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

[Phillip Lougher]

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@phoenix:/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