linux-kernel - Re: Kernel 4.14: Using dm-verity with squashfs rootfs

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Date:   Wed, 21 Jul 2021 20:30:38 +0530
From:   Pintu Agarwal <pintu.ping@...il.com>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     open list <linux-kernel@...r.kernel.org>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>, dm-devel@...hat.com,
        Kernelnewbies <kernelnewbies@...nelnewbies.org>, agk@...hat.com,
        snitzer@...hat.com, shli@...nel.org,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: Kernel 4.14: Using dm-verity with squashfs rootfs - mounting issue

On Tue, 20 Jul 2021 at 17:12, Mikulas Patocka <mpatocka@...hat.com> wrote:
>
> Hi
>
> Try to set up dm-verity with block size 512 bytes.
>
> I don't know what block size does squashfs use, but if the filesystem
> block size is smaller than dm-verity block size, it doesn't work.
>
Okay thank you so much for this clue,
It seems we are using 65536 as the squashfs block size:
==> mksquashfs [...] - comp xz -Xdict-size 32K -noI -Xbcj arm -b 65536
-processors 1

But for dm-verity we are giving block size of 4096
==> [    0.000000] Kernel command line:[..] verity="96160 12020
d7b8a7d0c01b9aec888930841313a81603a50a2a7be44631c4c813197a50d681 0 "
rootfstype=squashfs root=/dev/mtdblock34 ubi.mtd=30,0,30 [...]
root=/dev/dm-0 dm="system none ro,0 96160 verity 1 /dev/mtdblock34
/dev/mtdblock39 4096 4096 12020 8 sha256
d7b8a7d0c01b9aec888930841313a81603a50a2a7be44631c4c813197a50d681
aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7"

Now, we are checking by giving squashfs block size also as 4096

In case, if this does not work, what else could be the other option ?
Can we try with initramfs approach ?

Thanks,
Pintu