Re: btrfs and default page sizes (4k vs 64k)
On 9/16/20 10:22 AM, Benjamin Block wrote:
On Wed, Sep 16, 2020 at 09:31:50AM -0500, Eric Sandeen wrote:
...
> Sub-page block support in filesystems is not a wild, esoteric,
unexpected
> feature.
>
These kinds of problems are not really that rare across different
Filesystems.
Try creating a XFS fs on a system with 64k PAGE_SIZE and a blocksize of
64k, then try mounting that fs on a x86_64 machine. It won't work:
https://elixir.bootlin.com/linux/v5.8/source/fs/xfs/xfs_mount.c#L165
And IIRC xfs is the default for RHEL, no?
It is. mkfs.xfs defaults to 4k blocks, so XFS filesystem are, by default,
compatible across all supported architectures. RHEL would not choose a
default fs with this sort of incompatibility across arches.
Block > page size is a different problem vs what is described in this
thread.
If you /manually/ create a large block size fs, overriding the defaults,
then yes you will have a compatibility problem on smaller page systems.
That's not the same as "you cannot create any btrfs filesystem that is
usable on both 4k and 64k page systems"
-Eric