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SubjectRe: linux-next test error
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@syzkaller.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.

Honza

--
Jan Kara <jack@suse.com>
SUSE Labs, CR

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