Matthew Wilcox <willy@xxxxxxxxxxxxx> writes:
> 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.
>
I don't see how the error is swallowed in the arg2 case. If there is
an error ksm_add_vmas is not executedd and at the end of the function
the error is returned. Am I missing something?
>> + } 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?
There are three reasons:
- For symmetry
- The ksm sharing is inherited by child processes. This allows the test
programs to verify that this is working.
- For child processes it might be useful to have the ability to check if
ksm sharing has been enabled
