On Thu, 25 Apr 2019 17:23:56 +1000, ronnie sahlberg wrote: > Folks. > > In the cifs client we use FSCTL_SET_ZERO_DATA when userspace wants to > punch a hole in a file. SET_ZERO_DATA maps quite well to the > PUNCH_HOLE semantics in that it will deallocate what it can and > overwrite what it can not with 0. Cool, I'd be interested to hear how things go when testing against a Samba SMB2+ server - it similarly maps FSCTL_SET_ZERO_DATA to PUNCH_HOLE. > On windows 16/ntfs the deallocate blocksize is 64k. > > Does anyone know if this is always 64k or if there is a way to query > the server for this? smbtorture4 includes a sparse_hole_dealloc test for checking this via incremental ZERO_DATA + QAR requests: https://git.samba.org/?p=samba.git;a=blob;f=source4/torture/smb2/ioctl.c#l3981 I don't recall seeing anything non-64k at the time, but I didn't check that thoroughly. Cheers, David
