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

[Haitao Huang]

Hi Tim,
On Fri, 02 Feb 2024 17:45:05 -0600, Tim Chen <tim.c.c...@linux.intel.com>  
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