Re: [patch v3 3/5] raid5: offload stripe handle to workqueue

[NeilBrown <neilb@suse.de>]

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On Tue, 27 Aug 2013 17:50:41 +0800 Shaohua Li <shli@kernel.org> wrote:

> -static struct stripe_head *__get_priority_stripe(struct r5conf *conf)
> +static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group)
>  {
> -	struct stripe_head *sh;
> +	struct stripe_head *sh = NULL, *tmp;
> +	struct list_head *handle_list = NULL;
> +
> +	if (conf->worker_cnt_per_group == 0) {
> +		handle_list = &conf->handle_list;
> +		if (list_empty(handle_list))
> +			handle_list = NULL;
> +	} else if (group != ANY_GROUP) {
> +		handle_list = &conf->worker_groups[group].handle_list;
> +		if (list_empty(handle_list))
> +			handle_list = NULL;
> +	} else {
> +		int i;
> +		for (i = 0; i < conf->group_cnt; i++) {
> +			handle_list = &conf->worker_groups[i].handle_list;
> +			if (!list_empty(handle_list))
> +				break;
> +		}
> +		if (i == conf->group_cnt)
> +			handle_list = NULL;
> +	}

Sorry, I meant to mention this last time...

The setting of handle_list to NULL seems unnecessary.  It is sufficient to
test if it is empty.
The only interesting case is the last 'else' above.  That is only reached if
worker_cnt_per_group != 0 so handle_list will get set to some list_head.
If all list_heads are empty, handle_list will be set to the last list_head
so a list_empty(handle_list) test is perfectly safe.

Also with the current code:
>  
>  	pr_debug("%s: handle: %s hold: %s full_writes: %d bypass_count: %d\n",
>  		  __func__,
> -		  list_empty(&conf->handle_list) ? "empty" : "busy",
> +		  list_empty(handle_list) ? "empty" : "busy",
                  ^^^^^^^^^^^^^^^^^^^^^^^
This will crash.


Could you fix that up please?
Thanks.
NeilBrown

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