Re: [PATCH 1/2] md: add raid4/5/6 journal mode API (for dm-raid use)

[Shaohua Li <shli@kernel.org>]

On Wed, Mar 22, 2017 at 05:44:22PM +0100, heinzm@redhat.com wrote:
> From: Heinz Mauelshagen <heinzm@redhat.com>
> 
> Upstream commit 2ded370373a400c20cf0c6e941e724e61582a867
> started the addition of "write-back" mode to MD (raid5-cache),
> i.e. support write-back caching on the raid journal device.
> 
> In order to allow the dm-raid target to switch between
> the available "write-through" and "write-back" modes,
> provide new r5c_journal_mode_set() API.
> 
> Use the new API in existing r5c_journal_mode_store()

Looks good to me, if this will be routed through dm tree, you can add:
Acked-by: Shaohua Li <shli@fb.com>


> Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
> ---
>  drivers/md/raid5-cache.c | 62 ++++++++++++++++++++++++++----------------------
>  drivers/md/raid5.h       | 11 +++++++++
>  2 files changed, 45 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 3f307be..218b6f3 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -53,16 +53,6 @@
>   */
>  #define R5L_POOL_SIZE	4
>  
> -/*
> - * r5c journal modes of the array: write-back or write-through.
> - * write-through mode has identical behavior as existing log only
> - * implementation.
> - */
> -enum r5c_journal_mode {
> -	R5C_JOURNAL_MODE_WRITE_THROUGH = 0,
> -	R5C_JOURNAL_MODE_WRITE_BACK = 1,
> -};
> -
>  static char *r5c_journal_mode_str[] = {"write-through",
>  				       "write-back"};
>  /*
> @@ -2327,40 +2317,56 @@ static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
>  	return ret;
>  }
>  
> -static ssize_t r5c_journal_mode_store(struct mddev *mddev,
> -				      const char *page, size_t length)
> +/*
> + * Set journal cache mode on @mddev (external API initially needed by dm-raid).
> + *
> + * @mode as defined in 'enum r5c_journal_mode'.
> + *
> + */
> +int r5c_journal_mode_set(struct mddev *mddev, int mode)
>  {
>  	struct r5conf *conf = mddev->private;
>  	struct r5l_log *log = conf->log;
> -	int val = -1, i;
> -	int len = length;
>  
>  	if (!log)
>  		return -ENODEV;
>  
> -	if (len && page[len - 1] == '\n')
> -		len -= 1;
> -	for (i = 0; i < ARRAY_SIZE(r5c_journal_mode_str); i++)
> -		if (strlen(r5c_journal_mode_str[i]) == len &&
> -		    strncmp(page, r5c_journal_mode_str[i], len) == 0) {
> -			val = i;
> -			break;
> -		}
> -	if (val < R5C_JOURNAL_MODE_WRITE_THROUGH ||
> -	    val > R5C_JOURNAL_MODE_WRITE_BACK)
> +	if (mode < R5C_JOURNAL_MODE_WRITE_THROUGH ||
> +	    mode > R5C_JOURNAL_MODE_WRITE_BACK)
>  		return -EINVAL;
>  
>  	if (raid5_calc_degraded(conf) > 0 &&
> -	    val == R5C_JOURNAL_MODE_WRITE_BACK)
> +	    mode == R5C_JOURNAL_MODE_WRITE_BACK)
>  		return -EINVAL;
>  
>  	mddev_suspend(mddev);
> -	conf->log->r5c_journal_mode = val;
> +	conf->log->r5c_journal_mode = mode;
>  	mddev_resume(mddev);
>  
>  	pr_debug("md/raid:%s: setting r5c cache mode to %d: %s\n",
> -		 mdname(mddev), val, r5c_journal_mode_str[val]);
> -	return length;
> +		 mdname(mddev), mode, r5c_journal_mode_str[mode]);
> +	return 0;
> +}
> +EXPORT_SYMBOL(r5c_journal_mode_set);
> +
> +static ssize_t r5c_journal_mode_store(struct mddev *mddev,
> +				      const char *page, size_t length)
> +{
> +	int mode = ARRAY_SIZE(r5c_journal_mode_str);
> +	size_t len = length;
> +
> +	if (len < 2)
> +		return -EINVAL;
> +
> +	if (page[len - 1] == '\n')
> +		len--;
> +
> +	while (mode--)
> +		if (strlen(r5c_journal_mode_str[mode]) == len &&
> +		    !strncmp(page, r5c_journal_mode_str[mode], len))
> +			break;
> +
> +	return r5c_journal_mode_set(mddev, mode) ?: length;
>  }
>  
>  struct md_sysfs_entry
> diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
> index 4bb27b9..ec8ca15 100644
> --- a/drivers/md/raid5.h
> +++ b/drivers/md/raid5.h
> @@ -547,6 +547,16 @@ struct r5worker_group {
>  	int stripes_cnt;
>  };
>  
> +/*
> + * r5c journal modes of the array: write-back or write-through.
> + * write-through mode has identical behavior as existing log only
> + * implementation.
> + */
> +enum r5c_journal_mode {
> +	R5C_JOURNAL_MODE_WRITE_THROUGH = 0,
> +	R5C_JOURNAL_MODE_WRITE_BACK = 1,
> +};
> +
>  enum r5_cache_state {
>  	R5_INACTIVE_BLOCKED,	/* release of inactive stripes blocked,
>  				 * waiting for 25% to be free
> @@ -795,4 +805,5 @@ extern void r5c_check_cached_full_stripe(struct r5conf *conf);
>  extern struct md_sysfs_entry r5c_journal_mode;
>  extern void r5c_update_on_rdev_error(struct mddev *mddev);
>  extern bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect);
> +extern int r5c_journal_mode_set(struct mddev *mddev, int journal_mode);
>  #endif
> -- 
> 2.9.3
> 
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