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authorRick Macklem <rmacklem@FreeBSD.org>2021-04-26 23:24:10 +0000
committerRick Macklem <rmacklem@FreeBSD.org>2021-04-26 23:24:10 +0000
commit87597731488105dd1ab921a95e39bb62e1abe668 (patch)
tree0b7f5a2470dda13d09d0520772acaf3226e69c83
parent43bbae19483fbde0a91e61acad8a6e71e334c8b8 (diff)
downloadsrc-87597731488105dd1ab921a95e39bb62e1abe668.tar.gz
src-87597731488105dd1ab921a95e39bb62e1abe668.zip
nfsd: fix the slot sequence# when a callback fails
Commit 4281bfec3628 patched the server so that the callback session slot would be free'd for reuse when a callback attempt fails. However, this can often result in the sequence# for the session slot to be advanced such that the client end will reply NFSERR_SEQMISORDERED. To avoid the NFSERR_SEQMISORDERED client reply, this patch negates the sequence# advance for the case where the callback has failed. The common case is a failed back channel, where the callback cannot be sent to the client, and not advancing the sequence# is correct for this case. For the uncommon case where the client's reply to the callback is lost, not advancing the sequence# will indicate to the client that the next callback is a retry and not a new callback. But, since the FreeBSD server always sets "csa_cachethis" false in the callback sequence operation, a retry and a new callback should be handled the same way by the client, so this should not matter. Until you have this patch in your NFSv4.1/4.2 server, you should consider avoiding the use of delegations. Even with this patch, interoperation with the Linux NFSv4.1/4.2 client in kernel versions prior to 5.3 can result in frequent 15second delays if delegations are enabled. This occurs because, for kernels prior to 5.3, the Linux client does a TCP reconnect every time it sees multiple concurrent callbacks and then it takes 15seconds to recover the back channel after doing so. MFC after: 2 weeks
-rw-r--r--sys/fs/nfs/nfs_commonkrpc.c4
-rw-r--r--sys/fs/nfs/nfs_commonsubs.c4
-rw-r--r--sys/fs/nfs/nfs_var.h2
-rw-r--r--sys/fs/nfsserver/nfs_nfsdstate.c23
4 files changed, 26 insertions, 7 deletions
diff --git a/sys/fs/nfs/nfs_commonkrpc.c b/sys/fs/nfs/nfs_commonkrpc.c
index daf8082fa1c3..6e766abcf4b1 100644
--- a/sys/fs/nfs/nfs_commonkrpc.c
+++ b/sys/fs/nfs/nfs_commonkrpc.c
@@ -871,7 +871,7 @@ tryagain:
sep->nfsess_slotseq[nd->nd_slotid] += 10;
mtx_unlock(&sep->nfsess_mtx);
/* And free the slot. */
- nfsv4_freeslot(sep, nd->nd_slotid);
+ nfsv4_freeslot(sep, nd->nd_slotid, false);
}
NFSINCRGLOBAL(nfsstatsv1.rpcinvalid);
error = ENXIO;
@@ -1108,7 +1108,7 @@ tryagain:
if ((nd->nd_flag & ND_NFSV4) != 0) {
/* Free the slot, as required. */
if (freeslot != -1)
- nfsv4_freeslot(sep, freeslot);
+ nfsv4_freeslot(sep, freeslot, false);
/*
* If this op is Putfh, throw its results away.
*/
diff --git a/sys/fs/nfs/nfs_commonsubs.c b/sys/fs/nfs/nfs_commonsubs.c
index a30ee458e06c..539cbbbde7d2 100644
--- a/sys/fs/nfs/nfs_commonsubs.c
+++ b/sys/fs/nfs/nfs_commonsubs.c
@@ -4811,7 +4811,7 @@ nfsv4_sequencelookup(struct nfsmount *nmp, struct nfsclsession *sep,
* Free a session slot.
*/
void
-nfsv4_freeslot(struct nfsclsession *sep, int slot)
+nfsv4_freeslot(struct nfsclsession *sep, int slot, bool resetseq)
{
uint64_t bitval;
@@ -4819,6 +4819,8 @@ nfsv4_freeslot(struct nfsclsession *sep, int slot)
if (slot > 0)
bitval <<= slot;
mtx_lock(&sep->nfsess_mtx);
+ if (resetseq)
+ sep->nfsess_slotseq[slot]--;
if ((bitval & sep->nfsess_slots) == 0)
printf("freeing free slot!!\n");
sep->nfsess_slots &= ~bitval;
diff --git a/sys/fs/nfs/nfs_var.h b/sys/fs/nfs/nfs_var.h
index 201c5a5fc2b5..f23d56050449 100644
--- a/sys/fs/nfs/nfs_var.h
+++ b/sys/fs/nfs/nfs_var.h
@@ -355,7 +355,7 @@ void nfsv4_setsequence(struct nfsmount *, struct nfsrv_descript *,
struct nfsclsession *, int);
int nfsv4_sequencelookup(struct nfsmount *, struct nfsclsession *, int *,
int *, uint32_t *, uint8_t *);
-void nfsv4_freeslot(struct nfsclsession *, int);
+void nfsv4_freeslot(struct nfsclsession *, int, bool);
struct ucred *nfsrv_getgrpscred(struct ucred *);
struct nfsdevice *nfsv4_findmirror(struct nfsmount *);
void nfsm_set(struct nfsrv_descript *, u_int);
diff --git a/sys/fs/nfsserver/nfs_nfsdstate.c b/sys/fs/nfsserver/nfs_nfsdstate.c
index 430f09844b83..3aebddad0962 100644
--- a/sys/fs/nfsserver/nfs_nfsdstate.c
+++ b/sys/fs/nfsserver/nfs_nfsdstate.c
@@ -4572,7 +4572,8 @@ nfsrv_docallback(struct nfsclient *clp, int procnum, nfsv4stateid_t *stateidp,
if ((clp->lc_flags & LCL_NFSV41) != 0) {
error = ECONNREFUSED;
if (procnum != NFSV4PROC_CBNULL)
- nfsv4_freeslot(&sep->sess_cbsess, slotpos);
+ nfsv4_freeslot(&sep->sess_cbsess, slotpos,
+ true);
nfsrv_freesession(sep, NULL);
} else if (nd->nd_procnum == NFSV4PROC_CBNULL)
error = newnfs_connect(NULL, &clp->lc_req, cred,
@@ -4604,8 +4605,24 @@ nfsrv_docallback(struct nfsclient *clp, int procnum, nfsv4stateid_t *stateidp,
error = ECONNREFUSED;
}
NFSD_DEBUG(4, "aft newnfs_request=%d\n", error);
- if (error != 0 && procnum != NFSV4PROC_CBNULL)
- nfsv4_freeslot(&sep->sess_cbsess, slotpos);
+ if (error != 0 && procnum != NFSV4PROC_CBNULL) {
+ /*
+ * It is likely that the callback was never
+ * processed by the client and, as such,
+ * the sequence# for the session slot needs
+ * to be backed up by one to avoid a
+ * NFSERR_SEQMISORDERED error reply.
+ * For the unlikely case where the callback
+ * was processed by the client, this will
+ * make the next callback on the slot
+ * appear to be a retry.
+ * Since callbacks never specify that the
+ * reply be cached, this "apparent retry"
+ * should not be a problem.
+ */
+ nfsv4_freeslot(&sep->sess_cbsess, slotpos,
+ true);
+ }
nfsrv_freesession(sep, NULL);
} else
error = newnfs_request(nd, NULL, clp, &clp->lc_req,