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From: Gao Xiang <hsiangkao@aol.com>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Richard Weinberger <richard@nod.at>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-erofs@lists.ozlabs.org,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: erofs: Question on unused fields in on-disk structs
Date: Thu, 22 Aug 2019 06:03:03 +0800	[thread overview]
Message-ID: <20190821220251.GA3954@hsiangkao-HP-ZHAN-66-Pro-G1> (raw)
In-Reply-To: <CAFLxGvxr2UMeVa29M9pjLtWMFPz7w6udRV38CRxEF1moyA9_Rw@mail.gmail.com>

Hi Richard,

On Wed, Aug 21, 2019 at 11:37:30PM +0200, Richard Weinberger wrote:
> Gao Xiang,
> 
> On Mon, Aug 19, 2019 at 10:45 PM Gao Xiang via Linux-erofs
> <linux-erofs@lists.ozlabs.org> wrote:
> > > struct erofs_super_block has "checksum" and "features" fields,
> > > but they are not used in the source.
> > > What is the plan for these?
> >
> > Yes, both will be used laterly (features is used for compatible
> > features, we already have some incompatible features in 5.3).
> 
> Good. :-)
> I suggest to check the fields being 0 right now.
> Otherwise you are in danger that they get burned if an mkfs.erofs does not
> initialize the fields.

Sorry... I cannot get the point...

super block chksum could be a compatible feature right? which means
new kernel can support it (maybe we can add a warning if such image
doesn't have a chksum then when mounting) but old kernel doesn't
care it.

Or maybe you mean these reserved fields? I have no idea all other
filesystems check these fields to 0 or not... But I think it should
be used with some other flag is set rather than directly use, right?

Thanks,
Gao Xiang

> 
> -- 
> Thanks,
> //richard

WARNING: multiple messages have this Message-ID (diff)
From: Gao Xiang via Linux-erofs <linux-erofs@lists.ozlabs.org>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Richard Weinberger <richard@nod.at>,
	linux-erofs@lists.ozlabs.org,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: erofs: Question on unused fields in on-disk structs
Date: Thu, 22 Aug 2019 06:03:03 +0800	[thread overview]
Message-ID: <20190821220251.GA3954@hsiangkao-HP-ZHAN-66-Pro-G1> (raw)
In-Reply-To: <CAFLxGvxr2UMeVa29M9pjLtWMFPz7w6udRV38CRxEF1moyA9_Rw@mail.gmail.com>

Hi Richard,

On Wed, Aug 21, 2019 at 11:37:30PM +0200, Richard Weinberger wrote:
> Gao Xiang,
> 
> On Mon, Aug 19, 2019 at 10:45 PM Gao Xiang via Linux-erofs
> <linux-erofs@lists.ozlabs.org> wrote:
> > > struct erofs_super_block has "checksum" and "features" fields,
> > > but they are not used in the source.
> > > What is the plan for these?
> >
> > Yes, both will be used laterly (features is used for compatible
> > features, we already have some incompatible features in 5.3).
> 
> Good. :-)
> I suggest to check the fields being 0 right now.
> Otherwise you are in danger that they get burned if an mkfs.erofs does not
> initialize the fields.

Sorry... I cannot get the point...

super block chksum could be a compatible feature right? which means
new kernel can support it (maybe we can add a warning if such image
doesn't have a chksum then when mounting) but old kernel doesn't
care it.

Or maybe you mean these reserved fields? I have no idea all other
filesystems check these fields to 0 or not... But I think it should
be used with some other flag is set rather than directly use, right?

Thanks,
Gao Xiang

> 
> -- 
> Thanks,
> //richard

  reply	other threads:[~2019-08-21 22:03 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-19 17:10 erofs: Question on unused fields in on-disk structs Richard Weinberger
2019-08-19 17:10 ` Richard Weinberger
2019-08-19 17:10 ` Richard Weinberger
2019-08-19 20:45 ` Gao Xiang
2019-08-19 20:45   ` Gao Xiang via Linux-erofs
2019-08-21 21:37   ` Richard Weinberger
2019-08-21 21:37     ` Richard Weinberger
2019-08-21 22:03     ` Gao Xiang [this message]
2019-08-21 22:03       ` Gao Xiang via Linux-erofs
2019-08-22  8:33       ` Richard Weinberger
2019-08-22  8:33         ` Richard Weinberger
2019-08-22  9:05         ` Gao Xiang
2019-08-22  9:05           ` Gao Xiang
2019-08-22  9:08           ` Gao Xiang
2019-08-22  9:08             ` Gao Xiang
2019-08-22 14:21         ` Theodore Y. Ts'o
2019-08-22 14:21           ` Theodore Y. Ts'o
2019-08-22 14:29           ` Richard Weinberger
2019-08-22 14:29             ` Richard Weinberger
2019-08-22 14:38             ` Gao Xiang
2019-08-22 14:38               ` Gao Xiang
2019-08-22 14:34           ` Gao Xiang
2019-08-22 14:34             ` Gao Xiang

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