Re: [PATCH v6 1/3] mm: add new api to enable ksm per process

On Tue, Apr 11, 2023 at 08:16:46PM -0700, Stefan Roesch wrote:

case PR_SET_VMA: error = prctl_set_vma(arg2, arg3, arg4, arg5); break; +#ifdef CONFIG_KSM

• case PR_SET_MEMORY_MERGE:

• if (mmap_write_lock_killable(me->mm))
  

• 	return -EINTR;
  

• if (arg2) {
  

• 	int err = ksm_add_mm(me->mm);
  

• 	if (!err)
  

• 		ksm_add_vmas(me->mm);
  

in the last version of this patch, you reported the error. Now you swallow the error. I have no idea which is correct, but you've changed the behaviour without explaining it, so I assume it's wrong.

• } else {
  

• 	clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
  

• }
  

• mmap_write_unlock(me->mm);
  

• break;
  

• case PR_GET_MEMORY_MERGE:

• if (arg2 || arg3 || arg4 || arg5)
  

• 	return -EINVAL;
  

• error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
  

• break;
  

Why do we need a GET? Just for symmetry, or is there an actual need for it?