Re: [PATCH Version 4 4/7] NFSv4.1: dynamic session slots

Adamson, Andy
2011-12-13T13:41:49Z

On Dec 12, 2011, at 3:13 PM, Benny Halevy wrote:

> On 2011-12-12 21:21, Adamson, Andy wrote:
>>
>> On Dec 11, 2011, at 8:14 AM, Benny Halevy wrote:
>>
>>> Hi Andy,
>>>
>>> I have some minor-ish comments inline below, but the whole
>>> hlist concept looks to me like it might incur pretty high overhead
>>> in cpu and memory caching.
>>
>> You mean the hash lookup?
>>
>
> hash lookup, list traversal, memory fragmentation…

I'll setup some tests. Note that the rpc_rqst, the rpc_slot need to be allocated as well, and that the tcp layer has a fair number of hlist's….

>
>>>
>>> Have you considered simply reallocating the slot table on grow
>>> and maybe on shrink below a certain threshold?
>>>
>>> On 2011-11-09 20:58, andros@netapp.com wrote:
>>>> From: Andy Adamson <andros@netapp.com>
>>>>
>>>> The session fore/backchannel slot tables implementation is changed from a
>>>> static array to an hlist hashed on slotid. Slotid's are values 0..N where N
>>>> is initially negotiated between the client and server via the CREATE_SESSION
>>>> call, and can be dynamically changed by the server during an active session.
>>>>
>>>> When there are no allocated slots (mount), an initial number of session slots
>>>> is allocated equal to the inital number of dynamic rpc_slots
>>>> created upon transport creation (xprt->min_reqs). Slots are then dynamically
>>>> allocated as needed upto the CREATE_SESSION negotiated max_reqs value.
>>>>
>>>> For session reset the session is drained (inactive). The (old) session has
>>>> allocated slot tables which we will reuse. nfs4_reduce_slots_locked is called
>>>> and only reduces the allocated_slots if the new max_reqs negotiated by the
>>>> reset CREATE_SESSION is less than the number of allocated_slots. The resultant
>>>> slot table is then re-initialized.
>>>>
>>>> CB_SLOT_RECALL is changed only in that it now shares code with session
>>>> reset - it also calls nfs4_reduce_slots_locked.
>>>>
>>>> The backchannel uses the new dynamic slot allocator, even though we only
>>>> currently support a single back channel slot.
>>>>
>>>> Signed-off-by: Andy Adamson <andros@netapp.com>
>>>> ---
>>>> fs/nfs/callback_proc.c | 25 +++-
>>>> fs/nfs/internal.h | 2 +
>>>> fs/nfs/nfs4_fs.h | 1 +
>>>> fs/nfs/nfs4proc.c | 297 ++++++++++++++++++++++++++++++++++-----------
>>>> fs/nfs/nfs4state.c | 12 +--
>>>> fs/nfs/nfs4xdr.c | 20 ++--
>>>> include/linux/nfs_fs_sb.h | 12 +-
>>>> include/linux/nfs_xdr.h | 4 +-
>>>> 8 files changed, 266 insertions(+), 107 deletions(-)
>>>>
>>>> diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
>>>> index 54cea8a..77cc96c 100644
>>>> --- a/fs/nfs/callback_proc.c
>>>> +++ b/fs/nfs/callback_proc.c
>>>> @@ -342,7 +342,7 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
>>>> if (args->csa_slotid >= NFS41_BC_MAX_CALLBACKS)
>>>> return htonl(NFS4ERR_BADSLOT);
>>>>
>>>> - slot = tbl->slots + args->csa_slotid;
>>>> + slot = nfs4_lookup_slot_locked(tbl, args->csa_slotid);
>>>> dprintk("%s slot table seqid: %d\n", __func__, slot->seq_nr);
>>>>
>>>> /* Normal */
>>>> @@ -377,6 +377,22 @@ out_ok:
>>>> return htonl(NFS4_OK);
>>>> }
>>>>
>>>> +static bool test_slot_referring(struct nfs4_slot_table *tbl,
>>>> + struct referring_call *ref)
>>>> +{
>>>> + struct nfs4_slot *slot;
>>>> + bool status = false;
>>>> +
>>>> + spin_lock(&tbl->slot_tbl_lock);
>>>> + if (test_bit(ref->rc_slotid, tbl->used_slots)) {
>>>> + slot = nfs4_lookup_slot_locked(tbl, ref->rc_slotid);
>>>> + if (slot->seq_nr == ref->rc_sequenceid)
>>>> + status = true;
>>>> + }
>>>> + spin_unlock(&tbl->slot_tbl_lock);
>>>> + return status;
>>>> +}
>>>> +
>>>> /*
>>>> * For each referring call triple, check the session's slot table for
>>>> * a match. If the slot is in use and the sequence numbers match, the
>>>> @@ -417,12 +433,7 @@ static bool referring_call_exists(struct nfs_client *clp,
>>>> ((u32 *)&rclist->rcl_sessionid.data)[2],
>>>> ((u32 *)&rclist->rcl_sessionid.data)[3],
>>>> ref->rc_sequenceid, ref->rc_slotid);
>>>> -
>>>> - spin_lock(&tbl->slot_tbl_lock);
>>>> - status = (test_bit(ref->rc_slotid, tbl->used_slots) &&
>>>> - tbl->slots[ref->rc_slotid].seq_nr ==
>>>> - ref->rc_sequenceid);
>>>> - spin_unlock(&tbl->slot_tbl_lock);
>>>> + status = test_slot_referring(tbl, ref);
>>>> if (status)
>>>> goto out;
>>>> }
>>>> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
>>>> index c1a1bd8..4451abf 100644
>>>> --- a/fs/nfs/internal.h
>>>> +++ b/fs/nfs/internal.h
>>>> @@ -354,6 +354,8 @@ extern int _nfs4_call_sync_session(struct rpc_clnt *clnt,
>>>> struct nfs4_sequence_args *args,
>>>> struct nfs4_sequence_res *res,
>>>> int cache_reply);
>>>> +struct nfs4_slot *nfs4_lookup_slot_locked(struct nfs4_slot_table *tbl,
>>>> + u8 slotid);
>>>>
>>>> /*
>>>> * Determine the device name as a string
>>>> diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
>>>> index 693ae22..ff87169 100644
>>>> --- a/fs/nfs/nfs4_fs.h
>>>> +++ b/fs/nfs/nfs4_fs.h
>>>> @@ -242,6 +242,7 @@ extern struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp);
>>>> extern int nfs4_proc_create_session(struct nfs_client *);
>>>> extern int nfs4_proc_destroy_session(struct nfs4_session *);
>>>> extern int nfs4_init_session(struct nfs_server *server);
>>>> +extern void nfs4_reduce_slots_locked(struct nfs4_slot_table *tbl);
>>>> extern int nfs4_proc_get_lease_time(struct nfs_client *clp,
>>>> struct nfs_fsinfo *fsinfo);
>>>> extern int nfs4_proc_layoutcommit(struct nfs4_layoutcommit_data *data,
>>>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>>>> index 2638291..e3a7663 100644
>>>> --- a/fs/nfs/nfs4proc.c
>>>> +++ b/fs/nfs/nfs4proc.c
>>>> @@ -346,6 +346,162 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
>>>> #if defined(CONFIG_NFS_V4_1)
>>>>
>>>> /*
>>>> + * Session dynamic slot table helper functions
>>>> + */
>>>> +
>>>> +static inline u32 slot_tbl_hash(const u8 slotid)
>>>
>>> nit: "const" not really needed here…
>>
>> OK
>>
>>>
>>>> +{
>>>> + return (u32)slotid % SLOT_TABLE_SIZE;
>>>> +}
>>>> +
>>>> +static void nfs4_init_slot(struct nfs4_slot *new, u8 slotid, int ivalue)
>>>> +{
>>>> + INIT_HLIST_NODE(&new->slot_node);
>>>> + new->slotid = slotid;
>>>> + new->seq_nr = ivalue;
>>>> +}
>>>> +
>>>> +static void nfs4_insert_slot_locked(struct nfs4_slot_table *tbl,
>>>> + struct nfs4_slot *new)
>>>> +{
>>>> + u32 hash = slot_tbl_hash(new->slotid);
>>>> +
>>>> + hlist_add_head(&new->slot_node, &tbl->slots[hash]);
>>>> + tbl->allocated_slots++;
>>>> +}
>>>> +
>>>> +/*
>>>> + * Allocate a slot for the next slotid (tbl->allocated_slotid)
>>>> + */
>>>> +static int nfs4_alloc_add_slot(struct nfs4_slot_table *tbl,
>>>> + int ivalue, int slotid,
>>>> + gfp_t gfp_flags)
>>>> +{
>>>> + struct nfs4_slot *new;
>>>> + struct rpc_task *task;
>>>> +
>>>> + dprintk("--> %s slotid=%u tbl->allocated_slots=%d\n", __func__,
>>>> + slotid, tbl->allocated_slots);
>>>> + new = kzalloc(sizeof(struct nfs4_slot), gfp_flags);
>>>> + if (!new)
>>>> + return -ENOMEM;
>>>> + /* tbl->allocated_slots holds the next unallocated slotid */
>>>> + nfs4_init_slot(new, slotid, ivalue);
>>>> + spin_lock(&tbl->slot_tbl_lock);
>>>> + if (tbl->allocated_slots != slotid) {
>>>
>>> This condition doesn't seem to be reliable.
>>> What if the slot table shrunk?
>>
>> tbl->allocated_slots is inc'ed/dec'ed under the slot_tbl_lock. If the slot table shrunk it's because nfs4_remove_slots_locked() was called which adjusts the allocated_slots accordingly
>>
>> So I think it is absolutely reliable.
>>
>
> It will detect that for sure.
> I was concerned about the case where the caller tried to allocate
> a new slot, we fail this test but return success (0)
> and the table shrunk. The caller won't find the slot in this case.
> Therefore it seems unreliable to me - maybe better refer to
> the return value as unreliable rather than the test itself.
> I.e. it doesn't really indicate a success for alloc_add'ing the slot.
>
> I see that in the dynamic case, you don't check the return value and return
> -EAGAIN unconditionally and in the static case you just assume any failure
> is due to -ENOMEM (again ignoring the returned status :). It just goes
> to tell you something's fishy about this function's interface to
> the world ;-)

I see your point. Could be a lot cleaner. I'll refactor

Thanks for the review :)

-->Andy
>
> Benny
>
>>>
>>>> + spin_unlock(&tbl->slot_tbl_lock);
>>>> + kfree(new);
>>>> + dprintk("%s slotid %u already allocated\n", __func__,
>>>> + slotid);
>>>> + return 0;
>>>> + }
>>>> + nfs4_insert_slot_locked(tbl, new);
>>>> +
>>>> + /* This only applies to dynamic allocation */
>>>> + task = rpc_wake_up_next(&tbl->slot_tbl_waitq);
>>>> + if (task)
>>>> + dprintk("%s woke up task %5u\n", __func__, task->tk_pid);
>>>> + spin_unlock(&tbl->slot_tbl_lock);
>>>> + return 0;
>>>> +}
>>>> +
>>>> +/*
>>>> + * Allocate the minimal number of slots required by the transport.
>>>> + * Called at session creation.
>>>> + */
>>>> +static int nfs4_prealloc_slots(struct nfs4_slot_table *tbl, int num, int ivalue)
>>>> +{
>>>> + int i;
>>>> +
>>>> + for (i = 0; i < num; i++) {
>>>> + if (nfs4_alloc_add_slot(tbl, ivalue, tbl->allocated_slots,
>>>> + GFP_NOFS) != 0)
>>>> + return -ENOMEM;
>>>
>>> Returning nfs4_alloc_add_slot's status would be more appropriate.
>>
>> OK
>>
>>> How about also freeing 0 to i-1 in the error case?
>>
>> The transport minimum rpc_slots is the minimum number of (dynamic) rpc_slots needed to make progress. It's set to 2 for TCP. We don't want to try and operate when we don't have the minimum number slots.
>>>
>>>> + }
>>>> + return 0;
>>>> +}
>>>> +
>>>> +/*
>>>> + * Allocate the next slotid. If allocation fails, next request will retry.
>>>> + */
>>>> +static void nfs4_dynamic_alloc_slot(struct nfs4_slot_table *tbl, u8 slotid)
>>>> +{
>>>> + if (slotid != tbl->allocated_slots) {
>>>> + dprintk("%s slotid %u already allocated\n", __func__, slotid);
>>>> + return;
>>>> + }
>>>
>>> This is checked again under the lock in nfs4_alloc_add_slot, no?
>>> so if it is not supposed to be a common case (which I don't believe
>>> it is) I'd just forget about this optimization and call the latter
>>> directly.
>>
>> Yeah, I agree.
>>>
>>>> + nfs4_alloc_add_slot(tbl, 1, slotid, GFP_NOWAIT);
>>>> +}
>>>> +
>>>> +/*
>>>> + * Return the slot associated with the slotid returned by nfs4_find_slot.
>>>> + * If the slot is not found, it has not been allocated.
>>>> + */
>>>> +struct nfs4_slot *
>>>> +nfs4_lookup_slot_locked(struct nfs4_slot_table *tbl, u8 slotid)
>>>> +{
>>>> + struct nfs4_slot *sp;
>>>> + struct hlist_node *n;
>>>> + u32 hash = slot_tbl_hash(slotid);
>>>> +
>>>> + hlist_for_each_entry(sp, n, &tbl->slots[hash], slot_node) {
>>>> + if (sp->slotid == slotid)
>>>> + return sp;
>>>> + }
>>>> + return NULL;
>>>> +}
>>>> +
>>>> +static void nfs4_remove_slot_locked(struct nfs4_slot_table *tbl,
>>>> + struct nfs4_slot *slot)
>>>> +{
>>>> + dprintk("--> %s slotid %d\n", __func__, slot->slotid);
>>>> + hlist_del_init(&slot->slot_node);
>>>> + tbl->allocated_slots--;
>>>> + kfree(slot);
>>>> +}
>>>> +
>>>> +static void nfs4_free_all_slots(struct nfs4_slot_table *tbl)
>>>> +{
>>>> + struct nfs4_slot *slotp;
>>>> + int i;
>>>> +
>>>> + spin_lock(&tbl->slot_tbl_lock);
>>>> + for (i = 0; i < SLOT_TABLE_SIZE; i++) {
>>>> + while (!hlist_empty(&tbl->slots[i])) {
>>>> + slotp = hlist_entry(tbl->slots[i].first,
>>>> + struct nfs4_slot, slot_node);
>>>> + nfs4_remove_slot_locked(tbl, slotp);
>>>> + }
>>>> + /* re-initialize hlist_head */
>>>> + tbl->slots[i].first = NULL;
>>>> + }
>>>> + spin_unlock(&tbl->slot_tbl_lock);
>>>> +}
>>>> +
>>>> +/*
>>>> + * Remove num_dec number of contiguous slotids starting from highest
>>>> + * allocated slotid
>>>> + *
>>>> + * Note: set the new tbl->max_slots prior to calling.
>>>> + */
>>>> +void nfs4_reduce_slots_locked(struct nfs4_slot_table *tbl)
>>>> +{
>>>> + struct nfs4_slot *removeme;
>>>> + int i, rm_slotid = tbl->allocated_slots - 1;
>>>> + int num_dec = tbl->allocated_slots - tbl->max_slots;
>>>> +
>>>> + /* Reset of the slot table can make num_dec <= 0 */
>>>> + if (num_dec <= 0)
>>>> + return;
>>>> + for (i = 0; i < num_dec; i++) {
>>>> + removeme = nfs4_lookup_slot_locked(tbl, rm_slotid);
>>>> + BUG_ON(removeme == NULL);
>>>> + nfs4_remove_slot_locked(tbl, removeme);
>>>> + rm_slotid--;
>>>> + }
>>>> +}
>>>> +
>>>> +/*
>>>> * nfs4_free_slot - free a slot and efficiently update slot table.
>>>> *
>>>> * freeing a slot is trivially done by clearing its respective bit
>>>> @@ -390,8 +546,11 @@ static void nfs4_check_drain_fc_complete(struct nfs4_session *ses)
>>>>
>>>> if (!test_bit(NFS4_SESSION_DRAINING, &ses->session_state)) {
>>>> task = rpc_wake_up_next(&ses->fc_slot_table.slot_tbl_waitq);
>>>> - if (task)
>>>> + if (task) {
>>>> rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
>>>> + dprintk("%s woke up task pid %5u\n", __func__,
>>>> + task->tk_pid);
>>>> + }
>>>> return;
>>>> }
>>>>
>>>> @@ -427,7 +586,7 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
>>>> }
>>>>
>>>> spin_lock(&tbl->slot_tbl_lock);
>>>> - nfs4_free_slot(tbl, res->sr_slot - tbl->slots);
>>>> + nfs4_free_slot(tbl, res->sr_slot->slotid);
>>>> nfs4_check_drain_fc_complete(res->sr_session);
>>>> spin_unlock(&tbl->slot_tbl_lock);
>>>> res->sr_slot = NULL;
>>>> @@ -468,10 +627,8 @@ static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *
>>>> * returned NFS4ERR_DELAY as per Section 2.10.6.2
>>>> * of RFC5661.
>>>> */
>>>> - dprintk("%s: slot=%td seq=%d: Operation in progress\n",
>>>> - __func__,
>>>> - res->sr_slot - res->sr_session->fc_slot_table.slots,
>>>> - res->sr_slot->seq_nr);
>>>> + dprintk("%s: slotid=%u seq=%d: Operation in progress\n",
>>>> + __func__, res->sr_slot->slotid, res->sr_slot->seq_nr);
>>>> goto out_retry;
>>>> default:
>>>> /* Just update the slot sequence no. */
>>>> @@ -479,7 +636,8 @@ static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *
>>>> }
>>>> out:
>>>> /* The session may be reset by one of the error handlers. */
>>>> - dprintk("%s: Error %d free the slot \n", __func__, res->sr_status);
>>>> + dprintk("%s: Error %d free the slot for task pid %5u\n", __func__,
>>>> + res->sr_status, task->tk_pid);
>>>> nfs41_sequence_free_slot(res);
>>>> return 1;
>>>> out_retry:
>>>> @@ -540,7 +698,7 @@ int nfs41_setup_sequence(struct nfs4_session *session,
>>>> struct nfs4_slot_table *tbl;
>>>> u8 slotid;
>>>>
>>>> - dprintk("--> %s\n", __func__);
>>>> + dprintk("--> %s task pid %5u\n", __func__, task->tk_pid);
>>>> /* slot already allocated? */
>>>> if (res->sr_slot != NULL)
>>>> return 0;
>>>> @@ -575,12 +733,24 @@ int nfs41_setup_sequence(struct nfs4_session *session,
>>>> dprintk("<-- %s: no free slots\n", __func__);
>>>> return -EAGAIN;
>>>> }
>>>> + slot = nfs4_lookup_slot_locked(tbl, slotid);
>>>> + if (slot == NULL) {
>>>> + /* keep FIFO order */
>>>> + rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
>>>> + rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL);
>>>> + nfs4_free_slot(tbl, slotid);
>>>
>>> why free the slot here?
>>
>> We just grabbed the bit in nfs4_find_slot - which is the "next available lowest slotid". Since we don't actually have a slot because we need to allocate one, we free it here which allows for another request to grab the slot in between the time we give up the lock, allocate a slot, and call wake up to proceed.
>>
>> -->Andy
>>
>>>
>>> Benny
>>>
>>>> + spin_unlock(&tbl->slot_tbl_lock);
>>>> + dprintk("%s task pid %5u sleeping for dynamic slot %d\n",
>>>> + __func__, task->tk_pid, slotid);
>>>> + /* rpc_wakeup_next called upon success by slot allocator */
>>>> + nfs4_dynamic_alloc_slot(tbl, slotid);
>>>> + return -EAGAIN;
>>>> + }
>>>> spin_unlock(&tbl->slot_tbl_lock);
>>>>
>>>> rpc_task_set_priority(task, RPC_PRIORITY_NORMAL);
>>>> - slot = tbl->slots + slotid;
>>>> args->sa_session = session;
>>>> - args->sa_slotid = slotid;
>>>> + args->sa_slot = slot;
>>>> args->sa_cache_this = cache_reply;
>>>>
>>>> dprintk("<-- %s slotid=%d seqid=%d\n", __func__, slotid, slot->seq_nr);
>>>> @@ -613,9 +783,9 @@ int nfs4_setup_sequence(const struct nfs_server *server,
>>>> goto out;
>>>> }
>>>>
>>>> - dprintk("--> %s clp %p session %p sr_slot %td\n",
>>>> + dprintk("--> %s clp %p session %p sr_slotid %d\n",
>>>> __func__, session->clp, session, res->sr_slot ?
>>>> - res->sr_slot - session->fc_slot_table.slots : -1);
>>>> + res->sr_slot->slotid : -1);
>>>>
>>>> ret = nfs41_setup_sequence(session, args, res, cache_reply,
>>>> task);
>>>> @@ -4976,84 +5146,64 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
>>>> }
>>>>
>>>> /*
>>>> - * Reset a slot table
>>>> + * Reset a slot table. Session has been drained and reset with new slot table
>>>> + * parameters from create_session.
>>>> + * Keep all allocated slots that fit into new slot table max_reqs parameter.
>>>> */
>>>> -static int nfs4_reset_slot_table(struct nfs4_slot_table *tbl, u32 max_reqs,
>>>> +static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl, u32 new_max_reqs,
>>>> int ivalue)
>>>> {
>>>> - struct nfs4_slot *new = NULL;
>>>> + struct nfs4_slot *sp;
>>>> + struct hlist_node *n;
>>>> int i;
>>>> - int ret = 0;
>>>> -
>>>> - dprintk("--> %s: max_reqs=%u, tbl->max_slots %d\n", __func__,
>>>> - max_reqs, tbl->max_slots);
>>>>
>>>> - /* Does the newly negotiated max_reqs match the existing slot table? */
>>>> - if (max_reqs != tbl->max_slots) {
>>>> - ret = -ENOMEM;
>>>> - new = kmalloc(max_reqs * sizeof(struct nfs4_slot),
>>>> - GFP_NOFS);
>>>> - if (!new)
>>>> - goto out;
>>>> - ret = 0;
>>>> - kfree(tbl->slots);
>>>> - }
>>>> spin_lock(&tbl->slot_tbl_lock);
>>>> - if (new) {
>>>> - tbl->slots = new;
>>>> - tbl->max_slots = max_reqs;
>>>> + tbl->max_slots = new_max_reqs;
>>>> + nfs4_reduce_slots_locked(tbl);
>>>> + tbl->highest_used_slotid = -1;
>>>> +
>>>> + for (i = 0; i < SLOT_TABLE_SIZE; i++) {
>>>> + hlist_for_each_entry(sp, n, &tbl->slots[i], slot_node)
>>>> + sp->seq_nr = ivalue;
>>>> }
>>>> - for (i = 0; i < tbl->max_slots; ++i)
>>>> - tbl->slots[i].seq_nr = ivalue;
>>>> spin_unlock(&tbl->slot_tbl_lock);
>>>> - dprintk("%s: tbl=%p slots=%p max_slots=%d\n", __func__,
>>>> - tbl, tbl->slots, tbl->max_slots);
>>>> -out:
>>>> - dprintk("<-- %s: return %d\n", __func__, ret);
>>>> - return ret;
>>>> + dprintk("%s: tbl->max_slots=%d tbl->allocated_slots=%d\n",
>>>> + __func__, tbl->max_slots, tbl->allocated_slots);
>>>> + return;
>>>> }
>>>>
>>>> /* Destroy the slot table */
>>>> static void nfs4_destroy_slot_tables(struct nfs4_session *session)
>>>> {
>>>> - if (session->fc_slot_table.slots != NULL) {
>>>> - kfree(session->fc_slot_table.slots);
>>>> - session->fc_slot_table.slots = NULL;
>>>> - }
>>>> - if (session->bc_slot_table.slots != NULL) {
>>>> - kfree(session->bc_slot_table.slots);
>>>> - session->bc_slot_table.slots = NULL;
>>>> - }
>>>> - return;
>>>> + dprintk("--> %s\n", __func__);
>>>> +
>>>> + nfs4_free_all_slots(&session->fc_slot_table);
>>>> + nfs4_free_all_slots(&session->bc_slot_table);
>>>> }
>>>>
>>>> /*
>>>> * Initialize slot table
>>>> */
>>>> static int nfs4_init_slot_table(struct nfs4_slot_table *tbl,
>>>> - int max_slots, int ivalue)
>>>> + int max_slots, int num_prealloc, int ivalue)
>>>> {
>>>> - struct nfs4_slot *slot;
>>>> - int ret = -ENOMEM;
>>>> + int ret;
>>>>
>>>> BUG_ON(max_slots > NFS4_MAX_SLOT_TABLE);
>>>> -
>>>> - dprintk("--> %s: max_reqs=%u\n", __func__, max_slots);
>>>> -
>>>> - slot = kcalloc(max_slots, sizeof(struct nfs4_slot), GFP_NOFS);
>>>> - if (!slot)
>>>> + ret = nfs4_prealloc_slots(tbl, num_prealloc, ivalue);
>>>> + if (ret) {
>>>> + nfs4_free_all_slots(tbl);
>>>> goto out;
>>>> + }
>>>> ret = 0;
>>>>
>>>> spin_lock(&tbl->slot_tbl_lock);
>>>> tbl->max_slots = max_slots;
>>>> - tbl->slots = slot;
>>>> tbl->highest_used_slotid = -1; /* no slot is currently used */
>>>> spin_unlock(&tbl->slot_tbl_lock);
>>>> - dprintk("%s: tbl=%p slots=%p max_slots=%d\n", __func__,
>>>> - tbl, tbl->slots, tbl->max_slots);
>>>> + dprintk("%s: tbl=%p max_slots=%d, tbl->allocated_slots=%d\n", __func__,
>>>> + tbl, tbl->max_slots, tbl->allocated_slots);
>>>> out:
>>>> - dprintk("<-- %s: return %d\n", __func__, ret);
>>>> return ret;
>>>> }
>>>>
>>>> @@ -5063,30 +5213,34 @@ out:
>>>> static int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
>>>> {
>>>> struct nfs4_slot_table *tbl;
>>>> - int status;
>>>> + int status = 0;
>>>>
>>>> dprintk("--> %s\n", __func__);
>>>> /* Fore channel */
>>>> tbl = &ses->fc_slot_table;
>>>> - if (tbl->slots == NULL) {
>>>> - status = nfs4_init_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
>>>> + if (tbl->allocated_slots == 0) {
>>>> + status = nfs4_init_slot_table(tbl, ses->fc_attrs.max_reqs,
>>>> + ses->clp->cl_rpcclient->cl_xprt->min_reqs, 1);
>>>> if (status) /* -ENOMEM */
>>>> return status;
>>>> } else {
>>>> - status = nfs4_reset_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
>>>> - if (status)
>>>> - return status;
>>>> + nfs4_reset_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
>>>> }
>>>> +
>>>> /* Back channel */
>>>> tbl = &ses->bc_slot_table;
>>>> - if (tbl->slots == NULL) {
>>>> - status = nfs4_init_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
>>>> + if (tbl->allocated_slots == 0) {
>>>> + status = nfs4_init_slot_table(tbl, ses->bc_attrs.max_reqs,
>>>> + /* Backchannel max_reqs == 1 */
>>>> + ses->bc_attrs.max_reqs, 0);
>>>> if (status)
>>>> /* Fore and back channel share a connection so get
>>>> * both slot tables or neither */
>>>> nfs4_destroy_slot_tables(ses);
>>>> - } else
>>>> - status = nfs4_reset_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
>>>> + } else {
>>>> + nfs4_reset_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
>>>> + }
>>>> +
>>>> return status;
>>>> }
>>>>
>>>> @@ -5276,7 +5430,6 @@ int nfs4_proc_create_session(struct nfs_client *clp)
>>>>
>>>> /* Init or reset the session slot tables */
>>>> status = nfs4_setup_session_slot_tables(session);
>>>> - dprintk("slot table setup returned %d\n", status);
>>>> if (status)
>>>> goto out;
>>>>
>>>> @@ -5284,7 +5437,7 @@ int nfs4_proc_create_session(struct nfs_client *clp)
>>>> dprintk("%s client>seqid %d sessionid %u:%u:%u:%u\n", __func__,
>>>> clp->cl_seqid, ptr[0], ptr[1], ptr[2], ptr[3]);
>>>> out:
>>>> - dprintk("<-- %s\n", __func__);
>>>> + dprintk("<-- %s status %d\n", __func__, status);
>>>> return status;
>>>> }
>>>>
>>>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>>>> index 39914be..8260865 100644
>>>> --- a/fs/nfs/nfs4state.c
>>>> +++ b/fs/nfs/nfs4state.c
>>>> @@ -1573,26 +1573,16 @@ static int nfs4_recall_slot(struct nfs_client *clp)
>>>> {
>>>> struct nfs4_slot_table *fc_tbl = &clp->cl_session->fc_slot_table;
>>>> struct nfs4_channel_attrs *fc_attrs = &clp->cl_session->fc_attrs;
>>>> - struct nfs4_slot *new, *old;
>>>> - int i;
>>>>
>>>> nfs4_begin_drain_session(clp);
>>>> - new = kmalloc(fc_tbl->target_max_slots * sizeof(struct nfs4_slot),
>>>> - GFP_NOFS);
>>>> - if (!new)
>>>> - return -ENOMEM;
>>>>
>>>> spin_lock(&fc_tbl->slot_tbl_lock);
>>>> - for (i = 0; i < fc_tbl->target_max_slots; i++)
>>>> - new[i].seq_nr = fc_tbl->slots[i].seq_nr;
>>>> - old = fc_tbl->slots;
>>>> - fc_tbl->slots = new;
>>>> fc_tbl->max_slots = fc_tbl->target_max_slots;
>>>> + nfs4_reduce_slots_locked(fc_tbl);
>>>> fc_tbl->target_max_slots = 0;
>>>> fc_attrs->max_reqs = fc_tbl->max_slots;
>>>> spin_unlock(&fc_tbl->slot_tbl_lock);
>>>>
>>>> - kfree(old);
>>>> nfs4_end_drain_session(clp);
>>>> return 0;
>>>> }
>>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>>> index e6161b2..c42ec29 100644
>>>> --- a/fs/nfs/nfs4xdr.c
>>>> +++ b/fs/nfs/nfs4xdr.c
>>>> @@ -1872,7 +1872,6 @@ static void encode_sequence(struct xdr_stream *xdr,
>>>> #if defined(CONFIG_NFS_V4_1)
>>>> struct nfs4_session *session = args->sa_session;
>>>> struct nfs4_slot_table *tp;
>>>> - struct nfs4_slot *slot;
>>>> __be32 *p;
>>>>
>>>> if (!session)
>>>> @@ -1880,8 +1879,7 @@ static void encode_sequence(struct xdr_stream *xdr,
>>>>
>>>> tp = &session->fc_slot_table;
>>>>
>>>> - WARN_ON(args->sa_slotid == NFS4_MAX_SLOT_TABLE);
>>>> - slot = tp->slots + args->sa_slotid;
>>>> + WARN_ON(args->sa_slot->slotid == NFS4_MAX_SLOT_TABLE);
>>>>
>>>> p = reserve_space(xdr, 4 + NFS4_MAX_SESSIONID_LEN + 16);
>>>> *p++ = cpu_to_be32(OP_SEQUENCE);
>>>> @@ -1896,11 +1894,11 @@ static void encode_sequence(struct xdr_stream *xdr,
>>>> ((u32 *)session->sess_id.data)[1],
>>>> ((u32 *)session->sess_id.data)[2],
>>>> ((u32 *)session->sess_id.data)[3],
>>>> - slot->seq_nr, args->sa_slotid,
>>>> + args->sa_slot->seq_nr, args->sa_slot->slotid,
>>>> tp->highest_used_slotid, args->sa_cache_this);
>>>> p = xdr_encode_opaque_fixed(p, session->sess_id.data, NFS4_MAX_SESSIONID_LEN);
>>>> - *p++ = cpu_to_be32(slot->seq_nr);
>>>> - *p++ = cpu_to_be32(args->sa_slotid);
>>>> + *p++ = cpu_to_be32(args->sa_slot->seq_nr);
>>>> + *p++ = cpu_to_be32(args->sa_slot->slotid);
>>>> *p++ = cpu_to_be32(tp->highest_used_slotid);
>>>> *p = cpu_to_be32(args->sa_cache_this);
>>>> hdr->nops++;
>>>> @@ -5361,13 +5359,17 @@ static int decode_sequence(struct xdr_stream *xdr,
>>>> /* seqid */
>>>> dummy = be32_to_cpup(p++);
>>>> if (dummy != res->sr_slot->seq_nr) {
>>>> - dprintk("%s Invalid sequence number\n", __func__);
>>>> + dprintk("%s Invalid seq num %d for [slotid:seq_nr] [%d:%d]\n",
>>>> + __func__, dummy, res->sr_slot->slotid,
>>>> + res->sr_slot->seq_nr);
>>>> goto out_err;
>>>> }
>>>> /* slot id */
>>>> dummy = be32_to_cpup(p++);
>>>> - if (dummy != res->sr_slot - res->sr_session->fc_slot_table.slots) {
>>>> - dprintk("%s Invalid slot id\n", __func__);
>>>> + if (dummy != res->sr_slot->slotid) {
>>>> + dprintk("%s Invalid slot id %d for [slotid:seq_nr] [%d:%d]\n",
>>>> + __func__, dummy, res->sr_slot->slotid,
>>>> + res->sr_slot->seq_nr);
>>>> goto out_err;
>>>> }
>>>> /* highest slot id - currently not processed */
>>>> diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
>>>> index b5479df..90c6e2b 100644
>>>> --- a/include/linux/nfs_fs_sb.h
>>>> +++ b/include/linux/nfs_fs_sb.h
>>>> @@ -193,12 +193,15 @@ struct nfs_server {
>>>>
>>>> /* Sessions */
>>>> #define SLOT_TABLE_SZ (NFS4_MAX_SLOT_TABLE/(8*sizeof(long)))
>>>> +#define SLOT_TABLE_BITS 5
>>>> +#define SLOT_TABLE_SIZE (1 << SLOT_TABLE_BITS)
>>>> struct nfs4_slot_table {
>>>> - struct nfs4_slot *slots; /* seqid per slot */
>>>> + struct hlist_head slots[SLOT_TABLE_SIZE];
>>>> unsigned long used_slots[SLOT_TABLE_SZ]; /* used/unused bitmap */
>>>> spinlock_t slot_tbl_lock;
>>>> struct rpc_wait_queue slot_tbl_waitq; /* allocators may wait here */
>>>> - int max_slots; /* # slots in table */
>>>> + int allocated_slots; /* # slots in table */
>>>> + int max_slots; /* max # slots in table */
>>>> int highest_used_slotid; /* sent to server on each SEQ.
>>>> * op for dynamic resizing */
>>>> int target_max_slots; /* Set by CB_RECALL_SLOT as
>>>> @@ -206,11 +209,6 @@ struct nfs4_slot_table {
>>>> struct completion complete;
>>>> };
>>>>
>>>> -static inline int slot_idx(struct nfs4_slot_table *tbl, struct nfs4_slot *sp)
>>>> -{
>>>> - return sp - tbl->slots;
>>>> -}
>>>> -
>>>> /*
>>>> * Session related parameters
>>>> */
>>>> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
>>>> index c74595b..76b27a4 100644
>>>> --- a/include/linux/nfs_xdr.h
>>>> +++ b/include/linux/nfs_xdr.h
>>>> @@ -168,12 +168,14 @@ struct nfs4_channel_attrs {
>>>>
>>>> /* nfs41 sessions slot seqid */
>>>> struct nfs4_slot {
>>>> + struct hlist_node slot_node;
>>>> u32 seq_nr;
>>>> + u8 slotid;
>>>> };
>>>>
>>>> struct nfs4_sequence_args {
>>>> struct nfs4_session *sa_session;
>>>> - u8 sa_slotid;
>>>> + struct nfs4_slot *sa_slot;
>>>> u8 sa_cache_this;
>>>> };
>>>>
>>
>> --
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