linux-ext4 - Re: [PATCH] libfs: Fix DIO mode aligment

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Date:   Mon, 1 Mar 2021 12:42:22 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     Благодаренко Артём 
        <artem.blagodarenko@...il.com>
Cc:     linux-ext4@...r.kernel.org, adilger.kernel@...ger.ca,
        Alexey Lyashkov <alexey.lyashkov@....com>
Subject: Re: [PATCH] libfs: Fix DIO mode aligment

On Mon, Mar 01, 2021 at 07:14:00PM +0300, Благодаренко Артём wrote:
> Here is how I reproduced it originally (without the patch)
> 
> # truncate -s 512MB /tmp/lustre-ost
> # losetup -b 4096 /dev/loop0 /tmp/lustre-ost
> # mkfs.ext4 /dev/loop0

Thanks for pointing out that this can be tested using losetup.

> With your patch e2image works fine.
> 
> [root@...2 e2fsprogs-kernel]# git rev-parse HEAD
> 67f2b54667e65cf5a478fcea8b85722be9ee6e8d
> [root@...2 e2fsprogs-kernel]# misc/e2image /dev/loop0 /tmp/ost-image
> e2image 1.46.1 (9-Feb-2021)

So commit 67f2b54667e6 is 1.46.2, so I'm not sure that you recompiled
e2image.  More importantly, e2image in upstream doesn't use Direct
I/O.  When I tried using debugfs -D, it looks like Direct I/O on an
Advanced Format HDD isn't working correctly:

# debugfs -D /dev/loop0
debugfs 1.46.2 (28-Feb-2021)
debugfs: Bad magic number in super-block while trying to open /dev/loop0
/dev/loop0 contains a ext4 file system
        created on Mon Mar  1 12:31:43 2021

This isn't a regression since it was broken in upstream before, but it
would be good to get this fixed before e2fsprogs 1.46.3.

Cheers,

						- Ted