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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Jan Stancek <jstancek@redhat.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"ltp@lists.linux.it" <ltp@lists.linux.it>
Subject: Re: Is MADV_HWPOISON supposed to work only on faulted-in pages?
Date: Thu, 23 Feb 2017 03:23:49 +0000	[thread overview]
Message-ID: <20170223032342.GA18740@hori1.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20170220050016.GA15533@hori1.linux.bs1.fc.nec.co.jp>

On Mon, Feb 20, 2017 at 05:00:17AM +0000, Horiguchi Naoya(堀口 直也) wrote:
> On Tue, Feb 14, 2017 at 04:41:29PM +0100, Jan Stancek wrote:
> > Hi,
> >
> > code below (and LTP madvise07 [1]) doesn't produce SIGBUS,
> > unless I touch/prefault page before call to madvise().
> >
> > Is this expected behavior?
> 
> Thank you for reporting.
> 
> madvise(MADV_HWPOISON) triggers page fault when called on the address
> over which no page is faulted-in, so I think that SIGBUS should be
> called in such case.
> 
> But it seems that memory error handler considers such a page as "reserved
> kernel page" and recovery action fails (see below.)
> 
>   [  383.371372] Injecting memory failure for page 0x1f10 at 0x7efcdc569000
>   [  383.375678] Memory failure: 0x1f10: reserved kernel page still referenced by 1 users
>   [  383.377570] Memory failure: 0x1f10: recovery action for reserved kernel page: Failed
> 
> I'm not sure how/when this behavior was introduced, so I try to understand.

I found that this is a zero page, which is not recoverable for memory
error now.

> IMO, the test code below looks valid to me, so no need to change.

I think that what the testcase effectively does is to test whether memory
handling on zero pages works or not.
And the testcase's failure seems acceptable, because it's simply not-implemented yet.
Maybe recovering from error on zero page is possible (because there's no data
loss for memory error,) but I'm not sure that code might be simple enough and/or
it's worth doing ...

Thanks,
Naoya Horiguchi
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WARNING: multiple messages have this Message-ID
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: ltp@lists.linux.it
Subject: [LTP] Is MADV_HWPOISON supposed to work only on faulted-in pages?
Date: Thu, 23 Feb 2017 03:23:49 +0000	[thread overview]
Message-ID: <20170223032342.GA18740@hori1.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20170220050016.GA15533@hori1.linux.bs1.fc.nec.co.jp>

On Mon, Feb 20, 2017 at 05:00:17AM +0000, Horiguchi Naoya(堀口 直也) wrote:
> On Tue, Feb 14, 2017 at 04:41:29PM +0100, Jan Stancek wrote:
> > Hi,
> >
> > code below (and LTP madvise07 [1]) doesn't produce SIGBUS,
> > unless I touch/prefault page before call to madvise().
> >
> > Is this expected behavior?
> 
> Thank you for reporting.
> 
> madvise(MADV_HWPOISON) triggers page fault when called on the address
> over which no page is faulted-in, so I think that SIGBUS should be
> called in such case.
> 
> But it seems that memory error handler considers such a page as "reserved
> kernel page" and recovery action fails (see below.)
> 
>   [  383.371372] Injecting memory failure for page 0x1f10 at 0x7efcdc569000
>   [  383.375678] Memory failure: 0x1f10: reserved kernel page still referenced by 1 users
>   [  383.377570] Memory failure: 0x1f10: recovery action for reserved kernel page: Failed
> 
> I'm not sure how/when this behavior was introduced, so I try to understand.

I found that this is a zero page, which is not recoverable for memory
error now.

> IMO, the test code below looks valid to me, so no need to change.

I think that what the testcase effectively does is to test whether memory
handling on zero pages works or not.
And the testcase's failure seems acceptable, because it's simply not-implemented yet.
Maybe recovering from error on zero page is possible (because there's no data
loss for memory error,) but I'm not sure that code might be simple enough and/or
it's worth doing ...

Thanks,
Naoya Horiguchi

  reply	other threads:[~2017-02-23  3:25 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-14 15:41 Is MADV_HWPOISON supposed to work only on faulted-in pages? Jan Stancek
2017-02-14 15:41 ` [LTP] " Jan Stancek
2017-02-20  5:00 ` Naoya Horiguchi
2017-02-20  5:00   ` [LTP] " Naoya Horiguchi
2017-02-23  3:23   ` Naoya Horiguchi [this message]
2017-02-23  3:23     ` Naoya Horiguchi
2017-02-25  2:28     ` Yisheng Xie
2017-02-25  2:28       ` [LTP] " Yisheng Xie
2017-02-27  1:20       ` Naoya Horiguchi
2017-02-27  1:20         ` [LTP] " Naoya Horiguchi
2017-02-27  4:27         ` Zi Yan
2017-02-27  4:27           ` [LTP] " Zi Yan
2017-02-27  6:33           ` Naoya Horiguchi
2017-02-27  6:33             ` [LTP] " Naoya Horiguchi
2017-02-27 16:10             ` Zi Yan
2017-02-27 16:10               ` [LTP] " Zi Yan
2017-03-14 13:20             ` Cyril Hrubis
2017-03-14 13:20               ` Cyril Hrubis
2017-03-27 12:08             ` Richard Palethorpe
2017-03-27 12:08               ` Richard Palethorpe
2017-03-27 23:54     ` Andi Kleen
2017-03-27 23:54       ` [LTP] " Andi Kleen
2017-03-28  8:25       ` Cyril Hrubis
2017-03-28  8:25         ` Cyril Hrubis
2017-03-28 20:26         ` Andi Kleen
2017-03-28 20:26           ` Andi Kleen

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