Re: [PATCH v7 09/15] x86/sgx: Charge mem_cgroup for per-cgroup reclamation

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Hi Tim,
On Fri, 02 Feb 2024 17:45:05 -0600, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> wrote:

On Mon, 2024-01-22 at 09:20 -0800, Haitao Huang wrote:

@@ -1047,29 +1037,38 @@ static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
  * @encl:	an enclave pointer
  * @page_index:	enclave page index
  * @backing:	data for accessing backing storage for the page
+ * @indirect:	in ksgxd or EPC cgroup work queue context
+ *
+ * Create a backing page for loading data back into an EPC page with ELDU. This function takes + * a reference on a new backing page which must be dropped with a corresponding call to
+ * sgx_encl_put_backing().
  *
- * When called from ksgxd, sets the active memcg from one of the
- * mms in the enclave's mm_list prior to any backing page allocation,
- * in order to ensure that shmem page allocations are charged to the
- * enclave. Create a backing page for loading data back into an EPC page with
- * ELDU.  This function takes a reference on a new backing page which
- * must be dropped with a corresponding call to sgx_encl_put_backing().
+ * When @indirect is true, sets the active memcg from one of the mms in the enclave's mm_list + * prior to any backing page allocation, in order to ensure that shmem page allocations are
+ * charged to the enclave.
  *
  * Return:
  *   0 on success,
  *   -errno otherwise.
  */
int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index,
-			   struct sgx_backing *backing)
+			   struct sgx_backing *backing, bool indirect)
 {
-	struct mem_cgroup *encl_memcg = sgx_encl_get_mem_cgroup(encl);
-	struct mem_cgroup *memcg = set_active_memcg(encl_memcg);
+	struct mem_cgroup *encl_memcg;
+	struct mem_cgroup *memcg;
 	int ret;

+	if (indirect) {
+		encl_memcg = sgx_encl_get_mem_cgroup(encl);
+		memcg = set_active_memcg(encl_memcg);
+	}
+
 	ret = __sgx_encl_get_backing(encl, page_index, backing);

-	set_active_memcg(memcg);
-	mem_cgroup_put(encl_memcg);
+	if (indirect) {
+		set_active_memcg(memcg);
+		mem_cgroup_put(encl_memcg);
+	}



You can reduce the number of if statements to make the logic
simpler.  Something like

	if (!indirect)
		return __sgx_encl_get_backing(encl, page_index, backing);

	encl_memcg = sgx_encl_get_mem_cgroup(encl);
	memcg = set_active_memcg(encl_memcg);
	ret = __sgx_encl_get_backing(encl, page_index, backing);
	set_active_memcg(memcg);
	mem_cgroup_put(encl_memcg);

 	return ret;

Tim


Yes, will do.
Thanks
Haitao




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