Re: [Libguestfs] nbdkit: how to require use of filter

On May 03 2022, rjones at redhat.com (Richard W.M. Jones) wrote: > On Mon, May 02, 2022 at 10:25:44AM +0100, Nikolaus Rath wrote: >> Hi, >> >> Is there a way for a nbdkit plugin to *require* use of a nbdkit filter >> (specifically the nbdkit-blocksize-filter) programmatically? > > No it's not possible in general, you just have to document it. > > However as it's *blocksize* filter that you're talking about, I assume > you mean that your filter has blocksize constraints, eg. that it > cannot handle sub-sector requests. In this case it is possible to > tell clients that they must not issue requests smaller than a certain > size (and also hint about optimal and maximum sizes). You can do this > by writing a .block_size callback. For example: > > https://gitlab.com/nbdkit/nbdkit/-/blob/1f5dc0679e570ca2fa149ceaa52922d70... > > Not all clients obey these (although these clients are buggy!) Do you happen to know if the kernel's NBD client obeys them?

(I assume setting a blocksize constraint implies an alignment constraint as well?)