| Message ID | 20241206004829.3497925-6-neilb@suse.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | nfsd: allocate/free session-based DRC slots on demand | expand |
On Fri, 2024-12-06 at 11:43 +1100, NeilBrown wrote: > Reducing the number of slots in the session slot table requires > confirmation from the client. This patch adds reduce_session_slots() > which starts the process of getting confirmation, but never calls it. > That will come in a later patch. > > Before we can free a slot we need to confirm that the client won't try > to use it again. This involves returning a lower cr_maxrequests in a > SEQUENCE reply and then seeing a ca_maxrequests on the same slot which > is not larger than we limit we are trying to impose. So for each slot > we need to remember that we have sent a reduced cr_maxrequests. > > To achieve this we introduce a concept of request "generations". Each > time we decide to reduce cr_maxrequests we increment the generation > number, and record this when we return the lower cr_maxrequests to the > client. When a slot with the current generation reports a low > ca_maxrequests, we commit to that level and free extra slots. > > We use an 8 bit generation number (64 seems wasteful) and if it cycles > we iterate all slots and reset the generation number to avoid false matches. > > When we free a slot we store the seqid in the slot pointer so that it can > be restored when we reactivate the slot. The RFC can be read as > suggesting that the slot number could restart from one after a slot is > retired and reactivated, but also suggests that retiring slots is not > required. So when we reactive a slot we accept with the next seqid in > sequence, or 1. > > When decoding sa_highest_slotid into maxslots we need to add 1 - this > matches how it is encoded for the reply. > > Signed-off-by: NeilBrown <neilb@suse.de> > --- > fs/nfsd/nfs4state.c | 80 +++++++++++++++++++++++++++++++++++++++------ > fs/nfsd/nfs4xdr.c | 5 +-- > fs/nfsd/state.h | 4 +++ > fs/nfsd/xdr4.h | 2 -- > 4 files changed, 77 insertions(+), 14 deletions(-) > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index ec4468ebbd40..e73668462739 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -1910,17 +1910,54 @@ gen_sessionid(struct nfsd4_session *ses) > #define NFSD_MIN_HDR_SEQ_SZ (24 + 12 + 44) > > static void > -free_session_slots(struct nfsd4_session *ses) > +free_session_slots(struct nfsd4_session *ses, int from) > { > int i; > > - for (i = 0; i < ses->se_fchannel.maxreqs; i++) { > + if (from >= ses->se_fchannel.maxreqs) > + return; > + > + for (i = from; i < ses->se_fchannel.maxreqs; i++) { > struct nfsd4_slot *slot = xa_load(&ses->se_slots, i); > > - xa_erase(&ses->se_slots, i); > + /* > + * Save the seqid in case we reactivate this slot. > + * This will never require a memory allocation so GFP > + * flag is irrelevant > + */ > + xa_store(&ses->se_slots, i, xa_mk_value(slot->sl_seqid), 0); > free_svc_cred(&slot->sl_cred); > kfree(slot); > } > + ses->se_fchannel.maxreqs = from; > + if (ses->se_target_maxslots > from) > + ses->se_target_maxslots = from; > +} > + > +static int __maybe_unused > +reduce_session_slots(struct nfsd4_session *ses, int dec) > +{ > + struct nfsd_net *nn = net_generic(ses->se_client->net, > + nfsd_net_id); > + int ret = 0; > + > + if (ses->se_target_maxslots <= 1) > + return ret; > + if (!spin_trylock(&nn->client_lock)) > + return ret; > + ret = min(dec, ses->se_target_maxslots-1); > + ses->se_target_maxslots -= ret; > + ses->se_slot_gen += 1; > + if (ses->se_slot_gen == 0) { > + int i; > + ses->se_slot_gen = 1; > + for (i = 0; i < ses->se_fchannel.maxreqs; i++) { > + struct nfsd4_slot *slot = xa_load(&ses->se_slots, i); > + slot->sl_generation = 0; > + } > + } > + spin_unlock(&nn->client_lock); > + return ret; > } > > /* > @@ -1968,6 +2005,7 @@ static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fattrs, > } > fattrs->maxreqs = i; > memcpy(&new->se_fchannel, fattrs, sizeof(struct nfsd4_channel_attrs)); > + new->se_target_maxslots = i; > new->se_cb_slot_avail = ~0U; > new->se_cb_highest_slot = min(battrs->maxreqs - 1, > NFSD_BC_SLOT_TABLE_SIZE - 1); > @@ -2081,7 +2119,7 @@ static void nfsd4_del_conns(struct nfsd4_session *s) > > static void __free_session(struct nfsd4_session *ses) > { > - free_session_slots(ses); > + free_session_slots(ses, 0); > xa_destroy(&ses->se_slots); > kfree(ses); > } > @@ -2684,6 +2722,9 @@ static int client_info_show(struct seq_file *m, void *v) > seq_printf(m, "session slots:"); > list_for_each_entry(ses, &clp->cl_sessions, se_perclnt) > seq_printf(m, " %u", ses->se_fchannel.maxreqs); > + seq_printf(m, "\nsession target slots:"); > + list_for_each_entry(ses, &clp->cl_sessions, se_perclnt) > + seq_printf(m, " %u", ses->se_target_maxslots); > spin_unlock(&clp->cl_lock); > seq_puts(m, "\n"); > > @@ -3674,10 +3715,10 @@ nfsd4_exchange_id_release(union nfsd4_op_u *u) > kfree(exid->server_impl_name); > } > > -static __be32 check_slot_seqid(u32 seqid, u32 slot_seqid, bool slot_inuse) > +static __be32 check_slot_seqid(u32 seqid, u32 slot_seqid, u8 flags) > { > /* The slot is in use, and no response has been sent. */ > - if (slot_inuse) { > + if (flags & NFSD4_SLOT_INUSE) { > if (seqid == slot_seqid) > return nfserr_jukebox; > else > @@ -3686,6 +3727,8 @@ static __be32 check_slot_seqid(u32 seqid, u32 slot_seqid, bool slot_inuse) > /* Note unsigned 32-bit arithmetic handles wraparound: */ > if (likely(seqid == slot_seqid + 1)) > return nfs_ok; > + if ((flags & NFSD4_SLOT_REUSED) && seqid == 1) > + return nfs_ok; > if (seqid == slot_seqid) > return nfserr_replay_cache; > return nfserr_seq_misordered; > @@ -4236,8 +4279,7 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > dprintk("%s: slotid %d\n", __func__, seq->slotid); > > trace_nfsd_slot_seqid_sequence(clp, seq, slot); > - status = check_slot_seqid(seq->seqid, slot->sl_seqid, > - slot->sl_flags & NFSD4_SLOT_INUSE); > + status = check_slot_seqid(seq->seqid, slot->sl_seqid, slot->sl_flags); > if (status == nfserr_replay_cache) { > status = nfserr_seq_misordered; > if (!(slot->sl_flags & NFSD4_SLOT_INITIALIZED)) > @@ -4262,6 +4304,12 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > if (status) > goto out_put_session; > > + if (session->se_target_maxslots < session->se_fchannel.maxreqs && > + slot->sl_generation == session->se_slot_gen && > + seq->maxslots <= session->se_target_maxslots) > + /* Client acknowledged our reduce maxreqs */ > + free_session_slots(session, session->se_target_maxslots); > + > buflen = (seq->cachethis) ? > session->se_fchannel.maxresp_cached : > session->se_fchannel.maxresp_sz; > @@ -4272,9 +4320,11 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > svc_reserve(rqstp, buflen); > > status = nfs_ok; > - /* Success! bump slot seqid */ > + /* Success! accept new slot seqid */ > slot->sl_seqid = seq->seqid; > + slot->sl_flags &= ~NFSD4_SLOT_REUSED; > slot->sl_flags |= NFSD4_SLOT_INUSE; > + slot->sl_generation = session->se_slot_gen; > if (seq->cachethis) > slot->sl_flags |= NFSD4_SLOT_CACHETHIS; > else > @@ -4291,9 +4341,11 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > * the client might use. > */ > if (seq->slotid == session->se_fchannel.maxreqs - 1 && > + session->se_target_maxslots >= session->se_fchannel.maxreqs && > session->se_fchannel.maxreqs < NFSD_MAX_SLOTS_PER_SESSION) { > int s = session->se_fchannel.maxreqs; > int cnt = DIV_ROUND_UP(s, 5); > + void *prev_slot; > > do { > /* > @@ -4307,17 +4359,25 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > */ > slot = kzalloc(slot_bytes(&session->se_fchannel), > GFP_NOWAIT); > + prev_slot = xa_load(&session->se_slots, s); > + if (xa_is_value(prev_slot) && slot) { > + slot->sl_seqid = xa_to_value(prev_slot); > + slot->sl_flags |= NFSD4_SLOT_REUSED; > + } > if (slot && > !xa_is_err(xa_store(&session->se_slots, s, slot, > GFP_ATOMIC | __GFP_NOWARN))) { > s += 1; > session->se_fchannel.maxreqs = s; > + session->se_target_maxslots = s; > } else { > kfree(slot); > + slot = NULL; > } > } while (slot && --cnt > 0); > } > - seq->maxslots = session->se_fchannel.maxreqs; > + seq->maxslots = max(session->se_target_maxslots, seq->maxslots); > + seq->target_maxslots = session->se_target_maxslots; > > out: > switch (clp->cl_cb_state) { > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c > index 53fac037611c..4dcb03cd9292 100644 > --- a/fs/nfsd/nfs4xdr.c > +++ b/fs/nfsd/nfs4xdr.c > @@ -1884,7 +1884,8 @@ nfsd4_decode_sequence(struct nfsd4_compoundargs *argp, > return nfserr_bad_xdr; > seq->seqid = be32_to_cpup(p++); > seq->slotid = be32_to_cpup(p++); > - seq->maxslots = be32_to_cpup(p++); > + /* sa_highest_slotid counts from 0 but maxslots counts from 1 ... */ > + seq->maxslots = be32_to_cpup(p++) + 1; > seq->cachethis = be32_to_cpup(p); > > seq->status_flags = 0; > @@ -4968,7 +4969,7 @@ nfsd4_encode_sequence(struct nfsd4_compoundres *resp, __be32 nfserr, > if (nfserr != nfs_ok) > return nfserr; > /* sr_target_highest_slotid */ > - nfserr = nfsd4_encode_slotid4(xdr, seq->maxslots - 1); > + nfserr = nfsd4_encode_slotid4(xdr, seq->target_maxslots - 1); > if (nfserr != nfs_ok) > return nfserr; > /* sr_status_flags */ > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > index aad547d3ad8b..74f2ab3c95aa 100644 > --- a/fs/nfsd/state.h > +++ b/fs/nfsd/state.h > @@ -249,7 +249,9 @@ struct nfsd4_slot { > #define NFSD4_SLOT_CACHETHIS (1 << 1) > #define NFSD4_SLOT_INITIALIZED (1 << 2) > #define NFSD4_SLOT_CACHED (1 << 3) > +#define NFSD4_SLOT_REUSED (1 << 4) > u8 sl_flags; > + u8 sl_generation; > char sl_data[]; > }; > > @@ -331,6 +333,8 @@ struct nfsd4_session { > struct list_head se_conns; > u32 se_cb_seq_nr[NFSD_BC_SLOT_TABLE_SIZE]; > struct xarray se_slots; /* forward channel slots */ > + u8 se_slot_gen; > + u32 se_target_maxslots; > }; > > /* formatted contents of nfs4_sessionid */ > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > index 382cc1389396..c26ba86dbdfd 100644 > --- a/fs/nfsd/xdr4.h > +++ b/fs/nfsd/xdr4.h > @@ -576,9 +576,7 @@ struct nfsd4_sequence { > u32 slotid; /* request/response */ > u32 maxslots; /* request/response */ > u32 cachethis; /* request */ > -#if 0 > u32 target_maxslots; /* response */ > -#endif /* not yet */ > u32 status_flags; /* response */ > }; > I don't see where the above "#if 0" gets removed in patch 6. Shouldn't it be? While it makes for a larger patch, I think we'd be better served by squashing 5 and 6 together. It doesn't make sense to add this core infrastructure without something to call it.
On Fri, 06 Dec 2024, Jeff Layton wrote: > On Fri, 2024-12-06 at 11:43 +1100, NeilBrown wrote: > > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > > index 382cc1389396..c26ba86dbdfd 100644 > > --- a/fs/nfsd/xdr4.h > > +++ b/fs/nfsd/xdr4.h > > @@ -576,9 +576,7 @@ struct nfsd4_sequence { > > u32 slotid; /* request/response */ > > u32 maxslots; /* request/response */ > > u32 cachethis; /* request */ > > -#if 0 > > u32 target_maxslots; /* response */ > > -#endif /* not yet */ > > u32 status_flags; /* response */ > > }; > > > > > I don't see where the above "#if 0" gets removed in patch 6. Shouldn't > it be? You are misreading. It is being removed here in patch 5. It was added in 2.6.38 in Commit b85d4c01b76f ("nfsd41: sequence operation") > > While it makes for a larger patch, I think we'd be better served by > squashing 5 and 6 together. It doesn't make sense to add this core > infrastructure without something to call it. I find it easier to review if the distinct elements of functionality are kept separate. But if both you and Chuck want just one patch here, I can do that. Thanks, NeilBrown > -- > Jeff Layton <jlayton@kernel.org> >
On Fri, 2024-12-06 at 17:05 +1100, NeilBrown wrote: > On Fri, 06 Dec 2024, Jeff Layton wrote: > > On Fri, 2024-12-06 at 11:43 +1100, NeilBrown wrote: > > > > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > > > index 382cc1389396..c26ba86dbdfd 100644 > > > --- a/fs/nfsd/xdr4.h > > > +++ b/fs/nfsd/xdr4.h > > > @@ -576,9 +576,7 @@ struct nfsd4_sequence { > > > u32 slotid; /* request/response */ > > > u32 maxslots; /* request/response */ > > > u32 cachethis; /* request */ > > > -#if 0 > > > u32 target_maxslots; /* response */ > > > -#endif /* not yet */ > > > u32 status_flags; /* response */ > > > }; > > > > > > > > > I don't see where the above "#if 0" gets removed in patch 6. Shouldn't > > it be? > > You are misreading. It is being removed here in patch 5. > It was added in 2.6.38 in > Commit b85d4c01b76f ("nfsd41: sequence operation") > Oh, sorry -- my mistake. That's what I get for reviewing patches just before boarding a redeye flight! > > > > > While it makes for a larger patch, I think we'd be better served by > > squashing 5 and 6 together. It doesn't make sense to add this core > > infrastructure without something to call it. > > I find it easier to review if the distinct elements of functionality are > kept separate. But if both you and Chuck want just one patch here, I > can do that. > The proposed code is bisectable, so I don't feel too strongly about it. Adding in unused functions is "Not The Way We (Usually) Do Things" though. I think in this case it was harder for me to review, since I had to skip ahead to patch #6 to see how reduce_session_slots() would actually be used. The spin_trylock(), in particular was confusing until I realized it was being called from a shrinker that iterated over all of the clients and spinning there is probably not good. Either way, a kerneldoc header over reduce_session_slots() that explains this subtlety would be nice.
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index ec4468ebbd40..e73668462739 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1910,17 +1910,54 @@ gen_sessionid(struct nfsd4_session *ses) #define NFSD_MIN_HDR_SEQ_SZ (24 + 12 + 44) static void -free_session_slots(struct nfsd4_session *ses) +free_session_slots(struct nfsd4_session *ses, int from) { int i; - for (i = 0; i < ses->se_fchannel.maxreqs; i++) { + if (from >= ses->se_fchannel.maxreqs) + return; + + for (i = from; i < ses->se_fchannel.maxreqs; i++) { struct nfsd4_slot *slot = xa_load(&ses->se_slots, i); - xa_erase(&ses->se_slots, i); + /* + * Save the seqid in case we reactivate this slot. + * This will never require a memory allocation so GFP + * flag is irrelevant + */ + xa_store(&ses->se_slots, i, xa_mk_value(slot->sl_seqid), 0); free_svc_cred(&slot->sl_cred); kfree(slot); } + ses->se_fchannel.maxreqs = from; + if (ses->se_target_maxslots > from) + ses->se_target_maxslots = from; +} + +static int __maybe_unused +reduce_session_slots(struct nfsd4_session *ses, int dec) +{ + struct nfsd_net *nn = net_generic(ses->se_client->net, + nfsd_net_id); + int ret = 0; + + if (ses->se_target_maxslots <= 1) + return ret; + if (!spin_trylock(&nn->client_lock)) + return ret; + ret = min(dec, ses->se_target_maxslots-1); + ses->se_target_maxslots -= ret; + ses->se_slot_gen += 1; + if (ses->se_slot_gen == 0) { + int i; + ses->se_slot_gen = 1; + for (i = 0; i < ses->se_fchannel.maxreqs; i++) { + struct nfsd4_slot *slot = xa_load(&ses->se_slots, i); + slot->sl_generation = 0; + } + } + spin_unlock(&nn->client_lock); + return ret; } /* @@ -1968,6 +2005,7 @@ static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fattrs, } fattrs->maxreqs = i; memcpy(&new->se_fchannel, fattrs, sizeof(struct nfsd4_channel_attrs)); + new->se_target_maxslots = i; new->se_cb_slot_avail = ~0U; new->se_cb_highest_slot = min(battrs->maxreqs - 1, NFSD_BC_SLOT_TABLE_SIZE - 1); @@ -2081,7 +2119,7 @@ static void nfsd4_del_conns(struct nfsd4_session *s) static void __free_session(struct nfsd4_session *ses) { - free_session_slots(ses); + free_session_slots(ses, 0); xa_destroy(&ses->se_slots); kfree(ses); } @@ -2684,6 +2722,9 @@ static int client_info_show(struct seq_file *m, void *v) seq_printf(m, "session slots:"); list_for_each_entry(ses, &clp->cl_sessions, se_perclnt) seq_printf(m, " %u", ses->se_fchannel.maxreqs); + seq_printf(m, "\nsession target slots:"); + list_for_each_entry(ses, &clp->cl_sessions, se_perclnt) + seq_printf(m, " %u", ses->se_target_maxslots); spin_unlock(&clp->cl_lock); seq_puts(m, "\n"); @@ -3674,10 +3715,10 @@ nfsd4_exchange_id_release(union nfsd4_op_u *u) kfree(exid->server_impl_name); } -static __be32 check_slot_seqid(u32 seqid, u32 slot_seqid, bool slot_inuse) +static __be32 check_slot_seqid(u32 seqid, u32 slot_seqid, u8 flags) { /* The slot is in use, and no response has been sent. */ - if (slot_inuse) { + if (flags & NFSD4_SLOT_INUSE) { if (seqid == slot_seqid) return nfserr_jukebox; else @@ -3686,6 +3727,8 @@ static __be32 check_slot_seqid(u32 seqid, u32 slot_seqid, bool slot_inuse) /* Note unsigned 32-bit arithmetic handles wraparound: */ if (likely(seqid == slot_seqid + 1)) return nfs_ok; + if ((flags & NFSD4_SLOT_REUSED) && seqid == 1) + return nfs_ok; if (seqid == slot_seqid) return nfserr_replay_cache; return nfserr_seq_misordered; @@ -4236,8 +4279,7 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, dprintk("%s: slotid %d\n", __func__, seq->slotid); trace_nfsd_slot_seqid_sequence(clp, seq, slot); - status = check_slot_seqid(seq->seqid, slot->sl_seqid, - slot->sl_flags & NFSD4_SLOT_INUSE); + status = check_slot_seqid(seq->seqid, slot->sl_seqid, slot->sl_flags); if (status == nfserr_replay_cache) { status = nfserr_seq_misordered; if (!(slot->sl_flags & NFSD4_SLOT_INITIALIZED)) @@ -4262,6 +4304,12 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, if (status) goto out_put_session; + if (session->se_target_maxslots < session->se_fchannel.maxreqs && + slot->sl_generation == session->se_slot_gen && + seq->maxslots <= session->se_target_maxslots) + /* Client acknowledged our reduce maxreqs */ + free_session_slots(session, session->se_target_maxslots); + buflen = (seq->cachethis) ? session->se_fchannel.maxresp_cached : session->se_fchannel.maxresp_sz; @@ -4272,9 +4320,11 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, svc_reserve(rqstp, buflen); status = nfs_ok; - /* Success! bump slot seqid */ + /* Success! accept new slot seqid */ slot->sl_seqid = seq->seqid; + slot->sl_flags &= ~NFSD4_SLOT_REUSED; slot->sl_flags |= NFSD4_SLOT_INUSE; + slot->sl_generation = session->se_slot_gen; if (seq->cachethis) slot->sl_flags |= NFSD4_SLOT_CACHETHIS; else @@ -4291,9 +4341,11 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, * the client might use. */ if (seq->slotid == session->se_fchannel.maxreqs - 1 && + session->se_target_maxslots >= session->se_fchannel.maxreqs && session->se_fchannel.maxreqs < NFSD_MAX_SLOTS_PER_SESSION) { int s = session->se_fchannel.maxreqs; int cnt = DIV_ROUND_UP(s, 5); + void *prev_slot; do { /* @@ -4307,17 +4359,25 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, */ slot = kzalloc(slot_bytes(&session->se_fchannel), GFP_NOWAIT); + prev_slot = xa_load(&session->se_slots, s); + if (xa_is_value(prev_slot) && slot) { + slot->sl_seqid = xa_to_value(prev_slot); + slot->sl_flags |= NFSD4_SLOT_REUSED; + } if (slot && !xa_is_err(xa_store(&session->se_slots, s, slot, GFP_ATOMIC | __GFP_NOWARN))) { s += 1; session->se_fchannel.maxreqs = s; + session->se_target_maxslots = s; } else { kfree(slot); + slot = NULL; } } while (slot && --cnt > 0); } - seq->maxslots = session->se_fchannel.maxreqs; + seq->maxslots = max(session->se_target_maxslots, seq->maxslots); + seq->target_maxslots = session->se_target_maxslots; out: switch (clp->cl_cb_state) { diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 53fac037611c..4dcb03cd9292 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -1884,7 +1884,8 @@ nfsd4_decode_sequence(struct nfsd4_compoundargs *argp, return nfserr_bad_xdr; seq->seqid = be32_to_cpup(p++); seq->slotid = be32_to_cpup(p++); - seq->maxslots = be32_to_cpup(p++); + /* sa_highest_slotid counts from 0 but maxslots counts from 1 ... */ + seq->maxslots = be32_to_cpup(p++) + 1; seq->cachethis = be32_to_cpup(p); seq->status_flags = 0; @@ -4968,7 +4969,7 @@ nfsd4_encode_sequence(struct nfsd4_compoundres *resp, __be32 nfserr, if (nfserr != nfs_ok) return nfserr; /* sr_target_highest_slotid */ - nfserr = nfsd4_encode_slotid4(xdr, seq->maxslots - 1); + nfserr = nfsd4_encode_slotid4(xdr, seq->target_maxslots - 1); if (nfserr != nfs_ok) return nfserr; /* sr_status_flags */ diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index aad547d3ad8b..74f2ab3c95aa 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -249,7 +249,9 @@ struct nfsd4_slot { #define NFSD4_SLOT_CACHETHIS (1 << 1) #define NFSD4_SLOT_INITIALIZED (1 << 2) #define NFSD4_SLOT_CACHED (1 << 3) +#define NFSD4_SLOT_REUSED (1 << 4) u8 sl_flags; + u8 sl_generation; char sl_data[]; }; @@ -331,6 +333,8 @@ struct nfsd4_session { struct list_head se_conns; u32 se_cb_seq_nr[NFSD_BC_SLOT_TABLE_SIZE]; struct xarray se_slots; /* forward channel slots */ + u8 se_slot_gen; + u32 se_target_maxslots; }; /* formatted contents of nfs4_sessionid */ diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h index 382cc1389396..c26ba86dbdfd 100644 --- a/fs/nfsd/xdr4.h +++ b/fs/nfsd/xdr4.h @@ -576,9 +576,7 @@ struct nfsd4_sequence { u32 slotid; /* request/response */ u32 maxslots; /* request/response */ u32 cachethis; /* request */ -#if 0 u32 target_maxslots; /* response */ -#endif /* not yet */ u32 status_flags; /* response */ };
Reducing the number of slots in the session slot table requires confirmation from the client. This patch adds reduce_session_slots() which starts the process of getting confirmation, but never calls it. That will come in a later patch. Before we can free a slot we need to confirm that the client won't try to use it again. This involves returning a lower cr_maxrequests in a SEQUENCE reply and then seeing a ca_maxrequests on the same slot which is not larger than we limit we are trying to impose. So for each slot we need to remember that we have sent a reduced cr_maxrequests. To achieve this we introduce a concept of request "generations". Each time we decide to reduce cr_maxrequests we increment the generation number, and record this when we return the lower cr_maxrequests to the client. When a slot with the current generation reports a low ca_maxrequests, we commit to that level and free extra slots. We use an 8 bit generation number (64 seems wasteful) and if it cycles we iterate all slots and reset the generation number to avoid false matches. When we free a slot we store the seqid in the slot pointer so that it can be restored when we reactivate the slot. The RFC can be read as suggesting that the slot number could restart from one after a slot is retired and reactivated, but also suggests that retiring slots is not required. So when we reactive a slot we accept with the next seqid in sequence, or 1. When decoding sa_highest_slotid into maxslots we need to add 1 - this matches how it is encoded for the reply. Signed-off-by: NeilBrown <neilb@suse.de> --- fs/nfsd/nfs4state.c | 80 +++++++++++++++++++++++++++++++++++++++------ fs/nfsd/nfs4xdr.c | 5 +-- fs/nfsd/state.h | 4 +++ fs/nfsd/xdr4.h | 2 -- 4 files changed, 77 insertions(+), 14 deletions(-)