On 1/24/2025 9:11 AM, Jeff Layton wrote:
On Fri, 2025-01-24 at 09:00 -0500, J. Bruce Fields wrote:
On Thu, Jan 23, 2025 at 06:20:08PM -0500, Jeff Layton wrote:
On Thu, 2025-01-23 at 17:18 -0500, Chuck Lever wrote:
On 1/23/25 3:25 PM, Jeff Layton wrote:
RFC8881, 15.1.1.3 says this about NFS4ERR_DELAY:
"For any of a number of reasons, the replier could not process this
operation in what was deemed a reasonable time. The client should wait
and then try the request with a new slot and sequence value."
A little farther down, Section 15.1.1.3 says this:
"If NFS4ERR_DELAY is returned on a SEQUENCE operation, the request is
retried in full with the SEQUENCE operation containing the same slot
and sequence values."
And:
"If NFS4ERR_DELAY is returned on an operation other than the first in
the request, the request when retried MUST contain a SEQUENCE operation
that is different than the original one, with either the slot ID or the
sequence value different from that in the original request."
My impression is that the slot needs to be held and used again only if
the server responded with NFS4ERR_DELAY on the SEQUENCE operation. If
the NFS4ERR_DELAY was the status of the 2nd or later operation in the
COMPOUND, then yes, a different slot, or the same slot with a bumped
sequence number, must be used.
The current code in nfsd4_cb_sequence_done() appears to be correct in
this regard.
Ok! I stand corrected. We should be able to just drop this patch, but
some of the later patches may need some trivial merge conflicts fixed
up.
Any idea why SEQUENCE is different in this regard?
Isn't DELAY on SEQUENCE an indication that the operation is still in
progress? The difference between retrying the same slot or not is
whether you're asking the server again for the result of the previous
operation, or whether you're asking it to perform a new one.
If you get DELAY on a later op and then keep retrying with the same
seqid/slot then I'd expect you to get stuck in an infinite loop getting
a DELAY response out of the reply cache.
Hi Bruce!
That may be the case. From RFC8881, section 2.10.6.2:
"A retry might be sent while the original request is still in progress
on the replier. The replier SHOULD deal with the issue by returning
NFS4ERR_DELAY as the reply to SEQUENCE or CB_SEQUENCE operation, but
implementations MAY return NFS4ERR_MISORDERED. Since errors from
SEQUENCE and CB_SEQUENCE are never recorded in the reply cache, this
approach allows the results of the execution of the original request to
be properly recorded in the reply cache (assuming that the requester
specified the reply to be cached)."
It's true, but note that the NFS4ERR_DELAY response is a SHOULD, so it's
not the complete picture. It seems rude to return MISORDERED as suggested,
but it's just as possible that the server may not respond at all, and
simply wait for the in-progress operation to complete. We certainly
can't count on all servers to do the same thing.
Tom.
This rule seems a
bit arbitrary. If the response is NFS4ERR_DELAY, then why would it
matter which slot you use when retransmitting? The responder is just
saying "go away and come back later".
What if the responder repeatedly returns NFS4ERR_DELAY (maybe because
it's under resource pressure), and also shrinks the slot table in the
meantime? It seems like that might put the requestor in an untenable
position.
Maybe we should lobby to get this changed in the spec?
This is CB_SEQUENCE, but I believe the same rule applies. Release the
slot before submitting the delayed RPC.
Fixes: 7ba6cad6c88f ("nfsd: New helper nfsd4_cb_sequence_done() for processing more cb errors")
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/nfsd/nfs4callback.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index bfc9de1fcb67b4f05ed2f7a28038cd8290809c17..c26ccb9485b95499fc908833a384d741e966a8db 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1392,6 +1392,7 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
goto need_restart;
case -NFS4ERR_DELAY:
cb->cb_seq_status = 1;
+ nfsd41_cb_release_slot(cb);
if (!rpc_restart_call(task))
goto out;
--
Jeff Layton <jlayton@xxxxxxxxxx>
