Re: [PATCH] btrfs: disable zstd support for i386-pc

From: Daniel Kiper <dkiper@net-space.pl>
To: Michael Chang <MChang@suse.com>
Cc: The development of GNU GRUB <grub-devel@gnu.org>,
	Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>,
	"dave@jikos.cz" <dave@jikos.cz>,
	"pmenzel@molgen.mpg.de" <pmenzel@molgen.mpg.de>,
	"terrelln@fb.com" <terrelln@fb.com>
Subject: Re: [PATCH] btrfs: disable zstd support for i386-pc
Date: Tue, 3 Mar 2020 17:59:12 +0100	[thread overview]
Message-ID: <20200303165912.oqj6ac662sbl4y2q@tomti.i.net-space.pl> (raw)
In-Reply-To: <20191119083404.GA7871@mazu>

On Tue, Nov 19, 2019 at 08:34:12AM +0000, Michael Chang wrote:
> On Fri, Nov 15, 2019 at 12:42:52PM +0100, Daniel Kiper wrote:
> > On Thu, Nov 14, 2019 at 09:53:54AM +0000, Michael Chang wrote:
> > > On Wed, Nov 13, 2019 at 12:00:50PM +0100, Daniel Kiper wrote:
> > > > On Thu, Nov 07, 2019 at 12:52:35PM +0100, Daniel Kiper wrote:
> > > > > On Wed, Nov 06, 2019 at 11:15:04AM -0800, Vladimir 'phcoder' Serbinenko wrote:
> > > > > > Please don't do it this way. The right solution is to move it to separate
> > > > > > module and include zstd module when needed. Not everybody uses btrfs
> > > > > > embedded area. I recommend not to use it. Using mbr gap or BBP is the
> > > > > > recommended way.
> > > > >
> > > > > I will put the cat among the pigeons. Maybe we should finally stop
> > > > > pretending that the GRUB supports small MBR gaps. Otherwise we will
> > > > > be fighting with such issues endlessly.
> > > >
> > > > Bumping the thread... Nobody objects? Hmmm...
> > >
> > > I don't think we are able to give up MBR gap support, simply because no
> > > other way out in creating the area for bootloader embedding. However we
> >
> > Nope, I do not propose that...
> >
> > > should consider to correct this claim in manual.
> > >
> > >  "You must ensure that the first partition starts at least 31 KiB (63
> > >  sectors) from the start of the disk"
> > >
> > > to reflect the fact that 31 KiB is no longer applicable and the ideal
> > > size should be above 1MB (or such). You should go check with your disk
> > > tools to find the suitable parameter to fulfill the requirement, for eg,
> > > the partition alignment would mostly affect this.
> >
> > Exactly! However, there are some legacy systems which do not boot if MBR
> > gap does not end at 63 sectors boundary. Hence, maybe we should suggest
> > chainloading, using e.g. SYSLINUX, in a such cases. Anyway, may I ask
> > you to prepare a patch for GRUB manual which describes the problem?
>
> Alright, sounds good to me. :)

Michael, ping? I would like to see this limitation documented in 2.06.
Could you do that?

Daniel