From: Mike Rapoport <rppt@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Andrea Arcangeli" <aarcange@redhat.com>,
"Baoquan He" <bhe@redhat.com>, "Borislav Petkov" <bp@alien8.de>,
"Chris Wilson" <chris@chris-wilson.co.uk>,
"David Hildenbrand" <david@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Łukasz Majczak" <lma@semihalf.com>,
"Mel Gorman" <mgorman@suse.de>,
"Michal Hocko" <mhocko@kernel.org>,
"Mike Rapoport" <rppt@linux.ibm.com>, "Qian Cai" <cai@lca.pw>,
"Sarvela, Tomi P" <tomi.p.sarvela@intel.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Vlastimil Babka" <vbabka@suse.cz>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
stable@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v5 1/1] mm: refactor initialization of struct page for holes in memory layout
Date: Mon, 8 Feb 2021 23:25:26 +0200 [thread overview]
Message-ID: <20210208212526.GW242749@kernel.org> (raw)
In-Reply-To: <20210208131100.7273d249a5d00cac0d247fcf@linux-foundation.org>
On Mon, Feb 08, 2021 at 01:11:00PM -0800, Andrew Morton wrote:
> On Mon, 8 Feb 2021 13:08:20 +0200 Mike Rapoport <rppt@kernel.org> wrote:
>
> > There could be struct pages that are not backed by actual physical memory.
> > This can happen when the actual memory bank is not a multiple of
> > SECTION_SIZE or when an architecture does not register memory holes
> > reserved by the firmware as memblock.memory.
> >
> > Such pages are currently initialized using init_unavailable_mem() function
> > that iterates through PFNs in holes in memblock.memory and if there is a
> > struct page corresponding to a PFN, the fields of this page are set to
> > default values and it is marked as Reserved.
> >
> > init_unavailable_mem() does not take into account zone and node the page
> > belongs to and sets both zone and node links in struct page to zero.
> >
> > On a system that has firmware reserved holes in a zone above ZONE_DMA, for
> > instance in a configuration below:
> >
> > # grep -A1 E820 /proc/iomem
> > 7a17b000-7a216fff : Unknown E820 type
> > 7a217000-7bffffff : System RAM
> >
> > unset zone link in struct page will trigger
> >
> > VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
> >
> > because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone link
> > in struct page) in the same pageblock.
> >
> > ...
> >
> >
> > Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions rather
> > that check each PFN")
>
> What are your thoughts on the priority of this (rather large!) fix?
> Are such systems sufficiently common to warrant a 5.11 merge? -stable?
I don't know how common are such systems, but the bug is exposed only for
builds with DEBUG_VM=y, so after problems with previous versions discovered
by various CI systems I'd say to hold it off till 5.11 is out.
If this time the fix works it'll make it to -stable anyway :)
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2021-02-08 21:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 11:08 [PATCH v5 1/1] mm: refactor initialization of struct page for holes in memory layout Mike Rapoport
2021-02-08 21:11 ` Andrew Morton
2021-02-08 21:25 ` Mike Rapoport [this message]
2021-02-12 9:55 ` David Hildenbrand
2021-02-12 9:56 ` David Hildenbrand
2021-02-12 10:11 ` Michal Hocko
2021-02-12 10:16 ` David Hildenbrand
2021-02-12 10:37 ` Michal Hocko
2021-02-14 17:29 ` Mike Rapoport
2021-02-15 8:45 ` David Hildenbrand
2021-02-16 11:13 ` Mike Rapoport
2021-02-12 10:33 ` Michal Hocko
2021-02-12 10:42 ` David Hildenbrand
2021-02-12 13:18 ` Michal Hocko
2021-02-14 18:00 ` Mike Rapoport
2021-02-15 9:00 ` Michal Hocko
2021-02-15 9:05 ` David Hildenbrand
2021-02-15 21:24 ` Mike Rapoport
2021-02-16 8:33 ` Michal Hocko
2021-02-16 11:01 ` Mike Rapoport
2021-02-16 11:39 ` Michal Hocko
2021-02-16 12:34 ` Vlastimil Babka
2021-02-16 12:59 ` Vlastimil Babka
2021-02-16 13:11 ` Michal Hocko
2021-02-16 16:39 ` Vlastimil Babka
2021-02-16 17:49 ` Mike Rapoport
2021-02-17 12:27 ` Vlastimil Babka
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