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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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