linux-kernel - RE: [PATCH RESEND v6 1/9] pagemap: Introduce ->memory

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Date:   Tue, 17 Aug 2021 01:44:26 +0000
From:   "ruansy.fnst@...itsu.com" <ruansy.fnst@...itsu.com>
To:     Jane Chu <jane.chu@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "dm-devel@...hat.com" <dm-devel@...hat.com>
CC:     "djwong@...nel.org" <djwong@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "david@...morbit.com" <david@...morbit.com>,
        "hch@....de" <hch@....de>, "agk@...hat.com" <agk@...hat.com>,
        "snitzer@...hat.com" <snitzer@...hat.com>
Subject: RE: [PATCH RESEND v6 1/9] pagemap: Introduce ->memory_failure()

> -----Original Message-----
> From: Jane Chu <jane.chu@...cle.com>
> Subject: Re: [PATCH RESEND v6 1/9] pagemap: Introduce ->memory_failure()
> 
> Hi, ShiYang,
> 
> So I applied the v6 patch series to my 5.14-rc3 as it's what you indicated is what
> v6 was based at, and injected a hardware poison.
> 
> I'm seeing the same problem that was reported a while ago after the poison
> was consumed - in the SIGBUS payload, the si_addr is missing:
> 
> ** SIGBUS(7): canjmp=1, whichstep=0, **
> ** si_addr(0x(nil)), si_lsb(0xC), si_code(0x4, BUS_MCEERR_AR) **
> 
> The si_addr ought to be 0x7f6568000000 - the vaddr of the first page in this
> case.
> 
> Something is not right...

Hi Jane,

Sorry for late reply.  Thanks for testing.  This address should have been reported in my code. I'll check why it's finally nil.


--
Thanks.
Ruan.

> 
> thanks,
> -jane
> 
> 
> On 8/5/2021 6:17 PM, Jane Chu wrote:
> > The filesystem part of the pmem failure handling is at minimum built
> > on PAGE_SIZE granularity - an inheritance from general memory_failure
> > handling.  However, with Intel's DCPMEM technology, the error blast
> > radius is no more than 256bytes, and might get smaller with future
> > hardware generation, also advanced atomic 64B write to clear the poison.
> > But I don't see any of that could be incorporated in, given that the
> > filesystem is notified a corruption with pfn, rather than an exact
> > address.
> >
> > So I guess this question is also for Dan: how to avoid unnecessarily
> > repairing a PMD range for a 256B corrupt range going forward?
> >
> > thanks,
> > -jane
> >
> >
> > On 7/30/2021 3:01 AM, Shiyang Ruan wrote:
> >> When memory-failure occurs, we call this function which is
> >> implemented by each kind of devices.  For the fsdax case, pmem device
> >> driver implements it.  Pmem device driver will find out the
> >> filesystem in which the corrupted page located in.  And finally call
> >> filesystem handler to deal with this error.
> >>
> >> The filesystem will try to recover the corrupted data if necessary.
> >