On Wed, Nov 6, 2024 at 11:44 AM Olga Kornievskaia <aglo@xxxxxxxxx> wrote: > > On Tue, Nov 5, 2024 at 7:31 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > > nfsd currently only uses a single slot in the callback channel, which is > > proving to be a bottleneck in some cases. Widen the callback channel to > > a max of 32 slots (subject to the client's target_maxreqs value). > > > > Change the cb_holds_slot boolean to an integer that tracks the current > > slot number (with -1 meaning "unassigned"). Move the callback slot > > tracking info into the session. Add a new u32 that acts as a bitmap to > > track which slots are in use, and a u32 to track the latest callback > > target_slotid that the client reports. To protect the new fields, add > > a new per-session spinlock (the se_lock). Fix nfsd41_cb_get_slot to always > > search for the lowest slotid (using ffs()). > > > > Finally, convert the session->se_cb_seq_nr field into an array of > > counters and add the necessary handling to ensure that the seqids get > > reset at the appropriate times. > > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > > --- > > v3 has a bug that Olga hit in testing. This version should fix the wait > > when the slot table is full. Olga, if you're able to test this one, it > > would be much appreciated. > > I have tested this version. I can confirm that I'm not seeing the > softlockup. But the server still does not use the lowest available > slot. It is hard for me to describe the algorithm of picking the slot > number (in general it still seems to be picking the next slot value, > even though slots have been replied to). I have seen slot 0 re-used > eventually but it seemed to be when the server came to using slot=13. > > The other unfortunate thing that's happening when I use these patches > is my test case that recalling delegations and making sure that the > state management gets handled properly (ie., the patch that I've > submitted to fix a race between the laundromat thread and free_state) > is not working. After all the recalls, the server still thinks it has > revoked state. I have to debug more to figure out what's going on. I have finally been able to consistently hit the problem and it's not a server issue but I can't decide who's at fault here -- client or server. While handling the fact that state is revoked the client sends what now is a SETATTR (for deleg attributes)+DELEGRETURN (previously just a DELEGRETURN). SETATTR fails with BAD_STATEID. Client doesn't do anything. Previously (before the deleg attr support) client would sent DELEGRETURN and server would fail with DELEG_REVOKED or BAD_STATEID and the client would follow up with FREE_STATEID. But now the client doesn't send a FREE_STATEID and thus the server is left with "revoked state which never was freed". Now, if the server returned DELEG_REVOKED instead of BAD_STATEID for the SETATTR then the problem doesn't happen. Question: is the server incorrect here or is the client incorrect and should have (1) either also resent the delegreturn on its own which was not processed before and that should have still triggered the free_stateid or (2) should have treated bad_stateid error of setattr in the delegreturn compound such that it freed the state there. > > > --- > > Changes in v4: > > - Fix the wait for a slot in nfsd41_cb_get_slot() > > - Link to v3: https://lore.kernel.org/r/20241030-bcwide-v3-0-c2df49a26c45@xxxxxxxxxx > > > > Changes in v3: > > - add patch to convert se_flags to single se_dead bool > > - fix off-by-one bug in handling of NFSD_BC_SLOT_TABLE_MAX > > - don't reject target highest slot value of 0 > > - Link to v2: https://lore.kernel.org/r/20241029-bcwide-v2-1-e9010b6ef55d@xxxxxxxxxx > > > > Changes in v2: > > - take cl_lock when fetching fields from session to be encoded > > - use fls() instead of bespoke highest_unset_index() > > - rename variables in several functions with more descriptive names > > - clamp limit of for loop in update_cb_slot_table() > > - re-add missing rpc_wake_up_queued_task() call > > - fix slotid check in decode_cb_sequence4resok() > > - add new per-session spinlock > > --- > > fs/nfsd/nfs4callback.c | 113 ++++++++++++++++++++++++++++++++++++------------- > > fs/nfsd/nfs4state.c | 11 +++-- > > fs/nfsd/state.h | 15 ++++--- > > fs/nfsd/trace.h | 2 +- > > 4 files changed, 101 insertions(+), 40 deletions(-) > > > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > > index e38fa834b3d91333acf1425eb14c644e5d5f2601..47a678333907eaa92db305dada503704c34c15b2 100644 > > --- a/fs/nfsd/nfs4callback.c > > +++ b/fs/nfsd/nfs4callback.c > > @@ -406,6 +406,19 @@ encode_cb_getattr4args(struct xdr_stream *xdr, struct nfs4_cb_compound_hdr *hdr, > > hdr->nops++; > > } > > > > +static u32 highest_slotid(struct nfsd4_session *ses) > > +{ > > + u32 idx; > > + > > + spin_lock(&ses->se_lock); > > + idx = fls(~ses->se_cb_slot_avail); > > + if (idx > 0) > > + --idx; > > + idx = max(idx, ses->se_cb_highest_slot); > > + spin_unlock(&ses->se_lock); > > + return idx; > > +} > > + > > /* > > * CB_SEQUENCE4args > > * > > @@ -432,15 +445,35 @@ static void encode_cb_sequence4args(struct xdr_stream *xdr, > > encode_sessionid4(xdr, session); > > > > p = xdr_reserve_space(xdr, 4 + 4 + 4 + 4 + 4); > > - *p++ = cpu_to_be32(session->se_cb_seq_nr); /* csa_sequenceid */ > > - *p++ = xdr_zero; /* csa_slotid */ > > - *p++ = xdr_zero; /* csa_highest_slotid */ > > + *p++ = cpu_to_be32(session->se_cb_seq_nr[cb->cb_held_slot]); /* csa_sequenceid */ > > + *p++ = cpu_to_be32(cb->cb_held_slot); /* csa_slotid */ > > + *p++ = cpu_to_be32(highest_slotid(session)); /* csa_highest_slotid */ > > *p++ = xdr_zero; /* csa_cachethis */ > > xdr_encode_empty_array(p); /* csa_referring_call_lists */ > > > > hdr->nops++; > > } > > > > +static void update_cb_slot_table(struct nfsd4_session *ses, u32 target) > > +{ > > + /* No need to do anything if nothing changed */ > > + if (likely(target == READ_ONCE(ses->se_cb_highest_slot))) > > + return; > > + > > + spin_lock(&ses->se_lock); > > + if (target > ses->se_cb_highest_slot) { > > + int i; > > + > > + target = min(target, NFSD_BC_SLOT_TABLE_MAX); > > + > > + /* Growing the slot table. Reset any new sequences to 1 */ > > + for (i = ses->se_cb_highest_slot + 1; i <= target; ++i) > > + ses->se_cb_seq_nr[i] = 1; > > + } > > + ses->se_cb_highest_slot = target; > > + spin_unlock(&ses->se_lock); > > +} > > + > > /* > > * CB_SEQUENCE4resok > > * > > @@ -468,7 +501,7 @@ static int decode_cb_sequence4resok(struct xdr_stream *xdr, > > struct nfsd4_session *session = cb->cb_clp->cl_cb_session; > > int status = -ESERVERFAULT; > > __be32 *p; > > - u32 dummy; > > + u32 seqid, slotid, target; > > > > /* > > * If the server returns different values for sessionID, slotID or > > @@ -484,21 +517,22 @@ static int decode_cb_sequence4resok(struct xdr_stream *xdr, > > } > > p += XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN); > > > > - dummy = be32_to_cpup(p++); > > - if (dummy != session->se_cb_seq_nr) { > > + seqid = be32_to_cpup(p++); > > + if (seqid != session->se_cb_seq_nr[cb->cb_held_slot]) { > > dprintk("NFS: %s Invalid sequence number\n", __func__); > > goto out; > > } > > > > - dummy = be32_to_cpup(p++); > > - if (dummy != 0) { > > + slotid = be32_to_cpup(p++); > > + if (slotid != cb->cb_held_slot) { > > dprintk("NFS: %s Invalid slotid\n", __func__); > > goto out; > > } > > > > - /* > > - * FIXME: process highest slotid and target highest slotid > > - */ > > + p++; // ignore current highest slot value > > + > > + target = be32_to_cpup(p++); > > + update_cb_slot_table(session, target); > > status = 0; > > out: > > cb->cb_seq_status = status; > > @@ -1203,6 +1237,22 @@ void nfsd4_change_callback(struct nfs4_client *clp, struct nfs4_cb_conn *conn) > > spin_unlock(&clp->cl_lock); > > } > > > > +static int grab_slot(struct nfsd4_session *ses) > > +{ > > + int idx; > > + > > + spin_lock(&ses->se_lock); > > + idx = ffs(ses->se_cb_slot_avail) - 1; > > + if (idx < 0 || idx > ses->se_cb_highest_slot) { > > + spin_unlock(&ses->se_lock); > > + return -1; > > + } > > + /* clear the bit for the slot */ > > + ses->se_cb_slot_avail &= ~BIT(idx); > > + spin_unlock(&ses->se_lock); > > + return idx; > > +} > > + > > /* > > * There's currently a single callback channel slot. > > * If the slot is available, then mark it busy. Otherwise, set the > > @@ -1211,28 +1261,32 @@ void nfsd4_change_callback(struct nfs4_client *clp, struct nfs4_cb_conn *conn) > > static bool nfsd41_cb_get_slot(struct nfsd4_callback *cb, struct rpc_task *task) > > { > > struct nfs4_client *clp = cb->cb_clp; > > + struct nfsd4_session *ses = clp->cl_cb_session; > > > > - if (!cb->cb_holds_slot && > > - test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) { > > + if (cb->cb_held_slot >= 0) > > + return true; > > + cb->cb_held_slot = grab_slot(ses); > > + if (cb->cb_held_slot < 0) { > > rpc_sleep_on(&clp->cl_cb_waitq, task, NULL); > > /* Race breaker */ > > - if (test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) { > > - dprintk("%s slot is busy\n", __func__); > > + cb->cb_held_slot = grab_slot(ses); > > + if (cb->cb_held_slot < 0) > > return false; > > - } > > rpc_wake_up_queued_task(&clp->cl_cb_waitq, task); > > } > > - cb->cb_holds_slot = true; > > return true; > > } > > > > static void nfsd41_cb_release_slot(struct nfsd4_callback *cb) > > { > > struct nfs4_client *clp = cb->cb_clp; > > + struct nfsd4_session *ses = clp->cl_cb_session; > > > > - if (cb->cb_holds_slot) { > > - cb->cb_holds_slot = false; > > - clear_bit(0, &clp->cl_cb_slot_busy); > > + if (cb->cb_held_slot >= 0) { > > + spin_lock(&ses->se_lock); > > + ses->se_cb_slot_avail |= BIT(cb->cb_held_slot); > > + spin_unlock(&ses->se_lock); > > + cb->cb_held_slot = -1; > > rpc_wake_up_next(&clp->cl_cb_waitq); > > } > > } > > @@ -1249,8 +1303,8 @@ static void nfsd41_destroy_cb(struct nfsd4_callback *cb) > > } > > > > /* > > - * TODO: cb_sequence should support referring call lists, cachethis, multiple > > - * slots, and mark callback channel down on communication errors. > > + * TODO: cb_sequence should support referring call lists, cachethis, > > + * and mark callback channel down on communication errors. > > */ > > static void nfsd4_cb_prepare(struct rpc_task *task, void *calldata) > > { > > @@ -1292,7 +1346,7 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback > > return true; > > } > > > > - if (!cb->cb_holds_slot) > > + if (cb->cb_held_slot < 0) > > goto need_restart; > > > > /* This is the operation status code for CB_SEQUENCE */ > > @@ -1306,10 +1360,10 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback > > * If CB_SEQUENCE returns an error, then the state of the slot > > * (sequence ID, cached reply) MUST NOT change. > > */ > > - ++session->se_cb_seq_nr; > > + ++session->se_cb_seq_nr[cb->cb_held_slot]; > > break; > > case -ESERVERFAULT: > > - ++session->se_cb_seq_nr; > > + ++session->se_cb_seq_nr[cb->cb_held_slot]; > > nfsd4_mark_cb_fault(cb->cb_clp); > > ret = false; > > break; > > @@ -1335,17 +1389,16 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback > > case -NFS4ERR_BADSLOT: > > goto retry_nowait; > > case -NFS4ERR_SEQ_MISORDERED: > > - if (session->se_cb_seq_nr != 1) { > > - session->se_cb_seq_nr = 1; > > + if (session->se_cb_seq_nr[cb->cb_held_slot] != 1) { > > + session->se_cb_seq_nr[cb->cb_held_slot] = 1; > > goto retry_nowait; > > } > > break; > > default: > > nfsd4_mark_cb_fault(cb->cb_clp); > > } > > - nfsd41_cb_release_slot(cb); > > - > > trace_nfsd_cb_free_slot(task, cb); > > + nfsd41_cb_release_slot(cb); > > > > if (RPC_SIGNALLED(task)) > > goto need_restart; > > @@ -1565,7 +1618,7 @@ void nfsd4_init_cb(struct nfsd4_callback *cb, struct nfs4_client *clp, > > INIT_WORK(&cb->cb_work, nfsd4_run_cb_work); > > cb->cb_status = 0; > > cb->cb_need_restart = false; > > - cb->cb_holds_slot = false; > > + cb->cb_held_slot = -1; > > } > > > > /** > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > index baf7994131fe1b0a4715174ba943fd2a9882aa12..75557e7cc9265517f51952563beaa4cfe8adcc3f 100644 > > --- a/fs/nfsd/nfs4state.c > > +++ b/fs/nfsd/nfs4state.c > > @@ -2002,6 +2002,9 @@ static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fattrs, > > } > > > > memcpy(&new->se_fchannel, fattrs, sizeof(struct nfsd4_channel_attrs)); > > + new->se_cb_slot_avail = ~0U; > > + new->se_cb_highest_slot = battrs->maxreqs - 1; > > + spin_lock_init(&new->se_lock); > > return new; > > out_free: > > while (i--) > > @@ -2132,11 +2135,14 @@ static void init_session(struct svc_rqst *rqstp, struct nfsd4_session *new, stru > > > > INIT_LIST_HEAD(&new->se_conns); > > > > - new->se_cb_seq_nr = 1; > > + atomic_set(&new->se_ref, 0); > > new->se_dead = false; > > new->se_cb_prog = cses->callback_prog; > > new->se_cb_sec = cses->cb_sec; > > - atomic_set(&new->se_ref, 0); > > + > > + for (idx = 0; idx < NFSD_BC_SLOT_TABLE_MAX; ++idx) > > + new->se_cb_seq_nr[idx] = 1; > > + > > idx = hash_sessionid(&new->se_sessionid); > > list_add(&new->se_hash, &nn->sessionid_hashtbl[idx]); > > spin_lock(&clp->cl_lock); > > @@ -3159,7 +3165,6 @@ static struct nfs4_client *create_client(struct xdr_netobj name, > > kref_init(&clp->cl_nfsdfs.cl_ref); > > nfsd4_init_cb(&clp->cl_cb_null, clp, NULL, NFSPROC4_CLNT_CB_NULL); > > clp->cl_time = ktime_get_boottime_seconds(); > > - clear_bit(0, &clp->cl_cb_slot_busy); > > copy_verf(clp, verf); > > memcpy(&clp->cl_addr, sa, sizeof(struct sockaddr_storage)); > > clp->cl_cb_session = NULL; > > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > > index d22e4f2c9039324a0953a9e15a3c255fb8ee1a44..848d023cb308f0b69916c4ee34b09075708f0de3 100644 > > --- a/fs/nfsd/state.h > > +++ b/fs/nfsd/state.h > > @@ -71,8 +71,8 @@ struct nfsd4_callback { > > struct work_struct cb_work; > > int cb_seq_status; > > int cb_status; > > + int cb_held_slot; > > bool cb_need_restart; > > - bool cb_holds_slot; > > }; > > > > struct nfsd4_callback_ops { > > @@ -307,6 +307,9 @@ struct nfsd4_conn { > > unsigned char cn_flags; > > }; > > > > +/* Highest slot index that nfsd implements in NFSv4.1+ backchannel */ > > +#define NFSD_BC_SLOT_TABLE_MAX (sizeof(u32) * 8 - 1) > > + > > /* > > * Representation of a v4.1+ session. These are refcounted in a similar fashion > > * to the nfs4_client. References are only taken when the server is actively > > @@ -314,6 +317,10 @@ struct nfsd4_conn { > > */ > > struct nfsd4_session { > > atomic_t se_ref; > > + spinlock_t se_lock; > > + u32 se_cb_slot_avail; /* bitmap of available slots */ > > + u32 se_cb_highest_slot; /* highest slot client wants */ > > + u32 se_cb_prog; > > bool se_dead; > > struct list_head se_hash; /* hash by sessionid */ > > struct list_head se_perclnt; > > @@ -322,8 +329,7 @@ struct nfsd4_session { > > struct nfsd4_channel_attrs se_fchannel; > > struct nfsd4_cb_sec se_cb_sec; > > struct list_head se_conns; > > - u32 se_cb_prog; > > - u32 se_cb_seq_nr; > > + u32 se_cb_seq_nr[NFSD_BC_SLOT_TABLE_MAX + 1]; > > struct nfsd4_slot *se_slots[]; /* forward channel slots */ > > }; > > > > @@ -457,9 +463,6 @@ struct nfs4_client { > > */ > > struct dentry *cl_nfsd_info_dentry; > > > > - /* for nfs41 callbacks */ > > - /* We currently support a single back channel with a single slot */ > > - unsigned long cl_cb_slot_busy; > > struct rpc_wait_queue cl_cb_waitq; /* backchannel callers may */ > > /* wait here for slots */ > > struct net *net; > > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h > > index f318898cfc31614b5a84a4867e18c2b3a07122c9..a9c17186b6892f1df8d7f7b90e250c2913ab23fe 100644 > > --- a/fs/nfsd/trace.h > > +++ b/fs/nfsd/trace.h > > @@ -1697,7 +1697,7 @@ TRACE_EVENT(nfsd_cb_free_slot, > > __entry->cl_id = sid->clientid.cl_id; > > __entry->seqno = sid->sequence; > > __entry->reserved = sid->reserved; > > - __entry->slot_seqno = session->se_cb_seq_nr; > > + __entry->slot_seqno = session->se_cb_seq_nr[cb->cb_held_slot]; > > ), > > TP_printk(SUNRPC_TRACE_TASK_SPECIFIER > > " sessionid=%08x:%08x:%08x:%08x new slot seqno=%u", > > > > --- > > base-commit: 3c16aac09d20f9005fbb0e737b3ec520bbb5badd > > change-id: 20241025-bcwide-6bd7e4b63db2 > > > > Best regards, > > -- > > Jeff Layton <jlayton@xxxxxxxxxx> > > > >
