fs/nfsd/nfs4callback.c | 118 ++++++++++++++++++++++++++++++++++++------------- fs/nfsd/nfs4state.c | 14 ++++-- fs/nfsd/state.h | 15 ++++--- fs/nfsd/trace.h | 2 +- 4 files changed, 109 insertions(+), 40 deletions(-)
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
ints and add the necessary handling to ensure that the seqids get
reset when the slot table grows after shrinking.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
A minor bugfix, and some comments, cleanup and symbol renaming.
---
Changes in v5:
- Fix off-by-one bug when initializing seqid array
- Rename NFSD_BC_SLOT_TABLE_MAX to NFSD_BC_SLOT_TABLE_SIZE, and reframe
it to be the size of the array instead of last index.
- Comments around seqid reinitialization when the slot table grows
- Link to v4: https://lore.kernel.org/r/20241105-bcwide-v4-1-48f52ee0fb0c@kernel.org
Changes in v4:
- Wait the correct way for slots to be freed.
- Link to v3: https://lore.kernel.org/r/20241030-bcwide-v3-0-c2df49a26c45@kernel.org
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@kernel.org
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 | 118 ++++++++++++++++++++++++++++++++++++-------------
fs/nfsd/nfs4state.c | 14 ++++--
fs/nfsd/state.h | 15 ++++---
fs/nfsd/trace.h | 2 +-
4 files changed, 109 insertions(+), 40 deletions(-)
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index e38fa834b3d91333acf1425eb14c644e5d5f2601..0d1ebeaca14a40980d08e223cb6598e20c6ce21a 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 +445,40 @@ 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_SIZE - 1);
+
+ /*
+ * Growing the slot table. Reset any new sequences to 1.
+ *
+ * NB: There is some debate about whether the RFC requires this,
+ * but the Linux client expects it.
+ */
+ 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 +506,7 @@ 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 +522,22 @@ 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 +1242,22 @@ 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 +1266,32 @@ 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 +1308,8 @@ 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 +1351,7 @@ 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 +1365,10 @@ 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 +1394,16 @@ 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 +1623,7 @@ 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 2ce6c367e2596cee3f47da6f197120bef4986160..e0daf8b3982cd218ee128bbc0323a1f375e5935a 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2010,6 +2010,10 @@ 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 = min(battrs->maxreqs - 1,
+ NFSD_BC_SLOT_TABLE_SIZE - 1);
+ spin_lock_init(&new->se_lock);
return new;
out_free:
while (i--)
@@ -2140,11 +2144,14 @@ 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_SIZE; ++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);
@@ -3167,7 +3174,6 @@ 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;
@@ -3949,6 +3955,8 @@ nfsd4_create_session(struct svc_rqst *rqstp,
cr_ses->flags &= ~SESSION4_PERSIST;
/* Upshifting from TCP to RDMA is not supported */
cr_ses->flags &= ~SESSION4_RDMA;
+ /* Report the correct number of backchannel slots */
+ cr_ses->back_channel.maxreqs = new->se_cb_highest_slot + 1;
init_session(rqstp, new, conf, cr_ses);
nfsd4_get_session_locked(new);
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 66b7a4df23f93c3cd18537129d94514268e9c326..554041da8593e14987439cb1c152d1a072bd00ad 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 {
@@ -322,6 +322,9 @@ struct nfsd4_conn {
unsigned char cn_flags;
};
+/* Maximum number of slots that nfsd will use in the backchannel */
+#define NFSD_BC_SLOT_TABLE_SIZE (sizeof(u32) * 8)
+
/*
* 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
@@ -329,6 +332,10 @@ 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;
@@ -337,8 +344,7 @@ 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_SIZE];
struct nfsd4_slot *se_slots[]; /* forward channel slots */
};
@@ -472,9 +478,6 @@ 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 6b7bf8129e4910119959e4c97916991671287837..696c89f68a9e68ecf6b2cd78b39abd3e5d7d4d28 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: f055a6cafaea151c2df2a75f31c3ecfaa8b90b9e
change-id: 20241025-bcwide-6bd7e4b63db2
Best regards,
--
Jeff Layton <jlayton@kernel.org>From: Chuck Lever <chuck.lever@oracle.com>
On Mon, 18 Nov 2024 09:54:34 -0500, Jeff Layton 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()).
>
> [...]
Applied to nfsd-next for v6.13, thanks!
[1/1] nfsd: allow for up to 32 callback session slots
commit: a47e0534dc9cc3f9ee7c914cfddd6912855b5d61
--
Chuck Lever
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