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Message-ID: <f6210979-4322-feb9-9f22-76f4cb1a33da@kernel.org>
Date:   Sun, 30 Jul 2023 22:01:52 +0800
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Subject: Re: [PATCH v4] erofs: DEFLATE compression support
Content-Language: en-US
To:     Gao Xiang <hsiangkao@linux.alibaba.com>,
        linux-erofs@lists.ozlabs.org
Cc:     LKML <linux-kernel@vger.kernel.org>
References: <20230713001441.30462-1-hsiangkao@linux.alibaba.com>
 <20230716091940.40899-1-hsiangkao@linux.alibaba.com>
 <9570176a-02c2-c500-14c6-b8ca220cfb96@kernel.org>
 <07c85385-be34-8fdc-876c-dc97639c5643@linux.alibaba.com>
From:   Chao Yu <chao@kernel.org>
In-Reply-To: <07c85385-be34-8fdc-876c-dc97639c5643@linux.alibaba.com>
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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;
>>> +        spin_unlock(&z_erofs_deflate_lock);
>>> +    }
>>> +    return 0;
>>> +
>>> +out_failed:
>>> +    pr_err("failed to allocate zlib workspace\n");
>>> +    z_erofs_deflate_exit();
>>> +    return -ENOMEM;
>>> +}
>>> +