On Mon, Sep 17, 2018 at 11:18:30PM -0400, Theodore Y. Ts'o wrote: > 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? As far as I know we don't have any general infrastructure -- ocfs2 has only recently been subjected to xfstests, and I don't think there are many people running xfstests on a xfs filesystem where realtime has been forced on for all files *and* the rt extent size is larger than a block. IOWs: we don't test hardly ever, it's probably broken, and sigh. :( --D > - Ted
