Re: [PATCH V3 01/19] Fix xfs/009 to work with 64k block size

Theodore Y. Ts'o
2018-09-18T08:49:04Z

On Mon, Sep 17, 2018 at 03:59:25PM -0700, Darrick J. Wong wrote:
>
> Hm. Certain filesystems draw a distinction between the fundamental
> block size and the minimum file block mapping size. ocfs2 supports
> having a file cluster size (mkfs.ocfs2 -C) that is greater than the fs
> block size, and (I think) xfs can achieve something similar for files on
> a realtime device via the mkfs.xfs -r extsize= option.
>
> If you're dealing with writing things into a file for a test, I think
> you have to use _get_file_block_size to make sure that you don't fall
> afoul of the cluster/block difference. I don't know if you've checked
> that for this patch series...?
>
> (Granted, I suspect that many tests have been sloppy about this...)

Indeed, we have a number of failures in ext4 bigalloc which are
because of this block size vs. cluster size difference. IIRC, a while
back Eric Whitney had tried to start a discussion about how to best
deal with this issue, but it wasn't clear what was the right way to
add the necessary infrastructure to xfstests. I had assumed it was an
ext4-only problem, and no one had time to try to come up with a
solution.

As far as I know, we still don't have any general infrastructure to
support this in xfstests. Is this correct, or am I missing something?

- Ted