Re: [BUG 4.10-rc7] sb_fdblocks inconsistency in xfs/297 test

On Fri 10-02-17 11:53:48, Eryu Guan wrote:

Hi,

I was testing 4.10-rc7 kernel and noticed that xfs_repair reported XFS
corruption after fstests xfs/297 test. This didn't happen with 4.10-rc6
kernel, and git bisect pointed the first bad commit to

commit d1908f52557b3230fbd63c0429f3b4b748bf2b6d
Author: Michal Hocko [off-list ref]
Date:   Fri Feb 3 13:13:26 2017 -0800

    fs: break out of iomap_file_buffered_write on fatal signals

    Tetsuo has noticed that an OOM stress test which performs large write
    requests can cause the full memory reserves depletion.  He has tracked
    this down to the following path
....

It's the sb_fdblocks field reports inconsistency:
...
Phase 2 - using internal log   
        - zero log...
        - scan filesystem freespace and inode maps...
sb_fdblocks 3367765, counted 3367863
        - 11:37:41: scanning filesystem freespace - 16 of 16 allocation groups done
        - found root inode chunk
...

And it can be reproduced almost 100% with all XFS test configurations
(e.g. xfs_4k xfs_2k_reflink), on all test hosts I tried (so I didn't
bother pasting my detailed test and host configs, if more info is needed
please let me know).

The patch can lead to short writes when the task is killed. Was there
any OOM killer triggered during the test? If not who is killing the
task? I will try to reproduce later today.
-- 
Michal Hocko
SUSE Labs