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

[Qu Wenruo <wqu@suse.com>]

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.

Thanks,
Qu
> 
> - Hector