linux-kernel - Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

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Date:   Wed, 31 Mar 2021 18:56:37 +0800
From:   Aili Yao <yaoaili@...gsoft.com>
To:     Oscar Salvador <osalvador@...e.de>,
        "HORIGUCHI NAOYA堀口　直也)" 
        <naoya.horiguchi@....com>, "david@...hat.com" <david@...hat.com>
CC:     "tony.luck@...el.com" <tony.luck@...el.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "inux-edac@...r.kernel.org" <inux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "yangfeng1@...gsoft.com" <yangfeng1@...gsoft.com>,
        <yaoaili@...gsoft.com>
Subject: Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

On Thu, 25 Feb 2021 12:39:30 +0100
Oscar Salvador <osalvador@...e.de> wrote:

> On Thu, Feb 25, 2021 at 11:28:18AM +0000, HORIGUCHI NAOYA(堀口 直也) wrote:
> > Hi Aili,
> > 
> > I agree that this set_mce_nospec() is not expected to be called for
> > "already hwpoisoned" page because in the reported case the error
> > page is already contained and no need to resort changing cache mode.  
> 
> Out of curiosity, what is the current behavour now?
> Say we have an ongoing MCE which has marked the page as HWPoison but
> memory_failure did not take any action on the page yet.
> And then, we have another MCE, which ends up there.
> set_mce_nospec might clear _PAGE_PRESENT bit.
> 
> Does that have any impact on the first MCE?
> 
> > It seems to me that memory_failure() does not return MF_XXX.  But yes,
> > returning some positive value for the reported case could be a solution.  
> 
> No, you are right. I somehow managed to confuse myself.
> I see now that MF_XXX return codes are filtered out in page_action.
> 
> > We could use some negative value (error code) to report the reported case,
> > then as you mentioned above, some callers need change to handle the
> > new case, and the same is true if you use some positive value.
> > My preference is -EHWPOISON, but other options are fine if justified well.  
> 
> -EHWPOISON seems like a good fit.
> 

Hi Oscar, david:

Long away fron this topic, but i noticed today I made a stupid mistake that EHWPOISON is already
been declared, so we should better return EHWPOISON for this case.

Really sorry for this!

As the patch is still under review, I will post a new version for this, if I change this, may I add
your review tag here please?

-- 
Thanks!
Aili Yao