linux-ext4 - Re: [PATCH] e2image: copy mmp block when create metadata only image

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Message-ID: <20180821191648.GE4723@thunk.org>
Date:   Tue, 21 Aug 2018 15:16:48 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     c17828 <artem.blagodarenko@...il.com>
Cc:     linux-ext4@...r.kernel.org, adilger.kernel@...ger.ca,
        alexey.lyashkov@...il.com
Subject: Re: [PATCH] e2image: copy mmp block when create metadata only image

On Tue, Aug 21, 2018 at 04:50:44PM +0300, c17828 wrote:
> From: Artem Blagodarenko <artem.blagodarenko@...il.com>
> 
> e2image in modes without data blocks copy (-r, -Q) doesn't copy
> mmp block that leads to fsck error:
> 
> Superblock has invalid MMP magic.  Fix? no
> 
> This patch adds coping this block if mmp is enabled.
> 
> Change-Id: I66035ee394a0ff53b9959e82b3e47050f3bf1593
> Signed-off-by: Artem Blagodarenko <artem.blagodarenko@...il.com>

You need to override the location of the temporary file used by the
test, because mmp uses O_DIRECT, and O_DIRECT doesn't work on tmpfs.
Hence the new test you added (thanks for adding a regression test)
fails on developers' systems which have a tmpfs mounted on /tmp:

% mke2fs -q -F -o Linux -b 4096 -O mmp -E mmp_update_interval=1 /tmp/foo.img 100
mke2fs: MMP: open with O_DIRECT failed while writing out and closing file system

Take a look at how the test m_mmp_bad_csum handles this:

# use current directory instead of /tmp becase tmpfs doesn't support DIO
rm -f $TMPFILE
TMPFILE=$(mktemp ./tmp-$test_name.XXXXXX)

Could you fix and resend?  Thanks!

						- Ted