This patch provides courteous server support for delegation only.
Only expired client with delegation but no conflict and no open
or lock state is allowed to be in COURTESY state.
Delegation conflict with COURTESY client is resolved by setting it
to EXPIRABLE, queue work for the laundromat and return delay to
caller. Conflict is resolved when the laudromat runs and expires
the EXIRABLE client while the NFS client retries the OPEN request.
Local thread request that gets conflict is doing the retry in
__break_lease.
Client in COURTESY state is allowed to reconnect and continues to
have access to its state while client in EXPIRABLE state is not.
To prevent 2 clients with the same name are on the conf_name_tree,
nfsd4_setclientid is modified to expire confirmed client in EXPIRABLE
state.
The spinlock cl_cs_lock is used to handle race conditions between
conflict resolver, nfsd_break_deleg_cb, and the COURTESY client
doing reconnect.
find_in_sessionid_hashtbl, find_confirmed_client_by_name and
find_confirmed_client are modified to activate COURTESY client by
setting it to ACTIVE state and skip client in EXPIRABLE state.
Signed-off-by: Dai Ngo <[email protected]>
---
fs/nfsd/nfs4state.c | 129 +++++++++++++++++++++++++++++++++++++++++++++-------
fs/nfsd/nfsd.h | 1 +
fs/nfsd/state.h | 63 +++++++++++++++++++++++++
3 files changed, 177 insertions(+), 16 deletions(-)
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 234e852fcdfa..fea5e24e7d94 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
+static struct workqueue_struct *laundry_wq;
+
static bool is_session_dead(struct nfsd4_session *ses)
{
return ses->se_flags & NFS4_SESSION_DEAD;
@@ -690,6 +692,14 @@ static unsigned int file_hashval(struct svc_fh *fh)
static struct hlist_head file_hashtbl[FILE_HASH_SIZE];
+static inline void
+run_laundromat(struct nfsd_net *nn, bool wait)
+{
+ mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
+ if (wait)
+ flush_workqueue(laundry_wq);
+}
+
static void
__nfs4_file_get_access(struct nfs4_file *fp, u32 access)
{
@@ -1939,6 +1949,11 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
session = __find_in_sessionid_hashtbl(sessionid, net);
if (!session)
goto out;
+ if (!try_to_activate_client(session->se_client)) {
+ /* client is EXPIRABLE */
+ session = NULL;
+ goto out;
+ }
status = nfsd4_get_session_locked(session);
if (status)
session = NULL;
@@ -2004,6 +2019,7 @@ static struct nfs4_client *alloc_client(struct xdr_netobj name)
idr_init(&clp->cl_stateids);
atomic_set(&clp->cl_rpc_users, 0);
clp->cl_cb_state = NFSD4_CB_UNKNOWN;
+ clp->cl_state = NFSD4_ACTIVE;
INIT_LIST_HEAD(&clp->cl_idhash);
INIT_LIST_HEAD(&clp->cl_openowners);
INIT_LIST_HEAD(&clp->cl_delegations);
@@ -2015,6 +2031,7 @@ static struct nfs4_client *alloc_client(struct xdr_netobj name)
INIT_LIST_HEAD(&clp->async_copies);
spin_lock_init(&clp->async_lock);
spin_lock_init(&clp->cl_lock);
+ spin_lock_init(&clp->cl_cs_lock);
rpc_init_wait_queue(&clp->cl_cb_waitq, "Backchannel slot table");
return clp;
err_no_hashtbl:
@@ -2890,9 +2907,13 @@ static struct nfs4_client *
find_confirmed_client(clientid_t *clid, bool sessions, struct nfsd_net *nn)
{
struct list_head *tbl = nn->conf_id_hashtbl;
+ struct nfs4_client *clp;
lockdep_assert_held(&nn->client_lock);
- return find_client_in_id_table(tbl, clid, sessions);
+ clp = find_client_in_id_table(tbl, clid, sessions);
+ if (clp && !try_to_activate_client(clp))
+ clp = NULL;
+ return clp;
}
static struct nfs4_client *
@@ -2912,8 +2933,13 @@ static bool clp_used_exchangeid(struct nfs4_client *clp)
static struct nfs4_client *
find_confirmed_client_by_name(struct xdr_netobj *name, struct nfsd_net *nn)
{
+ struct nfs4_client *clp;
+
lockdep_assert_held(&nn->client_lock);
- return find_clp_in_name_tree(name, &nn->conf_name_tree);
+ clp = find_clp_in_name_tree(name, &nn->conf_name_tree);
+ if (clp && !try_to_activate_client(clp))
+ clp = NULL;
+ return clp;
}
static struct nfs4_client *
@@ -4030,12 +4056,25 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
struct nfs4_client *unconf = NULL;
__be32 status;
struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+ struct nfs4_client *expired = NULL;
new = create_client(clname, rqstp, &clverifier);
if (new == NULL)
return nfserr_jukebox;
spin_lock(&nn->client_lock);
- conf = find_confirmed_client_by_name(&clname, nn);
+ conf = find_clp_in_name_tree(&clname, &nn->conf_name_tree);
+ if (conf) {
+ if (!try_to_activate_client(conf)) {
+ /*
+ * remove EXPIRABLE client from conf_name_tree so
+ * when the new client is confirmed there won't be
+ * 2 clients with the same name on the conf_name_tree.
+ */
+ if (!mark_client_expired_locked(conf))
+ expired = conf;
+ conf = NULL;
+ }
+ }
if (conf && client_has_state(conf)) {
status = nfserr_clid_inuse;
if (clp_used_exchangeid(conf))
@@ -4073,6 +4112,8 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
trace_nfsd_clid_expire_unconf(&unconf->cl_clientid);
expire_client(unconf);
}
+ if (expired)
+ expire_client(expired);
return status;
}
@@ -4694,9 +4735,16 @@ nfsd_break_deleg_cb(struct file_lock *fl)
bool ret = false;
struct nfs4_delegation *dp = (struct nfs4_delegation *)fl->fl_owner;
struct nfs4_file *fp = dp->dl_stid.sc_file;
+ struct nfs4_client *clp = dp->dl_stid.sc_client;
+ struct nfsd_net *nn;
trace_nfsd_cb_recall(&dp->dl_stid);
+ if (try_to_expire_client(clp)) {
+ nn = net_generic(clp->net, nfsd_net_id);
+ run_laundromat(nn, false);
+ }
+
/*
* We don't want the locks code to timeout the lease for us;
* we'll remove it ourself if a delegation isn't returned
@@ -5605,6 +5653,64 @@ static void nfsd4_ssc_expire_umount(struct nfsd_net *nn)
}
#endif
+/*
+ * place holder for now, no check for lock blockers yet
+ */
+static bool
+nfs4_anylock_blockers(struct nfs4_client *clp)
+{
+ /*
+ * don't want to check for delegation conflict here since
+ * we need the state_lock for it. The laundromat willexpire
+ * COURTESY later when checking for delegation recall timeout.
+ */
+ return false;
+}
+
+static bool client_has_state_tmp(struct nfs4_client *clp)
+{
+ if (!list_empty(&clp->cl_delegations) &&
+ !client_has_openowners(clp) &&
+ list_empty(&clp->async_copies))
+ return true;
+ return false;
+}
+
+static void
+nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
+ struct laundry_time *lt)
+{
+ struct list_head *pos, *next;
+ struct nfs4_client *clp;
+ bool cour;
+
+ INIT_LIST_HEAD(reaplist);
+ spin_lock(&nn->client_lock);
+ list_for_each_safe(pos, next, &nn->client_lru) {
+ clp = list_entry(pos, struct nfs4_client, cl_lru);
+ if (clp->cl_state == NFSD4_EXPIRABLE)
+ goto exp_client;
+ if (!state_expired(lt, clp->cl_time))
+ break;
+ if (!client_has_state_tmp(clp))
+ goto exp_client;
+ cour = (clp->cl_state == NFSD4_COURTESY);
+ if (cour && ktime_get_boottime_seconds() >=
+ (clp->cl_time + NFSD_COURTESY_CLIENT_TIMEOUT))
+ goto exp_client;
+ if (nfs4_anylock_blockers(clp)) {
+exp_client:
+ if (mark_client_expired_locked(clp))
+ continue;
+ list_add(&clp->cl_lru, reaplist);
+ continue;
+ }
+ if (!cour)
+ cmpxchg(&clp->cl_state, NFSD4_ACTIVE, NFSD4_COURTESY);
+ }
+ spin_unlock(&nn->client_lock);
+}
+
static time64_t
nfs4_laundromat(struct nfsd_net *nn)
{
@@ -5627,7 +5733,6 @@ nfs4_laundromat(struct nfsd_net *nn)
goto out;
}
nfsd4_end_grace(nn);
- INIT_LIST_HEAD(&reaplist);
spin_lock(&nn->s2s_cp_lock);
idr_for_each_entry(&nn->s2s_cp_stateids, cps_t, i) {
@@ -5637,17 +5742,7 @@ nfs4_laundromat(struct nfsd_net *nn)
_free_cpntf_state_locked(nn, cps);
}
spin_unlock(&nn->s2s_cp_lock);
-
- spin_lock(&nn->client_lock);
- list_for_each_safe(pos, next, &nn->client_lru) {
- clp = list_entry(pos, struct nfs4_client, cl_lru);
- if (!state_expired(<, clp->cl_time))
- break;
- if (mark_client_expired_locked(clp))
- continue;
- list_add(&clp->cl_lru, &reaplist);
- }
- spin_unlock(&nn->client_lock);
+ nfs4_get_client_reaplist(nn, &reaplist, <);
list_for_each_safe(pos, next, &reaplist) {
clp = list_entry(pos, struct nfs4_client, cl_lru);
trace_nfsd_clid_purged(&clp->cl_clientid);
@@ -5657,6 +5752,9 @@ nfs4_laundromat(struct nfsd_net *nn)
spin_lock(&state_lock);
list_for_each_safe(pos, next, &nn->del_recall_lru) {
dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
+
+ clp = dp->dl_stid.sc_client;
+ try_to_expire_client(dp->dl_stid.sc_client);
if (!state_expired(<, dp->dl_time))
break;
WARN_ON(!unhash_delegation_locked(dp));
@@ -5722,7 +5820,6 @@ nfs4_laundromat(struct nfsd_net *nn)
return max_t(time64_t, lt.new_timeo, NFSD_LAUNDROMAT_MINTIMEOUT);
}
-static struct workqueue_struct *laundry_wq;
static void laundromat_main(struct work_struct *);
static void
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 4fc1fd639527..23996c6ca75e 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -336,6 +336,7 @@ void nfsd_lockd_shutdown(void);
#define COMPOUND_ERR_SLACK_SPACE 16 /* OP_SETATTR */
#define NFSD_LAUNDROMAT_MINTIMEOUT 1 /* seconds */
+#define NFSD_COURTESY_CLIENT_TIMEOUT (24 * 60 * 60) /* seconds */
/*
* The following attributes are currently not supported by the NFSv4 server:
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 95457cfd37fc..b7d243073c58 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -283,6 +283,28 @@ struct nfsd4_sessionid {
#define HEXDIR_LEN 33 /* hex version of 16 byte md5 of cl_name plus '\0' */
/*
+ * State Meaning Where set
+ * --------------------------------------------------------------------------
+ * | NFSD4_ACTIVE | Confirmed, active | Default |
+ * |------------------- ----------------------------------------------------|
+ * | NFSD4_COURTESY | Courtesy state. | nfs4_get_client_reaplist |
+ * | | Lease/lock/share | |
+ * | | reservation conflict | |
+ * | | can cause Courtesy | |
+ * | | client to be expired | |
+ * |------------------------------------------------------------------------|
+ * | NFSD4_EXPIRABLE | Courtesy client to be| nfs4_laundromat |
+ * | | expired by Laundromat| try_to_expire_client |
+ * | | due to conflict | |
+ * |------------------------------------------------------------------------|
+ */
+enum {
+ NFSD4_ACTIVE = 0,
+ NFSD4_COURTESY,
+ NFSD4_EXPIRABLE,
+};
+
+/*
* struct nfs4_client - one per client. Clientids live here.
*
* The initial object created by an NFS client using SETCLIENTID (for NFSv4.0)
@@ -385,6 +407,9 @@ struct nfs4_client {
struct list_head async_copies; /* list of async copies */
spinlock_t async_lock; /* lock for async copies */
atomic_t cl_cb_inflight; /* Outstanding callbacks */
+
+ spinlock_t cl_cs_lock;
+ unsigned int cl_state;
};
/* struct nfs4_client_reset
@@ -702,4 +727,42 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
extern int nfsd4_client_record_check(struct nfs4_client *clp);
extern void nfsd4_record_grace_done(struct nfsd_net *nn);
+static inline bool try_to_expire_client(struct nfs4_client *clp)
+{
+ bool ret;
+
+ spin_lock(&clp->cl_cs_lock);
+ if (clp->cl_state == NFSD4_EXPIRABLE) {
+ spin_unlock(&clp->cl_cs_lock);
+ return true;
+ }
+ ret = NFSD4_COURTESY ==
+ cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
+ spin_unlock(&clp->cl_cs_lock);
+ return ret;
+}
+
+static inline bool try_to_activate_client(struct nfs4_client *clp)
+{
+ bool ret;
+ struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
+
+ /* sync with laundromat */
+ lockdep_assert_held(&nn->client_lock);
+
+ /* sync with try_to_expire_client */
+ spin_lock(&clp->cl_cs_lock);
+ if (clp->cl_state == NFSD4_ACTIVE) {
+ spin_unlock(&clp->cl_cs_lock);
+ return true;
+ }
+ if (clp->cl_state == NFSD4_EXPIRABLE) {
+ spin_unlock(&clp->cl_cs_lock);
+ return false;
+ }
+ ret = NFSD4_COURTESY ==
+ cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_ACTIVE);
+ spin_unlock(&clp->cl_cs_lock);
+ return ret;
+}
#endif /* NFSD4_STATE_H */
--
2.9.5
On 4/25/22 1:40 PM, J. Bruce Fields wrote:
> On Mon, Apr 25, 2022 at 12:42:58PM -0700, [email protected] wrote:
>> On 4/25/22 11:51 AM, J. Bruce Fields wrote:
>>> On Sat, Apr 23, 2022 at 11:44:09AM -0700, Dai Ngo wrote:
>>>> This patch provides courteous server support for delegation only.
>>>> Only expired client with delegation but no conflict and no open
>>>> or lock state is allowed to be in COURTESY state.
>>>>
>>>> Delegation conflict with COURTESY client is resolved by setting it
>>>> to EXPIRABLE, queue work for the laundromat and return delay to
>>>> caller. Conflict is resolved when the laudromat runs and expires
>>>> the EXIRABLE client while the NFS client retries the OPEN request.
>>>> Local thread request that gets conflict is doing the retry in
>>>> __break_lease.
>>>>
>>>> Client in COURTESY state is allowed to reconnect and continues to
>>>> have access to its state while client in EXPIRABLE state is not.
>>>> To prevent 2 clients with the same name are on the conf_name_tree,
>>>> nfsd4_setclientid is modified to expire confirmed client in EXPIRABLE
>>>> state.
>>>>
>>>> The spinlock cl_cs_lock is used to handle race conditions between
>>>> conflict resolver, nfsd_break_deleg_cb, and the COURTESY client
>>>> doing reconnect.
>>>>
>>>> find_in_sessionid_hashtbl, find_confirmed_client_by_name and
>>>> find_confirmed_client are modified to activate COURTESY client by
>>>> setting it to ACTIVE state and skip client in EXPIRABLE state.
>>>>
>>>> Signed-off-by: Dai Ngo <[email protected]>
>>>> ---
>>>> fs/nfsd/nfs4state.c | 129 +++++++++++++++++++++++++++++++++++++++++++++-------
>>>> fs/nfsd/nfsd.h | 1 +
>>>> fs/nfsd/state.h | 63 +++++++++++++++++++++++++
>>>> 3 files changed, 177 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>>> index 234e852fcdfa..fea5e24e7d94 100644
>>>> --- a/fs/nfsd/nfs4state.c
>>>> +++ b/fs/nfsd/nfs4state.c
>>>> @@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
>>>> static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
>>>> static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
>>>> +static struct workqueue_struct *laundry_wq;
>>>> +
>>>> static bool is_session_dead(struct nfsd4_session *ses)
>>>> {
>>>> return ses->se_flags & NFS4_SESSION_DEAD;
>>>> @@ -690,6 +692,14 @@ static unsigned int file_hashval(struct svc_fh *fh)
>>>> static struct hlist_head file_hashtbl[FILE_HASH_SIZE];
>>>> +static inline void
>>>> +run_laundromat(struct nfsd_net *nn, bool wait)
>>>> +{
>>>> + mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
>>>> + if (wait)
>>>> + flush_workqueue(laundry_wq);
>>>> +}
>>> Let's keep those two things separate. The "wait" argument isn't
>>> self-documenting when reading the calling code.
>> we can use enum to spell out the intention.
>>
>>> And the
>>> mod_delayed_work call isn't always needed before flush_workqueue.
>> ok. I'll keep them separate.
>>
>>>> +
>>>> static void
>>>> __nfs4_file_get_access(struct nfs4_file *fp, u32 access)
>>>> {
>>>> @@ -1939,6 +1949,11 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
>>>> session = __find_in_sessionid_hashtbl(sessionid, net);
>>>> if (!session)
>>>> goto out;
>>>> + if (!try_to_activate_client(session->se_client)) {
>>>> + /* client is EXPIRABLE */
>>>> + session = NULL;
>>>> + goto out;
>>> No, we definitely don't want to do this. As I said before, an
>>> "expirable client" should be treated in every way exactly like any
>>> regular active client. Literally the only difference is that the
>>> laundromat can try to expire it.
>> Do you mean leave the state as EXPIRABLE but allow the callers
>> to use the client as an ACTIVE client:
> The only place we should even be checking whether a client is EXPIRABLE
> is in the laundromat thread, in the loop over the client_lru. Even
> there, EXPIRABLE being set doesn't mean the client *has* to be expired,
> the real decision is left to mark_client_expired_locked(), as it
> currently is.
>
>> static inline bool try_to_expire_client(struct nfs4_client *clp)
>> {
>> bool ret;
>>
>> spin_lock(&clp->cl_cs_lock);
>> if (clp->cl_state == NFSD4_EXPIRABLE) {
>> spin_unlock(&clp->cl_cs_lock);
>> return false; <<<====== was true
>> }
>> ret = NFSD4_COURTESY ==
>> cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
>> spin_unlock(&clp->cl_cs_lock);
>> return ret;
>> }
> So, try_to_expire_client(), as I said, should be just
>
> static bool try_to_expire_client(struct nfs4_client *clp)
> {
> return COURTESY == cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
> }
>
> Except, OK, I did forget that somebody else could have already set
> EXPIRABLE, and we still want to tell the caller to retry in that case,
> so, oops, let's make it:
>
> return ACTIVE != cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
So functionally this is the same as what i have in the patch, except this
makes it simpler?
Do we need to make any change in try_to_activate_client to work with
this change in try_to_expire_client?
>
> In other words: set EXPIRABLE if and only if the state is COURTESY, and
> then tell the caller to retry the operation if and only if the state was
> previously COURTESY or EXPIRABLE.
>
> But we shouldn't need the cl_cs_lock,
The cl_cs_lock is to synchronize between COURTESY client trying to
reconnect (try_to_activate_client) and another thread is trying to
resolve a delegation/share/lock conflict (try_to_expire_client).
So you don't think this is necessary?
-Dai
> and certainly shouldn't be failing
> lookups of EXPIRABLE clients.
>
>
>
> --b.
>
>
>> -Dai
>>
>>> And then all this code becomes unnecessary:
>>>
>>>> @@ -702,4 +727,42 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
>>>> extern int nfsd4_client_record_check(struct nfs4_client *clp);
>>>> extern void nfsd4_record_grace_done(struct nfsd_net *nn);
>>>> +static inline bool try_to_expire_client(struct nfs4_client *clp)
>>>> +{
>>>> + bool ret;
>>>> +
>>>> + spin_lock(&clp->cl_cs_lock);
>>>> + if (clp->cl_state == NFSD4_EXPIRABLE) {
>>>> + spin_unlock(&clp->cl_cs_lock);
>>>> + return true;
>>>> + }
>>>> + ret = NFSD4_COURTESY ==
>>>> + cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
>>>> + spin_unlock(&clp->cl_cs_lock);
>>>> + return ret;
>>>> +}
>>>> +
>>>> +static inline bool try_to_activate_client(struct nfs4_client *clp)
>>>> +{
>>>> + bool ret;
>>>> + struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
>>>> +
>>>> + /* sync with laundromat */
>>>> + lockdep_assert_held(&nn->client_lock);
>>>> +
>>>> + /* sync with try_to_expire_client */
>>>> + spin_lock(&clp->cl_cs_lock);
>>>> + if (clp->cl_state == NFSD4_ACTIVE) {
>>>> + spin_unlock(&clp->cl_cs_lock);
>>>> + return true;
>>>> + }
>>>> + if (clp->cl_state == NFSD4_EXPIRABLE) {
>>>> + spin_unlock(&clp->cl_cs_lock);
>>>> + return false;
>>>> + }
>>>> + ret = NFSD4_COURTESY ==
>>>> + cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_ACTIVE);
>>>> + spin_unlock(&clp->cl_cs_lock);
>>>> + return ret;
>>>> +}
>>> --b.
On 4/25/22 2:48 PM, J. Bruce Fields wrote:
> On Mon, Apr 25, 2022 at 02:35:27PM -0700, [email protected] wrote:
>> On 4/25/22 1:40 PM, J. Bruce Fields wrote:
>>> On Mon, Apr 25, 2022 at 12:42:58PM -0700, [email protected] wrote:
>>>> static inline bool try_to_expire_client(struct nfs4_client *clp)
>>>> {
>>>> bool ret;
>>>>
>>>> spin_lock(&clp->cl_cs_lock);
>>>> if (clp->cl_state == NFSD4_EXPIRABLE) {
>>>> spin_unlock(&clp->cl_cs_lock);
>>>> return false; <<<====== was true
>>>> }
>>>> ret = NFSD4_COURTESY ==
>>>> cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
>>>> spin_unlock(&clp->cl_cs_lock);
>>>> return ret;
>>>> }
>>> So, try_to_expire_client(), as I said, should be just
>>>
>>> static bool try_to_expire_client(struct nfs4_client *clp)
>>> {
>>> return COURTESY == cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
>>> }
>>>
>>> Except, OK, I did forget that somebody else could have already set
>>> EXPIRABLE, and we still want to tell the caller to retry in that case,
>>> so, oops, let's make it:
>>>
>>> return ACTIVE != cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
>> So functionally this is the same as what i have in the patch, except this
>> makes it simpler?
> Right.
>
> And my main complaint is still about the code that fails lookups of
> EXPIRABLE clients. We shouldn't need to modify find_in_sessionid_hastbl
> or other client lookups.
>
>> Do we need to make any change in try_to_activate_client to work with
>> this change in try_to_expire_client?
>>
>>> In other words: set EXPIRABLE if and only if the state is COURTESY, and
>>> then tell the caller to retry the operation if and only if the state was
>>> previously COURTESY or EXPIRABLE.
>>>
>>> But we shouldn't need the cl_cs_lock,
>> The cl_cs_lock is to synchronize between COURTESY client trying to
>> reconnect (try_to_activate_client) and another thread is trying to
>> resolve a delegation/share/lock conflict (try_to_expire_client).
>> So you don't think this is necessary?
> Correct, it's not necessary.
>
> The only synchronization is provided by mark_client_expired_locked and
> get_client_locked.
>
> We don't need try_to_activate_client. Just set cl_state to ACTIVE in
> get_client_locked.
ok, what you suggested seems to work. I will remove try_to_activate_client
and just set cl_state to ACTIVE and test it to see if there is any problems
that we haven't thought of with this scheme.
-Dai
>
> --b.
On 4/25/22 11:51 AM, J. Bruce Fields wrote:
> On Sat, Apr 23, 2022 at 11:44:09AM -0700, Dai Ngo wrote:
>> This patch provides courteous server support for delegation only.
>> Only expired client with delegation but no conflict and no open
>> or lock state is allowed to be in COURTESY state.
>>
>> Delegation conflict with COURTESY client is resolved by setting it
>> to EXPIRABLE, queue work for the laundromat and return delay to
>> caller. Conflict is resolved when the laudromat runs and expires
>> the EXIRABLE client while the NFS client retries the OPEN request.
>> Local thread request that gets conflict is doing the retry in
>> __break_lease.
>>
>> Client in COURTESY state is allowed to reconnect and continues to
>> have access to its state while client in EXPIRABLE state is not.
>> To prevent 2 clients with the same name are on the conf_name_tree,
>> nfsd4_setclientid is modified to expire confirmed client in EXPIRABLE
>> state.
>>
>> The spinlock cl_cs_lock is used to handle race conditions between
>> conflict resolver, nfsd_break_deleg_cb, and the COURTESY client
>> doing reconnect.
>>
>> find_in_sessionid_hashtbl, find_confirmed_client_by_name and
>> find_confirmed_client are modified to activate COURTESY client by
>> setting it to ACTIVE state and skip client in EXPIRABLE state.
>>
>> Signed-off-by: Dai Ngo <[email protected]>
>> ---
>> fs/nfsd/nfs4state.c | 129 +++++++++++++++++++++++++++++++++++++++++++++-------
>> fs/nfsd/nfsd.h | 1 +
>> fs/nfsd/state.h | 63 +++++++++++++++++++++++++
>> 3 files changed, 177 insertions(+), 16 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index 234e852fcdfa..fea5e24e7d94 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
>> static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
>> static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
>>
>> +static struct workqueue_struct *laundry_wq;
>> +
>> static bool is_session_dead(struct nfsd4_session *ses)
>> {
>> return ses->se_flags & NFS4_SESSION_DEAD;
>> @@ -690,6 +692,14 @@ static unsigned int file_hashval(struct svc_fh *fh)
>>
>> static struct hlist_head file_hashtbl[FILE_HASH_SIZE];
>>
>> +static inline void
>> +run_laundromat(struct nfsd_net *nn, bool wait)
>> +{
>> + mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
>> + if (wait)
>> + flush_workqueue(laundry_wq);
>> +}
> Let's keep those two things separate. The "wait" argument isn't
> self-documenting when reading the calling code.
we can use enum to spell out the intention.
> And the
> mod_delayed_work call isn't always needed before flush_workqueue.
ok. I'll keep them separate.
>
>> +
>> static void
>> __nfs4_file_get_access(struct nfs4_file *fp, u32 access)
>> {
>> @@ -1939,6 +1949,11 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
>> session = __find_in_sessionid_hashtbl(sessionid, net);
>> if (!session)
>> goto out;
>> + if (!try_to_activate_client(session->se_client)) {
>> + /* client is EXPIRABLE */
>> + session = NULL;
>> + goto out;
> No, we definitely don't want to do this. As I said before, an
> "expirable client" should be treated in every way exactly like any
> regular active client. Literally the only difference is that the
> laundromat can try to expire it.
Do you mean leave the state as EXPIRABLE but allow the callers
to use the client as an ACTIVE client:
static inline bool try_to_expire_client(struct nfs4_client *clp)
{
bool ret;
spin_lock(&clp->cl_cs_lock);
if (clp->cl_state == NFSD4_EXPIRABLE) {
spin_unlock(&clp->cl_cs_lock);
return false; <<<====== was true
}
ret = NFSD4_COURTESY ==
cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
spin_unlock(&clp->cl_cs_lock);
return ret;
}
-Dai
>
> And then all this code becomes unnecessary:
>
>> @@ -702,4 +727,42 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
>> extern int nfsd4_client_record_check(struct nfs4_client *clp);
>> extern void nfsd4_record_grace_done(struct nfsd_net *nn);
>>
>> +static inline bool try_to_expire_client(struct nfs4_client *clp)
>> +{
>> + bool ret;
>> +
>> + spin_lock(&clp->cl_cs_lock);
>> + if (clp->cl_state == NFSD4_EXPIRABLE) {
>> + spin_unlock(&clp->cl_cs_lock);
>> + return true;
>> + }
>> + ret = NFSD4_COURTESY ==
>> + cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
>> + spin_unlock(&clp->cl_cs_lock);
>> + return ret;
>> +}
>> +
>> +static inline bool try_to_activate_client(struct nfs4_client *clp)
>> +{
>> + bool ret;
>> + struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
>> +
>> + /* sync with laundromat */
>> + lockdep_assert_held(&nn->client_lock);
>> +
>> + /* sync with try_to_expire_client */
>> + spin_lock(&clp->cl_cs_lock);
>> + if (clp->cl_state == NFSD4_ACTIVE) {
>> + spin_unlock(&clp->cl_cs_lock);
>> + return true;
>> + }
>> + if (clp->cl_state == NFSD4_EXPIRABLE) {
>> + spin_unlock(&clp->cl_cs_lock);
>> + return false;
>> + }
>> + ret = NFSD4_COURTESY ==
>> + cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_ACTIVE);
>> + spin_unlock(&clp->cl_cs_lock);
>> + return ret;
>> +}
> --b.
On Mon, Apr 25, 2022 at 03:24:49PM -0700, [email protected] wrote:
>
> On 4/25/22 2:48 PM, J. Bruce Fields wrote:
> >On Mon, Apr 25, 2022 at 02:35:27PM -0700, [email protected] wrote:
> >>On 4/25/22 1:40 PM, J. Bruce Fields wrote:
> >>>On Mon, Apr 25, 2022 at 12:42:58PM -0700, [email protected] wrote:
> >>>>static inline bool try_to_expire_client(struct nfs4_client *clp)
> >>>>{
> >>>> bool ret;
> >>>>
> >>>> spin_lock(&clp->cl_cs_lock);
> >>>> if (clp->cl_state == NFSD4_EXPIRABLE) {
> >>>> spin_unlock(&clp->cl_cs_lock);
> >>>> return false; <<<====== was true
> >>>> }
> >>>> ret = NFSD4_COURTESY ==
> >>>> cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
> >>>> spin_unlock(&clp->cl_cs_lock);
> >>>> return ret;
> >>>>}
> >>>So, try_to_expire_client(), as I said, should be just
> >>>
> >>> static bool try_to_expire_client(struct nfs4_client *clp)
> >>> {
> >>> return COURTESY == cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
> >>> }
> >>>
> >>>Except, OK, I did forget that somebody else could have already set
> >>>EXPIRABLE, and we still want to tell the caller to retry in that case,
> >>>so, oops, let's make it:
> >>>
> >>> return ACTIVE != cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
> >>So functionally this is the same as what i have in the patch, except this
> >>makes it simpler?
> >Right.
> >
> >And my main complaint is still about the code that fails lookups of
> >EXPIRABLE clients. We shouldn't need to modify find_in_sessionid_hastbl
> >or other client lookups.
> >
> >>Do we need to make any change in try_to_activate_client to work with
> >>this change in try_to_expire_client?
> >>
> >>>In other words: set EXPIRABLE if and only if the state is COURTESY, and
> >>>then tell the caller to retry the operation if and only if the state was
> >>>previously COURTESY or EXPIRABLE.
> >>>
> >>>But we shouldn't need the cl_cs_lock,
> >>The cl_cs_lock is to synchronize between COURTESY client trying to
> >>reconnect (try_to_activate_client) and another thread is trying to
> >>resolve a delegation/share/lock conflict (try_to_expire_client).
> >>So you don't think this is necessary?
> >Correct, it's not necessary.
> >
> >The only synchronization is provided by mark_client_expired_locked and
> >get_client_locked.
> >
> >We don't need try_to_activate_client. Just set cl_state to ACTIVE in
> >get_client_locked.
>
> ok, what you suggested seems to work. I will remove try_to_activate_client
> and just set cl_state to ACTIVE and test it to see if there is any problems
> that we haven't thought of with this scheme.
Thanks!
--b.
On Mon, Apr 25, 2022 at 12:42:58PM -0700, [email protected] wrote:
>
> On 4/25/22 11:51 AM, J. Bruce Fields wrote:
> >On Sat, Apr 23, 2022 at 11:44:09AM -0700, Dai Ngo wrote:
> >>This patch provides courteous server support for delegation only.
> >>Only expired client with delegation but no conflict and no open
> >>or lock state is allowed to be in COURTESY state.
> >>
> >>Delegation conflict with COURTESY client is resolved by setting it
> >>to EXPIRABLE, queue work for the laundromat and return delay to
> >>caller. Conflict is resolved when the laudromat runs and expires
> >>the EXIRABLE client while the NFS client retries the OPEN request.
> >>Local thread request that gets conflict is doing the retry in
> >>__break_lease.
> >>
> >>Client in COURTESY state is allowed to reconnect and continues to
> >>have access to its state while client in EXPIRABLE state is not.
> >>To prevent 2 clients with the same name are on the conf_name_tree,
> >>nfsd4_setclientid is modified to expire confirmed client in EXPIRABLE
> >>state.
> >>
> >>The spinlock cl_cs_lock is used to handle race conditions between
> >>conflict resolver, nfsd_break_deleg_cb, and the COURTESY client
> >>doing reconnect.
> >>
> >>find_in_sessionid_hashtbl, find_confirmed_client_by_name and
> >>find_confirmed_client are modified to activate COURTESY client by
> >>setting it to ACTIVE state and skip client in EXPIRABLE state.
> >>
> >>Signed-off-by: Dai Ngo <[email protected]>
> >>---
> >> fs/nfsd/nfs4state.c | 129 +++++++++++++++++++++++++++++++++++++++++++++-------
> >> fs/nfsd/nfsd.h | 1 +
> >> fs/nfsd/state.h | 63 +++++++++++++++++++++++++
> >> 3 files changed, 177 insertions(+), 16 deletions(-)
> >>
> >>diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> >>index 234e852fcdfa..fea5e24e7d94 100644
> >>--- a/fs/nfsd/nfs4state.c
> >>+++ b/fs/nfsd/nfs4state.c
> >>@@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
> >> static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
> >> static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
> >>+static struct workqueue_struct *laundry_wq;
> >>+
> >> static bool is_session_dead(struct nfsd4_session *ses)
> >> {
> >> return ses->se_flags & NFS4_SESSION_DEAD;
> >>@@ -690,6 +692,14 @@ static unsigned int file_hashval(struct svc_fh *fh)
> >> static struct hlist_head file_hashtbl[FILE_HASH_SIZE];
> >>+static inline void
> >>+run_laundromat(struct nfsd_net *nn, bool wait)
> >>+{
> >>+ mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
> >>+ if (wait)
> >>+ flush_workqueue(laundry_wq);
> >>+}
> >Let's keep those two things separate. The "wait" argument isn't
> >self-documenting when reading the calling code.
>
> we can use enum to spell out the intention.
>
> > And the
> >mod_delayed_work call isn't always needed before flush_workqueue.
>
> ok. I'll keep them separate.
>
> >
> >>+
> >> static void
> >> __nfs4_file_get_access(struct nfs4_file *fp, u32 access)
> >> {
> >>@@ -1939,6 +1949,11 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
> >> session = __find_in_sessionid_hashtbl(sessionid, net);
> >> if (!session)
> >> goto out;
> >>+ if (!try_to_activate_client(session->se_client)) {
> >>+ /* client is EXPIRABLE */
> >>+ session = NULL;
> >>+ goto out;
> >No, we definitely don't want to do this. As I said before, an
> >"expirable client" should be treated in every way exactly like any
> >regular active client. Literally the only difference is that the
> >laundromat can try to expire it.
>
> Do you mean leave the state as EXPIRABLE but allow the callers
> to use the client as an ACTIVE client:
The only place we should even be checking whether a client is EXPIRABLE
is in the laundromat thread, in the loop over the client_lru. Even
there, EXPIRABLE being set doesn't mean the client *has* to be expired,
the real decision is left to mark_client_expired_locked(), as it
currently is.
> static inline bool try_to_expire_client(struct nfs4_client *clp)
> {
> bool ret;
>
> spin_lock(&clp->cl_cs_lock);
> if (clp->cl_state == NFSD4_EXPIRABLE) {
> spin_unlock(&clp->cl_cs_lock);
> return false; <<<====== was true
> }
> ret = NFSD4_COURTESY ==
> cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
> spin_unlock(&clp->cl_cs_lock);
> return ret;
> }
So, try_to_expire_client(), as I said, should be just
static bool try_to_expire_client(struct nfs4_client *clp)
{
return COURTESY == cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
}
Except, OK, I did forget that somebody else could have already set
EXPIRABLE, and we still want to tell the caller to retry in that case,
so, oops, let's make it:
return ACTIVE != cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
In other words: set EXPIRABLE if and only if the state is COURTESY, and
then tell the caller to retry the operation if and only if the state was
previously COURTESY or EXPIRABLE.
But we shouldn't need the cl_cs_lock, and certainly shouldn't be failing
lookups of EXPIRABLE clients.
--b.
>
> -Dai
>
> >
> >And then all this code becomes unnecessary:
> >
> >>@@ -702,4 +727,42 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
> >> extern int nfsd4_client_record_check(struct nfs4_client *clp);
> >> extern void nfsd4_record_grace_done(struct nfsd_net *nn);
> >>+static inline bool try_to_expire_client(struct nfs4_client *clp)
> >>+{
> >>+ bool ret;
> >>+
> >>+ spin_lock(&clp->cl_cs_lock);
> >>+ if (clp->cl_state == NFSD4_EXPIRABLE) {
> >>+ spin_unlock(&clp->cl_cs_lock);
> >>+ return true;
> >>+ }
> >>+ ret = NFSD4_COURTESY ==
> >>+ cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
> >>+ spin_unlock(&clp->cl_cs_lock);
> >>+ return ret;
> >>+}
> >>+
> >>+static inline bool try_to_activate_client(struct nfs4_client *clp)
> >>+{
> >>+ bool ret;
> >>+ struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
> >>+
> >>+ /* sync with laundromat */
> >>+ lockdep_assert_held(&nn->client_lock);
> >>+
> >>+ /* sync with try_to_expire_client */
> >>+ spin_lock(&clp->cl_cs_lock);
> >>+ if (clp->cl_state == NFSD4_ACTIVE) {
> >>+ spin_unlock(&clp->cl_cs_lock);
> >>+ return true;
> >>+ }
> >>+ if (clp->cl_state == NFSD4_EXPIRABLE) {
> >>+ spin_unlock(&clp->cl_cs_lock);
> >>+ return false;
> >>+ }
> >>+ ret = NFSD4_COURTESY ==
> >>+ cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_ACTIVE);
> >>+ spin_unlock(&clp->cl_cs_lock);
> >>+ return ret;
> >>+}
> >--b.
On Sat, Apr 23, 2022 at 11:44:09AM -0700, Dai Ngo wrote:
> This patch provides courteous server support for delegation only.
> Only expired client with delegation but no conflict and no open
> or lock state is allowed to be in COURTESY state.
>
> Delegation conflict with COURTESY client is resolved by setting it
> to EXPIRABLE, queue work for the laundromat and return delay to
> caller. Conflict is resolved when the laudromat runs and expires
> the EXIRABLE client while the NFS client retries the OPEN request.
> Local thread request that gets conflict is doing the retry in
> __break_lease.
>
> Client in COURTESY state is allowed to reconnect and continues to
> have access to its state while client in EXPIRABLE state is not.
> To prevent 2 clients with the same name are on the conf_name_tree,
> nfsd4_setclientid is modified to expire confirmed client in EXPIRABLE
> state.
>
> The spinlock cl_cs_lock is used to handle race conditions between
> conflict resolver, nfsd_break_deleg_cb, and the COURTESY client
> doing reconnect.
>
> find_in_sessionid_hashtbl, find_confirmed_client_by_name and
> find_confirmed_client are modified to activate COURTESY client by
> setting it to ACTIVE state and skip client in EXPIRABLE state.
>
> Signed-off-by: Dai Ngo <[email protected]>
> ---
> fs/nfsd/nfs4state.c | 129 +++++++++++++++++++++++++++++++++++++++++++++-------
> fs/nfsd/nfsd.h | 1 +
> fs/nfsd/state.h | 63 +++++++++++++++++++++++++
> 3 files changed, 177 insertions(+), 16 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 234e852fcdfa..fea5e24e7d94 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
> static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
> static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
>
> +static struct workqueue_struct *laundry_wq;
> +
> static bool is_session_dead(struct nfsd4_session *ses)
> {
> return ses->se_flags & NFS4_SESSION_DEAD;
> @@ -690,6 +692,14 @@ static unsigned int file_hashval(struct svc_fh *fh)
>
> static struct hlist_head file_hashtbl[FILE_HASH_SIZE];
>
> +static inline void
> +run_laundromat(struct nfsd_net *nn, bool wait)
> +{
> + mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
> + if (wait)
> + flush_workqueue(laundry_wq);
> +}
Let's keep those two things separate. The "wait" argument isn't
self-documenting when reading the calling code. And the
mod_delayed_work call isn't always needed before flush_workqueue.
> +
> static void
> __nfs4_file_get_access(struct nfs4_file *fp, u32 access)
> {
> @@ -1939,6 +1949,11 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
> session = __find_in_sessionid_hashtbl(sessionid, net);
> if (!session)
> goto out;
> + if (!try_to_activate_client(session->se_client)) {
> + /* client is EXPIRABLE */
> + session = NULL;
> + goto out;
No, we definitely don't want to do this. As I said before, an
"expirable client" should be treated in every way exactly like any
regular active client. Literally the only difference is that the
laundromat can try to expire it.
And then all this code becomes unnecessary:
> @@ -702,4 +727,42 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
> extern int nfsd4_client_record_check(struct nfs4_client *clp);
> extern void nfsd4_record_grace_done(struct nfsd_net *nn);
>
> +static inline bool try_to_expire_client(struct nfs4_client *clp)
> +{
> + bool ret;
> +
> + spin_lock(&clp->cl_cs_lock);
> + if (clp->cl_state == NFSD4_EXPIRABLE) {
> + spin_unlock(&clp->cl_cs_lock);
> + return true;
> + }
> + ret = NFSD4_COURTESY ==
> + cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
> + spin_unlock(&clp->cl_cs_lock);
> + return ret;
> +}
> +
> +static inline bool try_to_activate_client(struct nfs4_client *clp)
> +{
> + bool ret;
> + struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
> +
> + /* sync with laundromat */
> + lockdep_assert_held(&nn->client_lock);
> +
> + /* sync with try_to_expire_client */
> + spin_lock(&clp->cl_cs_lock);
> + if (clp->cl_state == NFSD4_ACTIVE) {
> + spin_unlock(&clp->cl_cs_lock);
> + return true;
> + }
> + if (clp->cl_state == NFSD4_EXPIRABLE) {
> + spin_unlock(&clp->cl_cs_lock);
> + return false;
> + }
> + ret = NFSD4_COURTESY ==
> + cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_ACTIVE);
> + spin_unlock(&clp->cl_cs_lock);
> + return ret;
> +}
--b.
On Mon, Apr 25, 2022 at 02:35:27PM -0700, [email protected] wrote:
> On 4/25/22 1:40 PM, J. Bruce Fields wrote:
> >On Mon, Apr 25, 2022 at 12:42:58PM -0700, [email protected] wrote:
> >>static inline bool try_to_expire_client(struct nfs4_client *clp)
> >>{
> >> bool ret;
> >>
> >> spin_lock(&clp->cl_cs_lock);
> >> if (clp->cl_state == NFSD4_EXPIRABLE) {
> >> spin_unlock(&clp->cl_cs_lock);
> >> return false; <<<====== was true
> >> }
> >> ret = NFSD4_COURTESY ==
> >> cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
> >> spin_unlock(&clp->cl_cs_lock);
> >> return ret;
> >>}
> >So, try_to_expire_client(), as I said, should be just
> >
> > static bool try_to_expire_client(struct nfs4_client *clp)
> > {
> > return COURTESY == cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
> > }
> >
> >Except, OK, I did forget that somebody else could have already set
> >EXPIRABLE, and we still want to tell the caller to retry in that case,
> >so, oops, let's make it:
> >
> > return ACTIVE != cmpxchg(clp->cl_state, COURTESY, EXPIRABLE);
>
> So functionally this is the same as what i have in the patch, except this
> makes it simpler?
Right.
And my main complaint is still about the code that fails lookups of
EXPIRABLE clients. We shouldn't need to modify find_in_sessionid_hastbl
or other client lookups.
> Do we need to make any change in try_to_activate_client to work with
> this change in try_to_expire_client?
>
> >
> >In other words: set EXPIRABLE if and only if the state is COURTESY, and
> >then tell the caller to retry the operation if and only if the state was
> >previously COURTESY or EXPIRABLE.
> >
> >But we shouldn't need the cl_cs_lock,
>
> The cl_cs_lock is to synchronize between COURTESY client trying to
> reconnect (try_to_activate_client) and another thread is trying to
> resolve a delegation/share/lock conflict (try_to_expire_client).
> So you don't think this is necessary?
Correct, it's not necessary.
The only synchronization is provided by mark_client_expired_locked and
get_client_locked.
We don't need try_to_activate_client. Just set cl_state to ACTIVE in
get_client_locked.
--b.