From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
"mingo@kernel.org" <mingo@kernel.org>,
"dan.j.williams@intel.com" <dan.j.williams@intel.com>,
Huang Ying <ying.huang@intel.com>,
Pavel Tatashin <pasha.tatashin@oracle.com>
Subject: Re: kernel panic in reading /proc/kpageflags when enabling RAM-simulated PMEM
Date: Wed, 6 Jun 2018 05:16:24 +0000 [thread overview]
Message-ID: <20180606051624.GA16021@hori1.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20180605073500.GA23766@hori1.linux.bs1.fc.nec.co.jp>
On Tue, Jun 05, 2018 at 07:35:01AM +0000, Horiguchi Naoya(堀口 直也) wrote:
> On Mon, Jun 04, 2018 at 06:18:36PM -0700, Matthew Wilcox wrote:
> > On Tue, Jun 05, 2018 at 12:54:03AM +0000, Naoya Horiguchi wrote:
> > > Reproduction precedure is like this:
> > > - enable RAM based PMEM (with a kernel boot parameter like memmap=1G!4G)
> > > - read /proc/kpageflags (or call tools/vm/page-types with no arguments)
> > > (- my kernel config is attached)
> > >
> > > I spent a few days on this, but didn't reach any solutions.
> > > So let me report this with some details below ...
> > >
> > > In the critial page request, stable_page_flags() is called with an argument
> > > page whose ->compound_head was somehow filled with '0xffffffffffffffff'.
> > > And compound_head() returns (struct page *)(head - 1), which explains the
> > > address 0xfffffffffffffffe in the above message.
> >
> > Hm. compound_head shares with:
> >
> > struct list_head lru;
> > struct list_head slab_list; /* uses lru */
> > struct { /* Partial pages */
> > struct page *next;
> > unsigned long _compound_pad_1; /* compound_head */
> > unsigned long _pt_pad_1; /* compound_head */
> > struct dev_pagemap *pgmap;
> > struct rcu_head rcu_head;
> >
> > None of them should be -1.
> >
> > > It seems that this kernel panic happens when reading kpageflags of pfn range
> > > [0xbffd7, 0xc0000), which coresponds to a 'reserved' range.
> > >
> > > [ 0.000000] user-defined physical RAM map:
> > > [ 0.000000] user: [mem 0x0000000000000000-0x000000000009fbff] usable
> > > [ 0.000000] user: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> > > [ 0.000000] user: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> > > [ 0.000000] user: [mem 0x0000000000100000-0x00000000bffd6fff] usable
> > > [ 0.000000] user: [mem 0x00000000bffd7000-0x00000000bfffffff] reserved
> > > [ 0.000000] user: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> > > [ 0.000000] user: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> > > [ 0.000000] user: [mem 0x0000000100000000-0x000000013fffffff] persistent (type 12)
> > >
> > > So I guess 'memmap=' parameter might badly affect the memory initialization process.
> > >
> > > This problem doesn't reproduce on v4.17, so some pre-released patch introduces it.
> > > I hope this info helps you find the solution/workaround.
> >
> > Can you try bisecting this? It could be one of my patches to reorder struct
> > page, or it could be one of Pavel's deferred page initialisation patches.
> > Or something else ;-)
>
> Thank you for the comment. I'm trying bisecting now, let you know the result later.
>
> And I found that my statement "not reproduce on v4.17" was wrong (I used
> different kvm guests, which made some different test condition and misguided me),
> this seems an older (at least < 4.15) bug.
(Cc: Pavel)
Bisection showed that the following commit introduced this issue:
commit f7f99100d8d95dbcf09e0216a143211e79418b9f
Author: Pavel Tatashin <pasha.tatashin@oracle.com>
Date: Wed Nov 15 17:36:44 2017 -0800
mm: stop zeroing memory during allocation in vmemmap
This patch postpones struct page zeroing to later stage of memory initialization.
My kernel config disabled CONFIG_DEFERRED_STRUCT_PAGE_INIT so two callsites of
__init_single_page() were never reached. So in such case, struct pages populated
by vmemmap_pte_populate() could be left uninitialized?
And I'm not sure yet how this issue becomes visible with memmap= setting.
Thanks,
Naoya Horiguchi
next prev parent reply other threads:[~2018-06-06 5:17 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-05 0:54 kernel panic in reading /proc/kpageflags when enabling RAM-simulated PMEM Naoya Horiguchi
2018-06-05 1:18 ` Matthew Wilcox
2018-06-05 7:35 ` Naoya Horiguchi
2018-06-06 5:16 ` Naoya Horiguchi [this message]
2018-06-06 8:04 ` Oscar Salvador
2018-06-06 8:53 ` Oscar Salvador
2018-06-06 9:06 ` Naoya Horiguchi
2018-06-06 9:24 ` Naoya Horiguchi
2018-06-07 6:22 ` Naoya Horiguchi
2018-06-07 6:59 ` Oscar Salvador
2018-06-07 9:49 ` Oscar Salvador
2018-06-07 10:02 ` Naoya Horiguchi
2018-06-11 9:05 ` Naoya Horiguchi
2018-06-13 5:41 ` [PATCH v1] mm: zero remaining unavailable struct pages (Re: kernel panic in reading /proc/kpageflags when enabling RAM-simulated PMEM) Naoya Horiguchi
2018-06-13 8:40 ` Oscar Salvador
2018-06-14 4:56 ` Naoya Horiguchi
2018-06-13 9:07 ` Michal Hocko
2018-06-14 5:16 ` Naoya Horiguchi
2018-06-14 5:38 ` Oscar Salvador
2018-06-14 6:34 ` [PATCH v2] x86/e820: put !E820_TYPE_RAM regions into memblock.reserved Naoya Horiguchi
2018-06-14 7:21 ` Oscar Salvador
2018-06-14 11:24 ` Oscar Salvador
2018-06-15 0:58 ` Naoya Horiguchi
2018-06-14 21:30 ` Oscar Salvador
2018-06-15 1:09 ` Naoya Horiguchi
2018-06-15 7:29 ` [PATCH v3] " Naoya Horiguchi
2018-06-15 8:41 ` Michal Hocko
2018-06-15 14:00 ` Pavel Tatashin
2018-06-15 14:10 ` Michal Hocko
2018-06-15 14:33 ` Oscar Salvador
2018-06-15 16:02 ` Pavel Tatashin
2018-06-18 23:36 ` Andrew Morton
2018-06-19 0:49 ` Pavel Tatashin
2018-07-02 20:05 ` Pavel Tatashin
2018-07-02 20:28 ` Andrew Morton
2018-07-02 20:31 ` Pavel Tatashin
2018-06-14 7:00 ` [PATCH v1] mm: zero remaining unavailable struct pages (Re: kernel panic in reading /proc/kpageflags when enabling RAM-simulated PMEM) Michal Hocko
2018-06-15 1:07 ` Naoya Horiguchi
2018-06-15 8:39 ` Michal Hocko
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