On Mon, 2021-08-23 at 10:48 -0400, J. Bruce Fields wrote: > I'm seeing generic/154 failing sometimes. > > It does a "cp --reflink" (which uses FI_CLONE, which results in a > ->remap_file_range call that NFS maps to the CLONE operation), then > overwriting parts of the fire, and checking free blocks (with "stat -f > /path -c "%f") at various points, and failing when the number of free > blocks is outside an expected range. > > I don't know if it might be some caching issue, or something about how > NFS reports free blocks. > > Honestly it looks unlikely to be critical, so for now I'm ignoring > it.... > XFS backend? It could be speculative preallocation. The fact that NFS can defer closing the file (either due to delegations or due to the NFSv3 file cache) typically results in it taking longer for XFS to free up the blocks it preallocated. That again means it takes longer for the 'space used' to settle to the correct final value. https://linux-xfs.oss.sgi.narkive.com/jjjfnyI1/faq-xfs-speculative-preallocation -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
