On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> From: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
>
> Consumers of the misc cgroup controller might need to perform separate
> actions for Cgroups Subsystem State(CSS) events: cgroup alloc and free.
nit: s/State(CSS)/State (CSS)/
"cgroup alloc" and "cgroup free" mean absolutely nothing.
> In addition, writes to the max value may also need separate action. Add
What "the max value"?
> the ability to allow downstream users to setup callbacks for these
> operations, and call the corresponding per-resource-type callback when
> appropriate.
Who are "the downstream users" and what sort of callbacks they setup?
>
> This code will be utilized by the SGX driver in a future patch.
>
> Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
> Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
> ---
> V4:
> - Moved this to the front of the series.
> - Applies on cgroup/for-6.6 with the overflow fix for misc.
>
> V3:
> - Removed the released() callback
> ---
> include/linux/misc_cgroup.h | 5 +++++
> kernel/cgroup/misc.c | 32 +++++++++++++++++++++++++++++---
> 2 files changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
> index e799b1f8d05b..e1bcd176c2de 100644
> --- a/include/linux/misc_cgroup.h
> +++ b/include/linux/misc_cgroup.h
> @@ -37,6 +37,11 @@ struct misc_res {
> u64 max;
> atomic64_t usage;
> atomic64_t events;
> +
> + /* per resource callback ops */
> + int (*misc_cg_alloc)(struct misc_cg *cg);
> + void (*misc_cg_free)(struct misc_cg *cg);
> + void (*misc_cg_max_write)(struct misc_cg *cg);
> };
>
> /**
> diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
> index 79a3717a5803..e0092170d0dd 100644
> --- a/kernel/cgroup/misc.c
> +++ b/kernel/cgroup/misc.c
> @@ -276,10 +276,13 @@ static ssize_t misc_cg_max_write(struct kernfs_open_file *of, char *buf,
>
> cg = css_misc(of_css(of));
>
> - if (READ_ONCE(misc_res_capacity[type]))
> + if (READ_ONCE(misc_res_capacity[type])) {
> WRITE_ONCE(cg->res[type].max, max);
> - else
> + if (cg->res[type].misc_cg_max_write)
> + cg->res[type].misc_cg_max_write(cg);
> + } else {
> ret = -EINVAL;
> + }
>
> return ret ? ret : nbytes;
> }
> @@ -383,23 +386,39 @@ static struct cftype misc_cg_files[] = {
> static struct cgroup_subsys_state *
> misc_cg_alloc(struct cgroup_subsys_state *parent_css)
> {
> + struct misc_cg *parent_cg;
> enum misc_res_type i;
> struct misc_cg *cg;
> + int ret;
>
> if (!parent_css) {
> cg = &root_cg;
> + parent_cg = &root_cg;
> } else {
> cg = kzalloc(sizeof(*cg), GFP_KERNEL);
> if (!cg)
> return ERR_PTR(-ENOMEM);
> + parent_cg = css_misc(parent_css);
> }
>
> for (i = 0; i < MISC_CG_RES_TYPES; i++) {
> WRITE_ONCE(cg->res[i].max, MAX_NUM);
> atomic64_set(&cg->res[i].usage, 0);
> + if (parent_cg->res[i].misc_cg_alloc) {
> + ret = parent_cg->res[i].misc_cg_alloc(cg);
> + if (ret)
> + goto alloc_err;
> + }
> }
>
> return &cg->css;
> +
> +alloc_err:
> + for (i = 0; i < MISC_CG_RES_TYPES; i++)
> + if (parent_cg->res[i].misc_cg_free)
> + cg->res[i].misc_cg_free(cg);
> + kfree(cg);
> + return ERR_PTR(ret);
> }
>
> /**
> @@ -410,7 +429,14 @@ misc_cg_alloc(struct cgroup_subsys_state *parent_css)
> */
> static void misc_cg_free(struct cgroup_subsys_state *css)
> {
> - kfree(css_misc(css));
> + struct misc_cg *cg = css_misc(css);
> + enum misc_res_type i;
> +
> + for (i = 0; i < MISC_CG_RES_TYPES; i++)
> + if (cg->res[i].misc_cg_free)
> + cg->res[i].misc_cg_free(cg);
> +
> + kfree(cg);
> }
>
> /* Cgroup controller callbacks */
> --
> 2.25.1
BR, Jarkko
