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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Hillf Danton <hdanton@sina.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	syzbot <syzbot+c48f34012b06c4ac67dd@syzkaller.appspotmail.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	syzkaller-bugs@googlegroups.com,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Jens Axboe <axboe@kernel.dk>,
	Markus Elfring <Markus.Elfring@web.de>
Subject: Re: kernel BUG at include/linux/swapops.h:LINE!
Date: Fri, 24 Jul 2020 14:13:11 +0300	[thread overview]
Message-ID: <20200724111311.rcjqigtjqpkenxg6@box> (raw)
In-Reply-To: <20200723073744.5268-1-hdanton@sina.com>

On Thu, Jul 23, 2020 at 03:37:44PM +0800, Hillf Danton wrote:
> 
> On Tue, 21 Jul 2020 14:11:31 +0300 Kirill A. Shutemov wrote:
> > On Mon, Jul 20, 2020 at 04:51:44PM -0700, Andrew Morton wrote:
> > > On Sun, 19 Jul 2020 14:10:19 -0700 syzbot wrote:
> > > 
> > > > syzbot has found a reproducer for the following issue on:
> > > > 
> > > > HEAD commit:    4c43049f Add linux-next specific files for 20200716
> > > > git tree:       linux-next
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12c56087100000
> > > > kernel config:  https://syzkaller.appspot.com/x/.config?x=2c76d72659687242
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=c48f34012b06c4ac67dd
> > > > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1344abeb100000
> > > > 
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by: syzbot+c48f34012b06c4ac67dd@syzkaller.appspotmail.com
> > > 
> > > Thanks.
> > > 
> > > __handle_mm_fault
> > >   ->pmd_migration_entry_wait
> > >     ->migration_entry_to_page
> > > 
> > > stumbled onto an unlocked page.
> > > 
> > > I don't immediately see a cause.  Perhaps Matthew's "THP prep patches",
> > > perhaps something else.
> > > 
> > > Is it possible to perform a bisection?
> > 
> > Maybe it's related to the new lock_page_async()?
> 
> Or is there likely the window that after copy_huge_pmd() the src pmd migrate
> entry is removed and the page unlocked but the dst is not?

No.

copy_huge_pmd() runs with exclusive mmap_lock on the source side and
destination side is not running yet.

-- 
 Kirill A. Shutemov


  reply	other threads:[~2020-07-24 11:13 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-30 17:05 kernel BUG at include/linux/swapops.h:LINE! syzbot
2020-07-19 21:10 ` syzbot
2020-07-20 23:51   ` Andrew Morton
2020-07-21  0:21     ` Matthew Wilcox
2020-07-21  2:14       ` Matthew Wilcox
2020-07-21 11:11     ` Kirill A. Shutemov
2020-07-21 15:11       ` Jens Axboe
2020-07-23  7:37       ` Hillf Danton
2020-07-24 11:13         ` Kirill A. Shutemov [this message]
2020-07-26 16:49           ` Matthew Wilcox
2020-07-27 10:31             ` Kirill A. Shutemov
2020-07-27 12:03               ` Matthew Wilcox
2020-07-27 12:59                 ` Hillf Danton
2020-07-27 13:44                   ` Matthew Wilcox
2020-07-27 14:46                     ` Hillf Danton
2020-07-29 19:21                 ` Kirill A. Shutemov
2020-07-29 19:54                   ` Matthew Wilcox
2020-07-29 22:11                     ` Matthew Wilcox
2021-05-08 11:24 ` [syzbot] " syzbot

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