NFSD: Use xdrgen XDR functions for NFSv2 READDIR results

READDIR is the last NFSv2 procedure whose reply is still produced by
a hand-written encoder. Its entry list is the value-follows form of
RFC 1094's "entry *entries" -- each entry prefixed by TRUE, the
sequence closed by FALSE -- streamed straight from the directory as
it is read rather than from a materialized array. The generated
encoder could not drive that: the union encoder writes the reply
status word before the entry list, yet a streamed read does not learn
the status until the directory has been read, and the aggregate loop
was bounded by a count the begin hook had to supply up front.

The preceding patches remove both obstacles. The optional-data
aggregate encoder now pulls entries until the hook signals end, so no
count is needed, and the streaming directory reader yields one entry
at a time during encode. Mark readdirok's entry list as an aggregate
and regenerate; the struct definitions stay the verbatim RFC 1094
types, and the lone "pragma aggregate readdirok entries" selects the
hook-driven codec.

Split the read across the two phases so the generated encoder owns
the framing. nfsd_proc_readdir() opens the directory, where an open
error becomes the reply status the union encoder then writes, and the
encode hooks stream the entries: each pull reserves a placeholder
cookie and back-patches the preceding entry's cookie once the
following entry's resume offset is known; the end hook back-patches
the final cookie and reports eof. nfssvc_release_readdirres() closes
the reader and releases the file handle. The decode hooks are stubs
-- a server never decodes a READDIR result -- present only to satisfy
the generated decoder's linkage.

Retire struct nfsd_readdirres for an embedded struct readdirres so
the RPC dispatch layer can cast the response to its xdrgen type.
The directory's svc_fh moves into that wrapper and struct
readdirargs_wrapper goes away. svc_process() zeroes the result buffer
before decode but leaves the argument buffer as the previous request
left it, and ->pc_release runs even when decoding fails. A file
handle kept in the argument wrapper would reach fh_put() on that path
uninitialized.

The generated encoder reserves reply space through the xdr_stream,
which does not advance rq_next_page as it moves onto the next page.
svcrdma retains only the pages below rq_next_page across Send
completion, so the end hook sets rq_next_page past the last page the
reply uses, as nfsd4_encode_operation() does.

A host error during the streamed read cannot retract entries already
on the wire, so it ends the list as a truncated, non-eof reply rather
than an error status; an error opening the directory is still
reported as the reply status. The bytes on the wire are otherwise
unchanged.

Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260916162859.2051-30-cel@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

0 files changed, 0 insertions, 0 deletions