate_avail_strms;
>> + strm = n;
>> + }
>> + }
>> +}
>> +
>> +int __init z_erofs_deflate_init(void)
>> +{
>> + /* by default, use # of possible CPUs instead */
>> + if (!z_erofs_deflate_nstrms)
>> + z_erofs_deflate_nstrms = num_possible_cpus();
>> +
>> + for (; z_erofs_deflate_avail_strms < z_erofs_deflate_nstrms;
>> + ++z_erofs_deflate_avail_strms) {
>> + struct z_erofs_deflate *strm;
>> +
>> + strm = kzalloc(sizeof(*strm), GFP_KERNEL);
>> + if (!strm)
>> + goto out_failed;
>> +
>> + /* XXX: in-kernel zlib cannot shrink windowbits currently */
>> + strm->z.workspace = vmalloc(zlib_inflate_workspacesize());
>> + if (!strm->z.workspace)
>
> kfree(strm)?
z_erofs_deflate_exit() below will handle this.
Thanks,
Gao Xiang
>
> Thanks,
>
>> + goto out_failed;
>> +
>> + spin_lock(&z_erofs_deflate_lock);
>> + strm->next = z_erofs_deflate_head;
>> + z_erofs_deflate_head = strm;
>> + spin_unlock(&z_erofs_deflate_lock);
>> + }
>> + return 0;
>> +
>> +out_failed:
>> + pr_err("failed to allocate zlib workspace\n");
>> + z_erofs_deflate_exit();
>> + return -ENOMEM;
>> +}
>> +
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