[dm-devel] [PATCH] dm-writecache: change config parameters using messages

[Maged Mokhtar]

Gentle ping please.

It could add flexibility in changing cache parameters after device creation.

On 22/09/2019 21:39, Maged Mokhtar wrote:
> Support changing configuration parameters using device-mapper messages
> E.g.
>    dmsetup message vg1/lv1 0 high_watermark 60
>
> Signed-off-by: Maged Mokhtar <mmokhtar at petasan.org>
> ---
>  drivers/md/dm-writecache.c |   68 +++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
>
> --- a/drivers/md/dm-writecache.c    2019-08-25 16:13:54.000000000 +0200
> +++ b/drivers/md/dm-writecache.c    2019-09-21 16:22:23.000000000 +0200
> @@ -1009,6 +1009,69 @@ static int process_flush_on_suspend_mesg
>      return 0;
>  }
>
> +static int set_config_value(struct dm_writecache *wc, char *key, char 
> *val)
> +{
> +    unsigned v,x;
> +    if (sscanf(val, "%u", &v) != 1)
> +        return -EINVAL;
> +    if (!strcasecmp(key, "high_watermark")) {
> +        if (v < 0 || v > 100)
> +            return -EINVAL;
> +        wc_lock(wc);
> +        x = (uint64_t)wc->n_blocks * (100 - v);
> +        x += 50;
> +        do_div(x, 100);
> +        if (wc->freelist_low_watermark < x) {
> +            wc_unlock(wc);
> +            return -EINVAL;
> +        }
> +        wc->freelist_high_watermark = x;
> +        wc->high_wm_percent_set = true;
> +        if (wc->freelist_size + wc->writeback_size
> +            <= wc->freelist_high_watermark)
> +            queue_work(wc->writeback_wq, &wc->writeback_work);
> +        wc_unlock(wc);
> +    }
> +    else if (!strcasecmp(key, "low_watermark")) {
> +        if (v < 0 || v > 100)
> +            return -EINVAL;
> +        wc_lock(wc);
> +        x = (uint64_t)wc->n_blocks * (100 - v);
> +        x += 50;
> +        do_div(x, 100);
> +        if (x < wc->freelist_high_watermark) {
> +            wc_unlock(wc);
> +            return -EINVAL;
> +        }
> +        wc->freelist_low_watermark = x;
> +        wc->low_wm_percent_set = true;
> +        wc_unlock(wc);
> +    }
> +    else if (!strcasecmp(key, "writeback_jobs")) {
> +        wc_lock(wc);
> +        wc->max_writeback_jobs = v;
> +        wc->max_writeback_jobs_set = true;
> +        wc_unlock(wc);
> +    }
> +    else if (!strcasecmp(key, "autocommit_blocks")) {
> +        wc_lock(wc);
> +        wc->autocommit_blocks = v;
> +        wc->autocommit_blocks_set = true;
> +        wc_unlock(wc);
> +    }
> +    else if (!strcasecmp(key, "autocommit_time")) {
> +        if (v < 1 || v > 3600000)
> +            return -EINVAL;
> +        wc_lock(wc);
> +        wc->autocommit_jiffies = msecs_to_jiffies(v);
> +        wc->autocommit_time_set = true;
> +        wc_unlock(wc);
> +    }
> +    else
> +        return -EINVAL;
> +    return 0;
> +}
> +
>  static int writecache_message(struct dm_target *ti, unsigned argc, 
> char **argv,
>                    char *result, unsigned maxlen)
>  {
> @@ -1019,6 +1082,11 @@ static int writecache_message(struct dm_
>          r = process_flush_mesg(argc, argv, wc);
>      else if (!strcasecmp(argv[0], "flush_on_suspend"))
>          r = process_flush_on_suspend_mesg(argc, argv, wc);
> +    else if (argc==2) {
> +        r = set_config_value(wc, argv[0], argv[1]);
> +        if (r==-EINVAL)
> +            DMERR("invalid message received: %s %s", argv[0], argv[1]);
> +    }
>      else
>          DMERR("unrecognised message received: %s", argv[0]);
>