On Mon, Apr 10, 2017 at 02:37:50PM +0200, Jan Kara wrote: > I don't understand here. Do you want that all filesystems support NOWAIT > direct IO?
No. Per-file_system_type is way to coarse grained. All feature flag needs to be per-file_operation at least for cases like ext4 with our without extents (or journal) XFS v4 vs v5, different NFS versions, etc. For RWF_* each file operation simply declares if the feature is supported not by rejecting unknown ones. FIEMAP does the same as do a few other interfaces.
