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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
	linux-block@vger.kernel.org, "Christoph Hellwig" <hch@lst.de>,
	"Michal Koutný" <mkoutny@suse.com>,
	"Dan Schatzberg" <schatzberg.dan@gmail.com>
Subject: Re: [PATCH 1/6] loop: clean up blkcg association
Date: Tue, 6 Jul 2021 07:51:09 +0200	[thread overview]
Message-ID: <20210706055109.GF17027@lst.de> (raw)
In-Reply-To: <20210705102607.127810-2-ming.lei@redhat.com>

Did I mention that all this loop blkcg integration is complete and utter
garbage and should have never been merged?


>  	struct list_head *cmd_list;
> +	struct cgroup_subsys_state *blkcg_css = NULL;
> +#ifdef CONFIG_BLK_CGROUP
> +	struct request *rq = blk_mq_rq_from_pdu(cmd);
> +
> +	if (rq->bio && rq->bio->bi_blkg)
> +		blkcg_css = &bio_blkcg(rq->bio)->css;
> +#endif

This kind of junk has no business in a driver.  The blkcg code
need to provide a helper for retreiving the blkcg_css from a request,
including a stub for the the !CONFIG_BLK_CGROUP case.

>  		cur_worker = container_of(*node, struct loop_worker, rb_node);
> -		if (cur_worker->blkcg_css == cmd->blkcg_css) {
> +		if (cur_worker->blkcg_css == blkcg_css) {
>  			worker = cur_worker;
>  			break;
> -		} else if ((long)cur_worker->blkcg_css < (long)cmd->blkcg_css) {
> +		} else if ((long)cur_worker->blkcg_css < (long)blkcg_css) {

No need for an else after a break.  And more importantly no need to cast
a pointer to compare it to another pointer of the same type.

> +	struct mem_cgroup *old_memcg = NULL;
> +	struct cgroup_subsys_state *memcg_css = NULL;
> +
> +	kthread_associate_blkcg(worker->blkcg_css);
> +#ifdef CONFIG_MEMCG
> +	memcg_css = cgroup_get_e_css(worker->blkcg_css->cgroup,
> +			&memory_cgrp_subsys);
> +#endif
> +	if (memcg_css)
> +		old_memcg = set_active_memcg(
> +				mem_cgroup_from_css(memcg_css));
> +

This kind of crap also has absolutely no business in a block driver
and the memcg code should provide a proper helper.

  reply	other threads:[~2021-07-06  5:51 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-05 10:26 [PATCH 0/6] loop: cleanup charging io to mem/blkcg Ming Lei
2021-07-05 10:26 ` [PATCH 1/6] loop: clean up blkcg association Ming Lei
2021-07-06  5:51   ` Christoph Hellwig [this message]
2021-07-08  7:20     ` Ming Lei
2021-07-05 10:26 ` [PATCH 2/6] loop: conver timer for monitoring idle worker into dwork Ming Lei
2021-07-06  5:52   ` Christoph Hellwig
2021-07-08  7:23     ` Ming Lei
2021-07-05 10:26 ` [PATCH 3/6] loop: add __loop_free_idle_workers() for covering freeing workers in clearing FD Ming Lei
2021-07-05 10:26 ` [PATCH 4/6] loop: improve loop_process_work Ming Lei
2021-07-06  5:54   ` Christoph Hellwig
2021-07-05 10:26 ` [PATCH 5/6] loop: use xarray to store workers Ming Lei
2021-07-05 10:26 ` [PATCH 6/6] loop: don't add worker into idle list Ming Lei
2021-07-06 13:55   ` Dan Schatzberg
2021-07-07  3:19     ` Ming Lei
2021-07-07 13:55       ` Dan Schatzberg
2021-07-08  6:58         ` Ming Lei
2021-07-08 14:16           ` Dan Schatzberg
2021-07-08 15:01             ` Ming Lei
2021-07-08 15:15               ` Dan Schatzberg
2021-07-09  0:49                 ` Ming Lei
2021-07-09 13:47                   ` Dan Schatzberg
2021-07-08 14:41           ` Dan Schatzberg

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