linux-kernel - Re: [PATCH v3 3/6] mm: shrinkers: provide shrinkers with names

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Message-ID: <20220520164115.oectf3x5hkwesioi@moria.home.lan>
Date:   Fri, 20 May 2022 12:41:15 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Dave Chinner <dchinner@...hat.com>,
        linux-kernel@...r.kernel.org, Hillf Danton <hdanton@...a.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v3 3/6] mm: shrinkers: provide shrinkers with names

On Mon, May 09, 2022 at 11:38:17AM -0700, Roman Gushchin wrote:
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index ad9f16689419..c1f734ab86b3 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -812,7 +812,7 @@ int bch_btree_cache_alloc(struct cache_set *c)
>  	c->shrink.seeks = 4;
>  	c->shrink.batch = c->btree_pages * 2;
>  
> -	if (register_shrinker(&c->shrink))
> +	if (register_shrinker(&c->shrink, "btree"))
>  		pr_warn("bcache: %s: could not register shrinker\n",
>  				__func__);

These drivers need better names for their shrinkers - there will often be
multiple instances in use on a system and we need to distinguish.

Also, "btree" isn't a good name for the bcache shrinker - "bcache-%pU",
c->set_uuid would be a good name for bcache's shrinker, it'll match up with the
cache set directory in /sys/fs/bcache/.

For others (device mapper, md, etc.) there should be a minor device number you
can reference.