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

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Message-ID: <20210308223839.GA21886@hori.linux.bs1.fc.nec.co.jp>
Date:   Mon, 8 Mar 2021 22:38:39 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     "Luck, Tony" <tony.luck@...el.com>
CC:     Aili Yao <yaoaili@...gsoft.com>,
        Oscar Salvador <osalvador@...e.de>,
        "david@...hat.com" <david@...hat.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>,
        "linux-edac@...r.kernel.org" <linux-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>
Subject: Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

On Mon, Mar 08, 2021 at 06:54:02PM +0000, Luck, Tony wrote:
> >> So it should be safe to grab and hold a mutex.  See patch below.
> >
> > The mutex approach looks simpler and safer, so I'm fine with it.
> 
> Thanks.  Is that an "Acked-by:"?

Not yet, I intended to add it after full patch is submitted
(with your Signed-off-by and commit log).

> 
> >>  /**
> >>   * memory_failure - Handle memory failure of a page.
> >>   * @pfn: Page Number of the corrupted page
> >> @@ -1424,12 +1426,18 @@ int memory_failure(unsigned long pfn, int flags)
> >>  		return -ENXIO;
> >>  	}
> >>  
> >> +	mutex_lock(&mf_mutex);
> >
> > Is it better to take mutex before memory_failure_dev_pagemap() block?
> > Or we don't have to protect against race for device memory?
> 
> No races (recovery is only attempted for errors in normal memory).

OK, thanks.

- Naoya