linux-ext4 - Re: [PATCH v3] ext4: fix bug for rename with RENAME

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Date:   Fri, 22 Jan 2021 22:32:48 +0200
From:   Amir Goldstein <amir73il@...il.com>
To:     harshad shirwadkar <harshadshirwadkar@...il.com>
Cc:     Miklos Szeredi <miklos@...redi.hu>,
        "Theodore Ts'o" <tytso@....edu>, yangerkun <yangerkun@...wei.com>,
        Ext4 <linux-ext4@...r.kernel.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, "zhangyi (F)" <yi.zhang@...wei.com>,
        lihaotian <lihaotian9@...wei.com>, lutianxiong@...wei.com,
        linfeilong <linfeilong@...wei.com>,
        fstests <fstests@...r.kernel.org>,
        Vijaychidambaram Velayudhan Pillai <vijay@...utexas.edu>
Subject: Re: [PATCH v3] ext4: fix bug for rename with RENAME_WHITEOUT

On Fri, Jan 22, 2021 at 9:21 PM harshad shirwadkar
<harshadshirwadkar@...il.com> wrote:
>
> Thanks Amir for pointing that out. Yes we are missing fast commit
> tracking in whiteout. I'll send out a fix for that.
>
> > But I must say it would have been very hard to catch missing ext4_fc_track_*
> > without specialized fs fuzzer such as the CrashMonkey generated tests.
>
> I agree, it's been on my to-do list to run CrashMonkey tests with fast
> commits. I'm curious what kind of CrashMonkey tests you ran that
> helped you catch this? Were you running Overlayfs on top of Ext4 with
> fast commits?
>

Neither. I just guessed RENAME_WHITEOUT might be missed as
developers are rarely aware of it.
I never ran CrashMonkey tests myself.
I found a few crash consistency bugs using xfstest generic/455.
I suggest that you run it with fast commits
and try using NUM_OPS and NUM_FILES larger than the test defaults
to let the test run for a longer time.

Thanks,
Amir.