linux-kernel - Re: [RFC PATCH 08/11] mm/damon/sysfs-schemes: implement scheme filters

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Message-Id: <20221130192636.116555-1-sj@kernel.org>
Date:   Wed, 30 Nov 2022 19:26:36 +0000
From:   SeongJae Park <sj@...nel.org>
To:     SeongJae Park <sj@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, damon@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 08/11] mm/damon/sysfs-schemes: implement scheme filters

On Thu, 24 Nov 2022 21:21:11 +0000 SeongJae Park <sj@...nel.org> wrote:

> Implement scheme filters functionality of DAMON sysfs interface by
> making the code reads the values of files under the filter directories
> and pass that to DAMON using DAMON kernel API.
> 
> Signed-off-by: SeongJae Park <sj@...nel.org>
> ---
>  mm/damon/sysfs-schemes.c | 85 +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 84 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> index 7f2bab617156..6f014b328e6f 100644
> --- a/mm/damon/sysfs-schemes.c
> +++ b/mm/damon/sysfs-schemes.c
[...]
> +static int damon_sysfs_memcg_path_to_id(char *memcg_path, unsigned short *id)
> +{
> +	struct mem_cgroup *memcg;
> +	char *path;
> +
> +	if (!memcg_path)
> +		return -EINVAL;
> +
> +	path = kmalloc(sizeof(*path) * PATH_MAX, GFP_KERNEL);
> +	if (!path)
> +		return -ENOMEM;
> +
> +	for (memcg = mem_cgroup_iter(NULL, NULL, NULL); memcg;
> +			memcg = mem_cgroup_iter(NULL, memcg, NULL)) {
> +		if (damon_sysfs_memcg_path_eq(memcg, path, memcg_path)) {
> +			*id = mem_cgroup_id(memcg);

Forgot mentioning this.  Removed memcgs can still be iterated, so this can
result in getting id of already removed cgroup.  If the user input is valid but
there is a removed memcg that has same path, this could be confused.

Removed memcg would have id 0.  The next version of this will handle the case.


Thanks,
SJ

> +			break;
> +		}
> +	}
> +
> +	kfree(path);
> +	return 0;
> +}