If a client ever uses the highest available slot for a given session, attempt to allocate another slot so there is room for the client to use more slots if wanted. GFP_NOWAIT is used so if there is not plenty of free memory, failure is expected - which is what we want. It also allows the allocation while holding a spinlock. We would expect to stablise with one more slot available than the client actually uses. Now that we grow the slot table on demand we can start with a smaller allocation. Define NFSD_MAX_INITIAL_SLOTS and allocate at most that many when session is created. Signed-off-by: NeilBrown <neilb@xxxxxxx> --- fs/nfsd/nfs4state.c | 32 ++++++++++++++++++++++++++------ fs/nfsd/state.h | 2 ++ 2 files changed, 28 insertions(+), 6 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 31ff9f92a895..fb522165b376 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1956,7 +1956,7 @@ static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fattrs, if (!slot || xa_is_err(xa_store(&new->se_slots, 0, slot, GFP_KERNEL))) goto out_free; - for (i = 1; i < numslots; i++) { + for (i = 1; i < numslots && i < NFSD_MAX_INITIAL_SLOTS; i++) { slot = kzalloc(slotsize, GFP_KERNEL | __GFP_NORETRY); if (!slot) break; @@ -4248,11 +4248,6 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, slot = xa_load(&session->se_slots, seq->slotid); dprintk("%s: slotid %d\n", __func__, seq->slotid); - /* We do not negotiate the number of slots yet, so set the - * maxslots to the session maxreqs which is used to encode - * sr_highest_slotid and the sr_target_slot id to maxslots */ - seq->maxslots = session->se_fchannel.maxreqs; - trace_nfsd_slot_seqid_sequence(clp, seq, slot); status = check_slot_seqid(seq->seqid, slot->sl_seqid, slot->sl_flags & NFSD4_SLOT_INUSE); @@ -4302,6 +4297,31 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, cstate->session = session; cstate->clp = clp; + /* + * If the client ever uses the highest available slot, + * gently try to allocate another one. + */ + if (seq->slotid == session->se_fchannel.maxreqs - 1 && + session->se_fchannel.maxreqs < NFSD_MAX_SLOTS_PER_SESSION) { + int s = session->se_fchannel.maxreqs; + + /* + * GFP_NOWAIT is a low-priority non-blocking allocation + * which can be used under client_lock and only succeeds + * if there is plenty of memory. + * Use GFP_ATOMIC which is higher priority for xa_store() + * so we are less likely to waste the effort of the first + * allocation. + */ + slot = kzalloc(slot_bytes(&session->se_fchannel), GFP_NOWAIT); + if (slot && !xa_is_err(xa_store(&session->se_slots, s, slot, + GFP_ATOMIC))) + session->se_fchannel.maxreqs += 1; + else + kfree(slot); + } + seq->maxslots = session->se_fchannel.maxreqs; + out: switch (clp->cl_cb_state) { case NFSD4_CB_DOWN: diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index e97626916a68..a14a823670e9 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -249,6 +249,8 @@ static inline struct nfs4_delegation *delegstateid(struct nfs4_stid *s) * get good throughput on high-latency servers. */ #define NFSD_MAX_SLOTS_PER_SESSION 2048 +/* Maximum number of slots per session to allocate for CREATE_SESSION */ +#define NFSD_MAX_INITIAL_SLOTS 32 /* Maximum session per slot cache size */ #define NFSD_SLOT_CACHE_SIZE 2048 /* Maximum number of NFSD_SLOT_CACHE_SIZE slots per session */ -- 2.47.0