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Date:   Wed, 12 Jul 2023 16:22:13 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Pintu Agarwal <pintu.ping@gmail.com>
Cc:     open list <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        linux-fsdevel@kvack.org, ezequiel@collabora.com, bjorn@mork.no
Subject: Re: MTD: Lots of mtdblock warnings on bootup logs
Message-ID: <20230712162213.79bc889c@xps-13>
In-Reply-To: <CAOuPNLizjBp_8ceKq=RLznXdsHD-+N55RoPh_D7_Mpkg7M-BwQ@mail.gmail.com>
References: <CAOuPNLizjBp_8ceKq=RLznXdsHD-+N55RoPh_D7_Mpkg7M-BwQ@mail.gmail.com>
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Hi Pintu,

pintu.ping@gmail.com wrote on Wed, 12 Jul 2023 19:29:39 +0530:

> Hi,
>=20
> We are getting below warning messages in dmesg logs on a NAND device
> for every raw partition.
> Kernel: 5.15 ; arm64 ; NAND + ubi + squashfs
> We have some RAW partitions and one UBI partition (with ubifs/squashfs vo=
lumes).
>=20
> We are seeing large numbers of these logs on the serial console that
> impact the boot time.
> [....]
> [    9.667240][    T9] Creating 58 MTD partitions on "1c98000.nand":
> [....]
> [   39.975707][  T519] mtdblock: MTD device 'uefi_a' is NAND, please
> consider using UBI block devices instead.
> [   39.975707][  T519] mtdblock: MTD device 'uefi_b' is NAND, please
> consider using UBI block devices instead.
> [....]
>=20
> This was added as part of this commit:
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/d=
rivers/mtd/mtdblock.c?h=3Dv5.15.120&id=3Df41c9418c5898c01634675150696da290f=
b86796
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/d=
rivers/mtd/mtdblock.c?h=3Dv5.15.120&id=3De07403a8c6be01857ff75060b2df9a1aa8=
320fe5
>=20
> I think this warning was decided after my last year's discussion about
> mtdblock vs ubiblock for squashfs.
>=20
> But these are raw NAND partitions and not mounted by us.
>=20
> What is the exact meaning of these warnings ?

mtdblock is legacy, ubiblock is better (on NAND devices).

> We have both these configs enabled:
> CONFIG_MTD_BLOCK=3Dy
> CONFIG_MTD_UBI_BLOCK=3Dy
>=20
> Through this warning, are we telling that only one of the above config
> should be enabled ?

If you don't need both, then yes.

> And the recommendation is to use ubi_block and disable mtd_block ?

Yes.

> We are already using ubiblock for mounting squashfs volumes.
> But how to get rid of these warnings for raw NAND partitions ?
>=20
> Is there a way to avoid or we are missing something which we are not awar=
e of?
>=20

In theory the warning should only appear if you open the device (IOW,
only if you use it). For this to happen, you need:
96a3295c351d ("mtdblock: warn if opened on NAND")
This commit was maybe not backported to stable kernels, you can send it
to stable@vger.kernel.org in order to ask for that. I also see that the
mtdblock_ro path was not corrected, maybe that's also a problem in your
case? Same, you can adapt the above patch and send it upstream.

Thanks,
Miqu=C3=A8l