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

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Date:   Thu, 5 Aug 2021 18:17:33 -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()

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.