linux-kernel - Re: ping //Re: [PATCH v2 0/2] squashfs: Add the mount parameter "threads="

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Message-ID: <ab006c5e-1729-3e46-0daa-0df43a05a88b@squashfs.org.uk>
Date:   Tue, 30 Aug 2022 19:34:44 +0100
From:   Phillip Lougher <phillip@...ashfs.org.uk>
To:     Xiaoming Ni <nixiaoming@...wei.com>, linux-kernel@...r.kernel.org
Cc:     wangle6@...wei.com, yi.zhang@...wei.com, wangbing6@...wei.com,
        zhongjubin@...wei.com, chenjianguo3@...wei.com
Subject: Re: ping //Re: [PATCH v2 0/2] squashfs: Add the mount parameter
 "threads="

On 30/08/2022 19:08, Phillip Lougher wrote:
> On 30/08/2022 14:38, Xiaoming Ni wrote:
>> On 2022/8/29 7:18, Phillip Lougher wrote:

>>> As regards points 1 - 3, personally I would add a default kernel
>>> configuration option that keeps the existing behaviour, build time
>>> selectable only, no additional mount time options.  Then a
>>> kernel configuration option that allows the different decompressors
>>> to be selected at mount time, but which always builds all the
>>> decompressors.  This will avoid the silliness of point 2, and
>> Would it be better to allow flexible selection of decompression mode 
>> combinations?
> 
> I told you I don't like that (*).  I also told you I want the default 
> behaviour to be the current behaviour.
> 
> Feel free to disagree, but that isn't a good way to get your patch
> reviewed or accepted by me.
> 
> Cheers
> 
> Phillip
> 
> (*) Adding options to select the decompressor at mount time, but,
>      also allowing only 1 - 2 decompressors to be built is a waste of
>      time.  It has the effect of giving something with one hand and
>      taking it alway with the other.  Build the lot, this also
>      keeps it simple.
> 
> 

It also splatters super.c with #ifdef CONFIG lines.

phillip@...enix:/external/stripe/linux/fs/squashfs$ grep "CONFIG_" super.c
#ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU
#ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU
#ifdef CONFIG_SQUASHFS_DECOMP_DEFAULT_SINGLE
#elif defined(CONFIG_SQUASHFS_DECOMP_DEFAULT_MULTI)
#elif defined(CONFIG_SQUASHFS_DECOMP_DEFAULT_PERCPU)

Or

static int squashfs_parse_param_threads(const char *str, struct 
squashfs_mount_opts *opts)
{
         unsigned long num;
         int ret;
#ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
         if (strcmp(str, "single") == 0) {
                 opts->thread_ops = &squashfs_decompressor_single;
                 return 0;
         }
#endif
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI
         if (strcmp(str, "multi") == 0) {
                 opts->thread_ops = &squashfs_decompressor_multi;
                 return 0;
         }
#endif
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU
         if (strcmp(str, "percpu") == 0) {
                 opts->thread_ops = &squashfs_decompressor_percpu;
                 return 0;
         }
#endif
         ret = kstrtoul(str, 0, &num);
         if (ret != 0 || num == 0)
                 return -EINVAL;
#ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
         if (num == 1) {
                 opts->thread_ops = &squashfs_decompressor_single;
                 return 0;
         }
#endif
#ifdef CONFIG_SQUASHFS_DECOMP_MULTI
         opts->thread_ops = &squashfs_decompressor_multi;
         if (num > opts->thread_ops->max_decompressors())
                 num = opts->thread_ops->max_decompressors();
         opts->thread_num = (int)num;
         return 0;
#else
         return -EINVAL;
#endif
}

SNIP

static int squashfs_show_options(struct seq_file *s, struct dentry *root)
{
         struct super_block *sb = root->d_sb;
         struct squashfs_sb_info *msblk = sb->s_fs_info;

         if (msblk->panic_on_errors)
                 seq_puts(s, ",errors=panic");
         else
                 seq_puts(s, ",errors=continue");

#ifdef CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU
         /*
          * thread=percpu and thread=<number> have different 
configuration effects.
          * the parameters need to be treated differently when they are 
displayed.
          */
         if (msblk->thread_ops == &squashfs_decompressor_percpu) {
                 seq_puts(s, ",threads=percpu");
                 return 0;
         }
#endif
         seq_printf(s, ",threads=%u", msblk->max_thread_num);
         return 0;
}

static int squashfs_init_fs_context(struct fs_context *fc)
{
         struct squashfs_mount_opts *opts;

         opts = kzalloc(sizeof(*opts), GFP_KERNEL);
         if (!opts)
                 return -ENOMEM;

#ifdef CONFIG_SQUASHFS_DECOMP_DEFAULT_SINGLE
         opts->thread_ops = &squashfs_decompressor_single;
#elif defined(CONFIG_SQUASHFS_DECOMP_DEFAULT_MULTI)
         opts->thread_ops = &squashfs_decompressor_multi,
#elif defined(CONFIG_SQUASHFS_DECOMP_DEFAULT_PERCPU)
         opts->thread_ops = &squashfs_decompressor_percpu;
#endif