linux-kernel - Re: linux-next test error

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Date:   Wed, 5 Sep 2018 11:53:26 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Souptick Joarder <jrdr.linux@...il.com>
Cc:     Jan Kara <jack@...e.cz>,
        syzbot <syzbot+87a05ae4accd500f5242@...kaller.appspotmail.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        tim.c.chen@...ux.intel.com, zwisler@...nel.org
Subject: Re: linux-next test error

On Wed, Sep 5, 2018 at 11:50 AM, Souptick Joarder <jrdr.linux@...il.com> wrote:
> On Wed, Sep 5, 2018 at 2:25 PM Jan Kara <jack@...e.cz> wrote:
>>
>> On Wed 05-09-18 00:13:02, syzbot wrote:
>> > Hello,
>> >
>> > syzbot found the following crash on:
>> >
>> > HEAD commit:    387ac6229ecf Add linux-next specific files for 20180905
>> > git tree:       linux-next
>> > console output: https://syzkaller.appspot.com/x/log.txt?x=149c67a6400000
>> > kernel config:  https://syzkaller.appspot.com/x/.config?x=ad5163873ecfbc32
>> > dashboard link: https://syzkaller.appspot.com/bug?extid=87a05ae4accd500f5242
>> > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> >
>> > Unfortunately, I don't have any reproducer for this crash yet.
>> >
>> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> > Reported-by: syzbot+87a05ae4accd500f5242@...kaller.appspotmail.com
>> >
>> > INFO: task hung in do_page_mkwriteINFO: task syz-fuzzer:4876 blocked for
>> > more than 140 seconds.
>> >       Not tainted 4.19.0-rc2-next-20180905+ #56
>> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> > syz-fuzzer      D21704  4876   4871 0x00000000
>> > Call Trace:
>> >  context_switch kernel/sched/core.c:2825 [inline]
>> >  __schedule+0x87c/0x1df0 kernel/sched/core.c:3473
>> >  schedule+0xfb/0x450 kernel/sched/core.c:3517
>> >  io_schedule+0x1c/0x70 kernel/sched/core.c:5140
>> >  wait_on_page_bit_common mm/filemap.c:1100 [inline]
>> >  __lock_page+0x5b7/0x7a0 mm/filemap.c:1273
>> >  lock_page include/linux/pagemap.h:483 [inline]
>> >  do_page_mkwrite+0x429/0x520 mm/memory.c:2391
>>
>> Waiting for page lock after ->page_mkwrite callback. Which means
>> ->page_mkwrite did not return VM_FAULT_LOCKED but 0. Looking into
>> linux-next... indeed "fs: convert return type int to vm_fault_t" has busted
>> block_page_mkwrite(). It has to return VM_FAULT_LOCKED and not 0 now.
>> Souptick, can I ask you to run 'fstests' for at least common filesystems
>> like ext4, xfs, btrfs when you change generic filesystem code please? That
>> would catch a bug like this immediately. Thanks.
>>
>
> "fs: convert return type int to vm_fault_t" is still under
> review/discusson and not yet merge
> into linux-next. I am not seeing it into linux-next tree.Can you
> please share the commit id ?

syzbot gave commit id in the report (see above)