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 haven't been able to reproduce the cl_revoked list ending non-empty but I have hit it, let's say 2-3times in the 4days that I've been trying various things trying to reproduce it. And thus my attempt at changing the number of callback session slots (and hitting a kernel oops). Still trying. Also another comment is that I don't see having multiple slots help with the issue of having numerous recalls that end up resulting in 6 RPC exchanges I've described earlier. Instead what I see is when the server starts setting the SEQUENCE flag of revocable state, then the CB_RECALLs are getting ERR_DELAY error (not there aren't multiple callbacks in flight, perhaps at most 2). So it seems like things are "slowing down" even further. There are about 2-3 CB_RECALLs 3rd getting the reply then OPEN which gets BAD_STATEID, then TEST_STATEID, FREE_STATEID, and then OPEN. > > --- > > 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> > > > >
