Re: [PATCH v7 01/15] cgroup/misc: Add per resource callbacks for CSS events
From: Haitao Huang
Date: Tue Jan 23 2024 - 11:19:36 EST
On Mon, 22 Jan 2024 14:14:01 -0600, Jarkko Sakkinen <jarkko@xxxxxxxxxx>
wrote:
On Mon Jan 22, 2024 at 7:20 PM EET, Haitao Huang wrote:
From: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
The misc cgroup controller (subsystem) currently does not perform
resource type specific action for Cgroups Subsystem State (CSS) events:
the 'css_alloc' event when a cgroup is created and the 'css_free' event
when a cgroup is destroyed.
Define callbacks for those events and allow resource providers to
register the callbacks per resource type as needed. This will be
utilized later by the EPC misc cgroup support implemented in the SGX
driver.
Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
Co-developed-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
---
V7:
- Make ops one per resource type and store them in array (Michal)
- Rename the ops struct to misc_res_ops, and enforce the constraints of
required callback
functions (Jarkko)
- Moved addition of priv field to patch 4 where it was used first.
(Jarkko)
V6:
- Create ops struct for per resource callbacks (Jarkko)
- Drop max_write callback (Dave, Michal)
- Style fixes (Kai)
---
include/linux/misc_cgroup.h | 11 +++++++
kernel/cgroup/misc.c | 60 +++++++++++++++++++++++++++++++++++--
2 files changed, 68 insertions(+), 3 deletions(-)
diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index e799b1f8d05b..0806d4436208 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -27,6 +27,16 @@ struct misc_cg;
#include <linux/cgroup.h>
+/**
+ * struct misc_res_ops: per resource type callback ops.
+ * @alloc: invoked for resource specific initialization when cgroup is
allocated.
+ * @free: invoked for resource specific cleanup when cgroup is
deallocated.
+ */
+struct misc_res_ops {
+ int (*alloc)(struct misc_cg *cg);
+ void (*free)(struct misc_cg *cg);
+};
+
/**
* struct misc_res: Per cgroup per misc type resource
* @max: Maximum limit on the resource.
@@ -56,6 +66,7 @@ struct misc_cg {
u64 misc_cg_res_total_usage(enum misc_res_type type);
int misc_cg_set_capacity(enum misc_res_type type, u64 capacity);
+int misc_cg_set_ops(enum misc_res_type type, const struct misc_res_ops
*ops);
int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
u64 amount);
void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg, u64
amount);
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index 79a3717a5803..b8c32791334c 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -39,6 +39,9 @@ static struct misc_cg root_cg;
*/
static u64 misc_res_capacity[MISC_CG_RES_TYPES];
+/* Resource type specific operations */
+static const struct misc_res_ops *misc_res_ops[MISC_CG_RES_TYPES];
+
/**
* parent_misc() - Get the parent of the passed misc cgroup.
* @cgroup: cgroup whose parent needs to be fetched.
@@ -105,6 +108,36 @@ int misc_cg_set_capacity(enum misc_res_type type,
u64 capacity)
}
EXPORT_SYMBOL_GPL(misc_cg_set_capacity);
+/**
+ * misc_cg_set_ops() - set resource specific operations.
+ * @type: Type of the misc res.
+ * @ops: Operations for the given type.
+ *
+ * Context: Any context.
+ * Return:
+ * * %0 - Successfully registered the operations.
+ * * %-EINVAL - If @type is invalid, or the operations missing any
required callbacks.
+ */
+int misc_cg_set_ops(enum misc_res_type type, const struct misc_res_ops
*ops)
+{
+ if (!valid_type(type))
+ return -EINVAL;
+
+ if (!ops->alloc) {
+ pr_err("%s: alloc missing\n", __func__);
+ return -EINVAL;
+ }
+
+ if (!ops->free) {
+ pr_err("%s: free missing\n", __func__);
+ return -EINVAL;
+ }
+
+ misc_res_ops[type] = ops;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(misc_cg_set_ops);
+
/**
* misc_cg_cancel_charge() - Cancel the charge from the misc cgroup.
* @type: Misc res type in misc cg to cancel the charge from.
@@ -383,23 +416,37 @@ 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, *cg;
enum misc_res_type i;
- struct misc_cg *cg;
+ int ret;
if (!parent_css) {
- cg = &root_cg;
+ parent_cg = 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 (misc_res_ops[i]) {
+ ret = misc_res_ops[i]->alloc(cg);
+ if (ret)
+ goto alloc_err;
So I'd consider pattern like this to avoid repetition:
if (ret) {
__misc_cg_free(cg);
return PERR_PTR(ret);
}
and call __misc_cg_free() also in misc_cg_free().
Will change to do that.
Thanks
Haitao