On 12/5/24 7:43 PM, NeilBrown wrote:
If a client ever uses the highest available slot for a given session,
attempt to allocate more slots so there is room for the client to use
them 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.
Each time we increase the number of slots by 20% (rounded up). This
allows fairly quick growth while avoiding excessive over-shoot.
We would expect to stablise with around 10% more slots available than
the client actually uses.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
fs/nfsd/nfs4state.c | 40 +++++++++++++++++++++++++++++++++++-----
1 file changed, 35 insertions(+), 5 deletions(-)
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 67dfc699e411..ec4468ebbd40 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4235,11 +4235,6 @@ 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);
@@ -4289,6 +4284,41 @@ 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 20%. This allows
+ * fairly quick growth without grossly over-shooting what
+ * the client might use.
+ */
+ if (seq->slotid == session->se_fchannel.maxreqs - 1 &&
+ session->se_fchannel.maxreqs < NFSD_MAX_SLOTS_PER_SESSION) {
+ int s = session->se_fchannel.maxreqs;
+ int cnt = DIV_ROUND_UP(s, 5);
+
+ do {
+ /*
+ * 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 | __GFP_NOWARN))) {
+ s += 1;
+ session->se_fchannel.maxreqs = s;
+ } else {
+ kfree(slot);
Don't you want to break out of this loop if slot allocation or the
xa_store() fails? Does the session logic work if there is a gap
of unallocated slots in the slot table? Seems like we want to wait
a bit anyway after an allocation failure before asking again.
Otherwise, LGTM. I assume a v4 is forthcoming to address review
comments.
+ }
+ } while (slot && --cnt > 0);
+ }
+ seq->maxslots = session->se_fchannel.maxreqs;
+
out:
switch (clp->cl_cb_state) {
case NFSD4_CB_DOWN:
--
Chuck Lever
