linux-ext4 - Re: [e2fsprogs PATCH v2] resize2fs: use directio when reading superblock

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Date:   Mon, 18 Sep 2023 14:36:43 -0700
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     Krister Johansen <kjlx@...pleofstupid.com>,
        Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [e2fsprogs PATCH v2] resize2fs: use directio when reading
 superblock

Hi Andreas,

On Mon, Sep 18, 2023 at 03:20:01PM -0600, Andreas Dilger wrote:
> On Sep 11, 2023, at 12:39 PM, Krister Johansen <kjlx@...pleofstupid.com> wrote:
> > 
> > Invocations of resize2fs intermittently report failure due to superblock
> > checksum mismatches in this author's environment.  This might happen a few
> > times a week.  The following script can make this happen within minutes.
> > (It assumes /dev/nvme1n1 is available and not in use by anything else).
> 
> Krister,
> thanks for submitting the patch.  This particular issue was already fixed
> in commit v1.46.6-16-g43a498e93888, apparently based on your previous report:
> 
>     commit 43a498e938887956f393b5e45ea6ac79cc5f4b84
>     Author:     Theodore Ts'o <tytso@....edu>
>     AuthorDate: Thu Jun 15 00:17:01 2023 -0400
>     Commit:     Theodore Ts'o <tytso@....edu>
>     CommitDate: Thu Jun 15 00:17:01 2023 -0400
> 
>     resize2fs: use Direct I/O when reading the superblock for online resizes
> 
>     If the file system is mounted, the superblock can be changing while
>     resize2fs is trying to read the superblock, resulting in checksum
>     failures.  One way of avoiding this problem is read the superblock
>     using Direct I/O, since the kernel makes sure that what gets written
>     to disk is self-consistent.
> 
>     Suggested-by: Krister Johansen <kjlx@...pleofstupid.com>
>     Signed-off-by: Theodore Ts'o <tytso@....edu>
> 
> So it is landed on the e2fsprogs maint branch, but there has not been a
> maintenance release since the patch was landed.

Thanks for the response. My apologies for resubmitting this.  I had
thought that I checked the git trees before sending this out, but I
must've looked at the wrong one.  Sorry about that.

Thanks to Ted for applying his reworked patch, it's much appreciated.

-K