nfsd: make the copy offload stateid a first-class nfs4_stid

The async COPY offload stateid was a copy_stateid_t in the per-net
nn->s2s_cp_stateids IDR, sharing that table with COPY_NOTIFY stateids even
though every reader (laundromat, manage_cpntf_state()) accepts only
NFS4_COPYNOTIFY_STID. It was inserted there only to mint a unique so_id;
OFFLOAD_CANCEL and OFFLOAD_STATUS find the copy by walking
clp->async_copies.

Building on the nfsd4_async_copy split, promote it to a first-class
nfs4_stid (SC_TYPE_COPY) embedded at the head of nfsd4_async_copy and
allocated from the client's cl_stateids via nfs4_alloc_stid(). This:

  - makes the stateid per-client by construction rather than relying on a
    guessable cyclic id in a global table;

  - reuses the common id allocation, refcounting, and teardown
    (nfs4_put_stid() + sc_free), removing the bespoke
    nfs4_init_copy_state()/nfs4_free_copy_state(); and

  - leaves nn->s2s_cp_stateids exclusively for COPY_NOTIFY stateids.

The async-copy lifetime model is unchanged; nf4_put_copy() now drops the
stid's single reference, which removes it from cl_stateids and frees the
slab.

Per RFC 7862 Section 4.8 a copy offload stateid is valid only for
COPY/OFFLOAD_CANCEL/OFFLOAD_STATUS/CB_OFFLOAD, not FREE_STATEID or
TEST_STATEID, so find_stateid_locked() hides SC_TYPE_COPY and those paths
keep returning bad_stateid as before. Its seqid MUST NOT be zero, so set
si_generation to 1 (nfs4_alloc_stid() leaves it zero).

Follow-ups (not done here): NFS4_COPY_STID, the now-always-COPYNOTIFY
branch in nfs4_init_cp_state(), and the redundant cs_type checks in the
laundromat and manage_cpntf_state() are vestigial.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260710-nfsd-testing-v3-9-a0ff7db6aa3e@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

0 files changed, 0 insertions, 0 deletions