On Sun, 2025-02-09 at 13:39 -0800, Rick Macklem wrote: > Hi, > > I thought I'd post here instead of nfsv4@xxxxxxxx since I > think the Linux server has been implementing this recently. > > I am not interested in making the FreeBSD NFSv4.1/4.2 > server dynamically resize slot tables in sessions, but I do > want to make sure the FreeBSD handles this case correctly. > > Here is what I believe is supposed to be done: > For growing the slot table... > - Server/replier sends SEQUENCE replies with both > sr_highest_slot and sr_target_highest_slot set to a larger value. > --> The client can then use those slots with > sa_sequenceid set to 1 for the first SEQUENCE operation on > each of them. > > For shrinking the slot table... > - Server/replier sends SEQUENCE replies with a smaller > value for sr_target_highest_slot. > - The server/replier waits for the client to do a SEQUENCE > operation on one of the slot(s) where the server has replied > with the smaller value for sr_target_highest_slot with a > sa_highest_slot value <= to the new smaller > sr_target_highest_slot > - Once this happens, the server/replier can set sr_highest_slot > to the lower value of sr_target_highest_slot and throw the > slot table entries above that value away. > --> Once the client sees a reply with sr_target_highest_slot set > to the lower value, it should not do any additional SEQUENCE > operations with a sa_slotid > sr_target_highest_slot > > Does the above sound correct? The above captures the case where the server is adjusting using OP_SEQUENCE. However there is another potential mode where the server sends out a CB_RECALL_SLOT. In the latter case, it is up to the client to send out enough SEQUENCE operations on the forward channel to implicitly acknowledges the change in slots using the sa_highestslot field (see RFC8881, Section 20.8.3). If the client was completely idle when it received the CB_RECALL_SLOT, it should only need to send out 1 extra SEQUENCE op, but if using RDMA, then it has to keep pounding out "RDMA send" messages until the RDMA credit count has been brought down too. -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
