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

[Hector Martin <marcan@marcan.st>]

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 ;)

- Hector