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From: Dan Williams <dan.j.williams@intel.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Tony Luck <tony.luck@intel.com>, Borislav Petkov <bp@alien8.de>,
	Naoya Horiguchi <naoya.horiguchi@nec.com>,
	linux-edac@vger.kernel.org, Linux MM <linux-mm@kvack.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Jane Chu <jane.chu@oracle.com>, david <david@fromorbit.com>
Subject: Re: [RFC] Make the memory failure blast radius more precise
Date: Tue, 23 Jun 2020 14:48:12 -0700
Message-ID: <CAPcyv4jDfm10pGBJHJYA_=C0-+JMor-r7ViAJSJ=u4ZW0FqAow@mail.gmail.com> (raw)
In-Reply-To: <20200623201745.GG21350@casper.infradead.org>

On Tue, Jun 23, 2020 at 1:18 PM Matthew Wilcox <willy@infradead.org> wrote:
>
>
> Hardware actually tells us the blast radius of the error, but we ignore
> it and take out the entire page.  We've had a customer request to know
> exactly how much of the page is damaged so they can avoid reconstructing
> an entire 2MB page if only a single cacheline is damaged.
>
> This is only a strawman that I did in an hour or two; I'd appreciate
> architectural-level feedback.  Should I just convert memory_failure() to
> always take an address & granularity?  Should I create a struct to pass
> around (page, phys, granularity) instead of reconstructing the missing
> pieces in half a dozen functions?  Is this functionality welcome at all,
> or is the risk of upsetting applications which expect at least a page
> of granularity too high?
>
> I can see places where I've specified a plain PAGE_SHIFT insted of
> interrogating a compound page for its size.  I'd probably split this
> patch up into two or three pieces for applying.
>
> I've also blindly taken out the call to unmap_mapping_range().  Again,
> the customer requested that we not do this.  That deserves to be in its
> own patch and properly justified.

I had been thinking that we could not do much with the legacy
memory-failure reporting model and that applications that want a new
model would need to opt-into it. This topic also dovetails with what
Dave and I had been discussing in terms coordinating memory error
handling with the filesystem which may have more information about
multiple mappings of a DAX page (reflink) [1].

[1]: http://lore.kernel.org/r/20200311063942.GE10776@dread.disaster.area

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 20:17 Matthew Wilcox
2020-06-23 21:48 ` Dan Williams [this message]
2020-06-23 22:04 ` Luck, Tony
2020-06-23 22:17   ` Matthew Wilcox
2020-06-23 22:26     ` Luck, Tony
2020-06-23 22:40       ` Matthew Wilcox
2020-06-24  0:01         ` Darrick J. Wong
2020-06-24 12:10           ` Matthew Wilcox
2020-06-24 23:21             ` Dan Williams
2020-06-25  0:17               ` Matthew Wilcox
2020-06-25  1:18                 ` Dan Williams
2020-06-24 21:22         ` Jane Chu
2020-06-25  0:13           ` Luck, Tony
2020-06-25 16:23             ` Jane Chu
2020-06-24  4:32   ` David Rientjes
2020-06-24 20:57     ` Jane Chu
2020-06-24 22:01       ` David Rientjes
2020-06-25  2:16     ` HORIGUCHI NAOYA(堀口 直也)

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