On Thu, Sep 30, 2021 at 4:23 AM Tkaczyk, Mariusz
<mariusz.tkaczyk@xxxxxxxxxxxxxxx> wrote:
>
> Hi Song,
> On 29.09.2021 03:29, Song Liu wrote:
> >>>>>>>
> >>>>>>>> set_bit(MD_SB_NEED_REWRITE, &mddev->sb_flags);
> >>>>>>>> set_bit(LastDev, &rdev->flags);
> >>>>>>>> }
> >>>>>>>> @@ -2979,7 +2980,8 @@ state_store(struct md_rdev *rdev, const char *buf,
> >>>>>>>> size_t len)
> >>>>>>>> int err = -EINVAL;
> >>>>>>>> if (cmd_match(buf, "faulty") && rdev->mddev->pers) {
> >>>>>>>> md_error(rdev->mddev, rdev);
> >>>>>>>> - if (test_bit(Faulty, &rdev->flags))
> >>>>>>>> +
> >>>>>>>> + if (!test_bit(MD_BROKEN, &rdev->mddev->flags))
> >>>>>>>
> >>>>>>> I don't think this makes much sense. EBUSY for already failed array
> >>>>>>> sounds weird.
> >>>>>>> Also, shall we also set MD_BROKEN here?
> >>>>>>>
> >>>>>> Actually, we just called md_error above, so we don't need to set MD_BROKEN
> >>>>>> here.
> >>>>>> But we shouldn't return EBUSY in such cases, right?
> >>>>>>
> >>>>> About EBUSY:
> >>>>> This is how it is implemented in mdadm, we are expecting it in
> >>>>> case of failure. See my fix[2].
> >>>>> I agree that it can be confusing, but this is how it is working.
> >>>>> Do you want to change it across mdadm and md?
> >>>>> This will break compatibility.
> >>>>>
> >>>>> About MD_BROKEN:
> >>>>> As you see we are determining failure by checking rdev state, if "Faulty"
> >>>>> in flags after md_error() is not set, then it assumes that array is
> >>>>> failed and EBUSY is returned to userspace.
> >>>>
> >>>> This changed the behavior for raid0, no?
> >>>>
> >>>> W/o the change mdadm --fail on raid0 will get EBUSY. W/ this change,
> >>>> it will get 0, and the device is NOT marked as faulty, right?
> >>>>
> >>> See commit mentioned in description. MD_BROKEN is used for raid0,
> >>> so EBUSY is returned, same as w/o patch.
> >
> > Hmm... I am still confused. In state_store(), md_error is a no-op for raid0,
> > which will not set Faulty or MD_BROKEN. So we will get -EBUSY w/o
> > the patch and 0 w/ the patch, no? It is probably not a serious issue though.
> >
> >
> Yeah, you are right. There is no error_handler. I missed that.
> Now, I reviewed raid0 again.
>
> With my change result won't be clear for raid0, it is correlated with IO.
> When drive disappears and there is IO, then it could return -EBUSY,
> raid0_make_request() may set MD_BROKEN first.
> In there is no IO then 0 will be returned. I need to close this gap.
> Thanks for your curiosity.
>
> So, please tell me, are you ok with idea of this patch? I will send
> requested details with v2 but I want to know if I choose good way to close
> raid5 issue, which is a main problem.
I think the idea is good. Maybe we can just add an error_hander for raid0 so
it is more consistent?
Besides that, please also add more explanations about MD_BROKEN in the
next version.
Thanks,
Song
