linux-kernel - Re: [Regression] ext4: changes to mb_optimize

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Message-ID: <20220815103452.7hjx7ohzx64e5lex@quack3>
Date:   Mon, 15 Aug 2022 12:34:52 +0200
From:   Jan Kara <jack@...e.cz>
To:     Stefan Wahren <stefan.wahren@...e.com>
Cc:     Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
        Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>,
        Theodore Ts'o <tytso@....edu>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        linux-fsdevel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Geetika.Moolchandani1@....com, regressions@...ts.linux.dev
Subject: Re: [Regression] ext4: changes to mb_optimize_scan cause issues on
 Raspberry Pi

Hi Stefan,

Back from vacation...

On Sun 31-07-22 22:42:56, Stefan Wahren wrote:
> Hi Jan,
> 
> Am 28.07.22 um 12:00 schrieb Jan Kara:
> > 
> > Also can get filesystem metadata image of your card like:
> >    e2image -r <fs-device> - | gzip >/tmp/ext4-image.gz
> > 
> > and put it somewhere for download? The image will contain only fs metadata,
> > not data so it should be relatively small and we won't have access to your
> > secrets ;). With the image we'd be able to see how the free space looks
> > like and whether it perhaps does not trigger some pathological behavior.
> i've problems with this. If i try store uncompressed the metadata of the
> second SD card partition (/dev/sdb2 = rootfs) the generated image file is
> nearly big as the whole partition. In compressed state it's 25 MB. Is this
> expected?

Yes, that is expected. The resulting file is a sparse file that contains
only metadata blocks that is the reason why it compresses so well but looks
big.

								Honza

-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR