Re: [PATCH 1/2] NFSD: Use nfsd_iter_read() when ->splice_read is not zero-copy

[Christoph Hellwig]

On Tue, Aug 18, 2026 at 02:08:10AM +0500, Ameer Hamza wrote:
> For some files splicing a READ cannot avoid a copy: gfs2, kernfs
> and the cifs direct-I/O modes use copy_splice_read() as their
> ->splice_read, and the VFS substitutes it for DAX files.
> copy_splice_read() allocates a fresh page for every page of
> payload and reads into it; nfsd_splice_actor() then installs
> those pages in rq_respages, displacing Reply pages the thread
> already owns. Both sets of pages are then freed.
> 
> Route these READs through nfsd_iter_read() instead. It performs

No.  None of the above are sensible use cases for NFSD exports.
There is no good reason to add a barely maintained special code path
thae pokes into internals for this.