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
