Re: [PATCH v4 0/1] Enforce 4k sectorize by default for mkfs

From: Neal Gompa <neal@gompa.dev>
To: Qu Wenruo <wqu@suse.com>
Cc: Hector Martin <marcan@marcan.st>,
	Josef Bacik <josef@toxicpanda.com>,
	 Linux BTRFS Development <linux-btrfs@vger.kernel.org>,
	Anand Jain <anand.jain@oracle.com>,
	 Qu Wenruo <quwenruo.btrfs@gmx.com>,
	David Sterba <dsterba@suse.cz>,  Sven Peter <sven@svenpeter.dev>,
	Davide Cavalca <davide@cavalca.name>, Jens Axboe <axboe@fb.com>,
	 Asahi Lina <lina@asahilina.net>,
	Asahi Linux <asahi@lists.linux.dev>
Subject: Re: [PATCH v4 0/1] Enforce 4k sectorize by default for mkfs
Date: Tue, 28 Nov 2023 16:24:27 -0500	[thread overview]
Message-ID: <CAEg-Je8r0K0k8UMcAafxXyrNuxJrxJbGhkwvo10pUw+rxhCa8g@mail.gmail.com> (raw)
In-Reply-To: <f229058e-4f5d-4bd0-9016-41b133688443@suse.com>

On Tue, Nov 28, 2023 at 2:57 PM Qu Wenruo <wqu@suse.com> wrote:
>
>
>
> On 2023/11/29 01:31, Hector Martin wrote:
> >
> >
> > On 2023/11/28 1:07, Josef Bacik wrote:
> >> On Thu, Nov 16, 2023 at 11:02:23AM -0500, Neal Gompa wrote:
> >>> The Fedora Asahi SIG[0] is working on bringing up support for
> >>> Apple Silicon Macintosh computers through the Fedora Asahi Remix[1].
> >>>
> >>> Apple Silicon Macs are unusual in that they currently require 16k
> >>> page sizes, which means that the current default for mkfs.btrfs(8)
> >>> makes a filesystem that is unreadable on x86 PCs and most other ARM
> >>> PCs.
> >>>
> >>> This is now even more of a problem within Apple Silicon Macs as it is now
> >>> possible to nest 4K Fedora Linux VMs on 16K Fedora Asahi Remix machines to
> >>> enable performant x86 emulation[2] and the host storage needs to be compatible
> >>> for both environments.
> >>>
> >>> Thus, I'd like to see us finally make the switchover to 4k sectorsize
> >>> for new filesystems by default, regardless of page size.
> >>>
> >>> The initial test run by Hector Martin[3] at request of Qu Wenruo
> >>> looked promising[4], and we've been running with this behavior on
> >>> Fedora Linux since Fedora Linux 36 (at around 6.2) with no issues.
> >>>
> >>
> >> This is a good change and well documented.  This isn't being ignored, it's just
> >> a policy change that we have to be conservative about considering.  We only in
> >> the last 3 months have added a Apple Silicon machine to our testing
> >> infrastructure (running Fedora Asahi fwiw) to make sure we're getting consistent
> >> subpage-blocksize testing.  Generally speaking it's been fine, we've fixed a few
> >> things and haven't broken anything, but it's still comes with some risks when
> >> compared to the default of using the pagesize.
> >>
> >> We will continue to discuss this amongst ourselves and figure out what we think
> >> would be a reasonable timeframe to make this switch and let you know what we're
> >> thinking ASAP.  Thanks,
> >
> > Reminder that the Raspberry Pi 5 is also shipping with 16K pages by
> > default now. The clock is ticking for an ever-growing stream of people
> > upset that they can't mount/data-rescue/etc their rPi5 NAS disks from an
> > x86 machine ;)
>
> As long as they are using 5.15+ kernel, they should be able to mount and
> use their RPI NAS with disks from x86 machines.
>
> The change is only for the default mkfs options.
>

Right, and the thing is, it's fairly common for the disks to be
formatted from a Raspberry Pi. So until some kind of support for using
any sector size on any architecture regardless of page size lands,
this is going to be a big problem.

-- 
真実はいつも一つ！/ Always, there's only one truth!