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Message-ID: <a8b82109-fde6-3b6f-a911-981722223197@linux.alibaba.com>
Date: Sun, 30 Jul 2023 22:05:08 +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 22:01, Chao Yu wrote:
> On 2023/7/30 21:49, Gao Xiang wrote:
>>
>>
>> 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.
>
> strm is not in z_erofs_deflate_head list yet?
>
> Thanks
>
>>
>> Thanks,
>> Gao Xiang
>>
>>>
>>> Thanks,
>>>
>>>> + goto out_failed;
>>>> +
>>>> + spin_lock(&z_erofs_deflate_lock);
>>>> + strm->next = z_erofs_deflate_head;
>>>> + z_erofs_deflate_head = strm;
z_erofs_deflate_head will be added in each turn here.
Thanks,
Gao Xiang
>>>> + 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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