Re: [PATCH 08/20] blkio: Add support for dynamic creation of cfq_groups

[Jeff Moyer]

Vivek Goyal <vgoyal@xxxxxxxxxx> writes:

> +	/* Do we need to take this reference */
> +	if (!css_tryget(&blkcg->css))
> +		return NULL;;

Interesting question.  It seems like, so long as you want to reference
that cgroup, you need a reference on it.  ->alloc will only give you
one, so as long as we have pointers to these squirreled away, we need to
bump the reference count.  Please take a look at this before your next
posting.

> +
> +	cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
> +	if (cfqg || !create)
> +		goto done;
> +
> +	cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC |  __GFP_ZERO,
> +					cfqd->queue->node);
Do you really have to OR in __GFP_ZERO for kzalloc?

> +	cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
> +	if (!cfqg && create)
> +		cfqg = &cfqd->root_group;

Hmm, is that really the behaviour you want?

Cheers,
Jeff
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