From: Matthew Wilcox <willy@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: linux-mm@kvack.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Hugh Dickins <hughd@google.com>
Subject: Re: File THP and HWPoison
Date: Tue, 16 Mar 2021 16:52:08 +0000 [thread overview]
Message-ID: <20210316165208.GC3420@casper.infradead.org> (raw)
In-Reply-To: <20210316163649.GR203350@tassilo.jf.intel.com>
On Tue, Mar 16, 2021 at 09:36:49AM -0700, Andi Kleen wrote:
> > So we now map the PMD-sized page into userspace, even though it has a
> > HWPoison in it.
>
> Yes that's bad. It might panic the system.
>
> >
> > I think there are two things that we should be doing:
> >
> > 1. Attempt to split THPs which are file-backed. That makes most of this
> > problem disappear because there won't be THPs with HWPoison, mostly.
>
> That seems simple and sensible.
>
> > 2. When the THP fails to split, use a spare page flag to indicate that
> > the THP contains a HWPoison bit in one of its subpages. There are a
> > lot of PF_SECOND flags available for this purpose.
>
> Why should it fail? I thought splitting always succeeds.
If somebody has a temporary reference to it, splitting will fail.
eg a process is currently doing a read() from it, so filemap_read()
has a reference on the page. This is why THPs support a delayed split
(currently used under memory pressure, but we could do something using
that delayed list to schedule the page for splitting later if it has
HWPoison).
next prev parent reply other threads:[~2021-03-16 16:52 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 14:09 Matthew Wilcox
2021-03-16 16:36 ` Andi Kleen
2021-03-16 16:52 ` Matthew Wilcox [this message]
2021-03-18 14:08 ` Kirill A. Shutemov
2021-03-18 14:57 ` Matthew Wilcox
2021-03-18 17:25 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-18 18:05 ` Yang Shi
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