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

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Date:   Mon, 16 Aug 2021 10:20:05 -0700
From:   Jane Chu <jane.chu@...cle.com>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, dm-devel@...hat.com
Cc:     djwong@...nel.org, dan.j.williams@...el.com, david@...morbit.com,
        hch@....de, agk@...hat.com, snitzer@...hat.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...

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.
>