[PATCH RFC v9 0/2] nfsd: Initial implementation of NFSv4 Courteous Server

[PATCH RFC v9 0/2] nfsd: Initial implementation of NFSv4 Courteous Server

[Dai Ngo]

Hi Bruce, Chuck

This series of patches implement the NFSv4 Courteous Server.

A server which does not immediately expunge the state on lease expiration
is known as a Courteous Server.  A Courteous Server continues to recognize
previously generated state tokens as valid until conflict arises between
the expired state and the requests from another client, or the server
reboots.

The v2 patch includes the following:

. add new callback, lm_expire_lock, to lock_manager_operations to
  allow the lock manager to take appropriate action with conflict lock.

. handle conflicts of NFSv4 locks with NFSv3/NLM and local locks.

. expire courtesy client after 24hr if client has not reconnected.

. do not allow expired client to become courtesy client if there are
  waiters for client's locks.

. modify client_info_show to show courtesy client and seconds from
  last renew.

. fix a problem with NFSv4.1 server where the it keeps returning
  SEQ4_STATUS_CB_PATH_DOWN in the successful SEQUENCE reply, after
  the courtesy client re-connects, causing the client to keep sending
  BCTS requests to server.

The v3 patch includes the following:

. modified posix_test_lock to check and resolve conflict locks
  to handle NLM TEST and NFSv4 LOCKT requests.

. separate out fix for back channel stuck in SEQ4_STATUS_CB_PATH_DOWN.

The v4 patch includes:

. rework nfsd_check_courtesy to avoid dead lock of fl_lock and client_lock
  by asking the laudromat thread to destroy the courtesy client.

. handle NFSv4 share reservation conflicts with courtesy client. This
  includes conflicts between access mode and deny mode and vice versa.

. drop the patch for back channel stuck in SEQ4_STATUS_CB_PATH_DOWN.

The v5 patch includes:

. fix recursive locking of file_rwsem from posix_lock_file. 

. retest with LOCKDEP enabled.

The v6 patch includes:

. merge witn 5.15-rc7

. fix a bug in nfs4_check_deny_bmap that did not check for matched
  nfs4_file before checking for access/deny conflict. This bug causes
  pynfs OPEN18 to fail since the server taking too long to release
  lots of un-conflict clients' state.

. enhance share reservation conflict handler to handle case where
  a large number of conflict courtesy clients need to be expired.
  The 1st 100 clients are expired synchronously and the rest are
  expired in the background by the laundromat and NFS4ERR_DELAY
  is returned to the NFS client. This is needed to prevent the
  NFS client from timing out waiting got the reply.

The v7 patch includes:

. Fix race condition in posix_test_lock and posix_lock_inode after
  dropping spinlock.

. Enhance nfsd4_fl_expire_lock to work with with new lm_expire_lock
  callback

. Always resolve share reservation conflicts asynchrously.

. Fix bug in nfs4_laundromat where spinlock is not used when
  scanning cl_ownerstr_hashtbl.

. Fix bug in nfs4_laundromat where idr_get_next was called
  with incorrect 'id'. 

. Merge nfs4_destroy_courtesy_client into nfsd4_fl_expire_lock.

The v8 patch includes:

. Fix warning in nfsd4_fl_expire_lock reported by test robot.

The V9 patch include:

. Simplify lm_expire_lock API by (1) remove the 'testonly' flag
  and (2) specifying return value as true/false to indicate
  whether conflict was succesfully resolved.

. Rework nfsd4_fl_expire_lock to mark client with
  NFSD4_DESTROY_COURTESY_CLIENT then tell the laundromat to expire
  the client in the background.

. Add a spinlock in nfs4_client to synchronize access to the
  NFSD4_COURTESY_CLIENT and NFSD4_DESTROY_COURTESY_CLIENT flag to
  handle race conditions when resolving lock and share reservation
  conflict.

. Courtesy client that was marked as NFSD4_DESTROY_COURTESY_CLIENT
  are now consisdered 'dead', waiting for the laundromat to expire
  it. This client is no longer allowed to use its states if it
  re-connects before the laundromat finishes expiring the client.

  For v4.1 client, the detection is done in the processing of the
  SEQUENCE op and returns NFS4ERR_BAD_SESSION to force the client
  to re-establish new clientid and session.
  For v4.0 client, the detection is done in the processing of the
  RENEW and state-related ops and return NFS4ERR_EXPIRE to force
  the client to re-establish new clientid.

[PATCH RFC v9 1/2] fs/lock: add new callback, lm_expire_lock, to lock_manager_operations

[Dai Ngo]

Add new callback, lm_expire_lock, to lock_manager_operations to allow
the lock manager to take appropriate action to resolve the lock conflict
if possible. The callback takes 1 argument, the file_lock of the blocker
and returns true if the conflict was resolved else returns false. Note
that the lock manager has to be able to resolve the conflict while
the spinlock flc_lock is held.

Lock manager, such as NFSv4 courteous server, uses this callback to
resolve conflict by destroying lock owner, or the NFSv4 courtesy client
(client that has expired but allowed to maintains its states) that owns
the lock.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 fs/locks.c         | 14 ++++++++++----
 include/linux/fs.h |  1 +
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 3d6fb4ae847b..5844fd29560d 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -963,10 +963,13 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 
 	spin_lock(&ctx->flc_lock);
 	list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
-		if (posix_locks_conflict(fl, cfl)) {
-			locks_copy_conflock(fl, cfl);
-			goto out;
-		}
+		if (!posix_locks_conflict(fl, cfl))
+			continue;
+		if (cfl->fl_lmops && cfl->fl_lmops->lm_expire_lock &&
+			cfl->fl_lmops->lm_expire_lock(cfl))
+			continue;
+		locks_copy_conflock(fl, cfl);
+		goto out;
 	}
 	fl->fl_type = F_UNLCK;
 out:
@@ -1169,6 +1172,9 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request,
 		list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
 			if (!posix_locks_conflict(request, fl))
 				continue;
+			if (fl->fl_lmops && fl->fl_lmops->lm_expire_lock &&
+				fl->fl_lmops->lm_expire_lock(fl))
+				continue;
 			if (conflock)
 				locks_copy_conflock(conflock, fl);
 			error = -EAGAIN;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e7a633353fd2..0f70e0b39834 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1071,6 +1071,7 @@ struct lock_manager_operations {
 	int (*lm_change)(struct file_lock *, int, struct list_head *);
 	void (*lm_setup)(struct file_lock *, void **);
 	bool (*lm_breaker_owns_lease)(struct file_lock *);
+	bool (*lm_expire_lock)(struct file_lock *cfl);
 };
 
 struct lock_manager {
-- 
2.9.5

[PATCH RFC v9 2/2] nfsd: Initial implementation of NFSv4 Courteous Server

[Dai Ngo]

Currently an NFSv4 client must maintain its lease by using the at least
one of the state tokens or if nothing else, by issuing a RENEW (4.0), or
a singleton SEQUENCE (4.1) at least once during each lease period. If the
client fails to renew the lease, for any reason, the Linux server expunges
the state tokens immediately upon detection of the "failure to renew the
lease" condition and begins returning NFS4ERR_EXPIRED if the client should
reconnect and attempt to use the (now) expired state.

The default lease period for the Linux server is 90 seconds.  The typical
client cuts that in half and will issue a lease renewing operation every
45 seconds. The 90 second lease period is very short considering the
potential for moderately long term network partitions.  A network partition
refers to any loss of network connectivity between the NFS client and the
NFS server, regardless of its root cause.  This includes NIC failures, NIC
driver bugs, network misconfigurations & administrative errors, routers &
switches crashing and/or having software updates applied, even down to
cables being physically pulled.  In most cases, these network failures are
transient, although the duration is unknown.

A server which does not immediately expunge the state on lease expiration
is known as a Courteous Server.  A Courteous Server continues to recognize
previously generated state tokens as valid until conflict arises between
the expired state and the requests from another client, or the server
reboots.

The initial implementation of the Courteous Server will do the following:

. when the laundromat thread detects an expired client and if that client
still has established states on the Linux server and there is no waiters
for the client's locks then mark the client as a COURTESY_CLIENT and skip
destroying the client and all its states, otherwise destroy the client as
usual.

. detects conflict of OPEN request with COURTESY_CLIENT, destroys the
expired client and all its states, skips the delegation recall then allows
the conflicting request to succeed.

. detects conflict of LOCK/LOCKT, NLM LOCK and TEST, and local locks
requests with COURTESY_CLIENT, destroys the expired client and all its
states then allows the conflicting request to succeed.

. detects conflict of LOCK/LOCKT, NLM LOCK and TEST, and local locks
requests with COURTESY_CLIENT, destroys the expired client and all its
states then allows the conflicting request to succeed.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 fs/nfsd/nfs4state.c | 323 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 fs/nfsd/state.h     |   8 ++
 2 files changed, 323 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 3f4027a5de88..e7fa4da44835 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -125,6 +125,11 @@ 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 void laundromat_main(struct work_struct *);
+
+static const int courtesy_client_expiry = (24 * 60 * 60);	/* in secs */
+
 static bool is_session_dead(struct nfsd4_session *ses)
 {
 	return ses->se_flags & NFS4_SESSION_DEAD;
@@ -155,8 +160,10 @@ static __be32 get_client_locked(struct nfs4_client *clp)
 	return nfs_ok;
 }
 
-/* must be called under the client_lock */
+/* must be called under the client_lock
 static inline void
+*/
+void
 renew_client_locked(struct nfs4_client *clp)
 {
 	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
@@ -172,7 +179,9 @@ renew_client_locked(struct nfs4_client *clp)
 
 	list_move_tail(&clp->cl_lru, &nn->client_lru);
 	clp->cl_time = ktime_get_boottime_seconds();
+	clear_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags);
 }
+EXPORT_SYMBOL_GPL(renew_client_locked);
 
 static void put_client_renew_locked(struct nfs4_client *clp)
 {
@@ -1912,10 +1921,22 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
 {
 	struct nfsd4_session *session;
 	__be32 status = nfserr_badsession;
+	struct nfs4_client *clp;
 
 	session = __find_in_sessionid_hashtbl(sessionid, net);
 	if (!session)
 		goto out;
+	clp = session->se_client;
+	if (clp) {
+		spin_lock(&clp->cl_cs_lock);
+		if (test_bit(NFSD4_DESTROY_COURTESY_CLIENT, &clp->cl_flags)) {
+			spin_unlock(&clp->cl_cs_lock);
+			session = NULL;
+			goto out;
+		}
+		clear_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags);
+		spin_unlock(&clp->cl_cs_lock);
+	}
 	status = nfsd4_get_session_locked(session);
 	if (status)
 		session = NULL;
@@ -1992,6 +2013,7 @@ 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:
@@ -2389,6 +2411,10 @@ static int client_info_show(struct seq_file *m, void *v)
 		seq_puts(m, "status: confirmed\n");
 	else
 		seq_puts(m, "status: unconfirmed\n");
+	seq_printf(m, "courtesy client: %s\n",
+		test_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags) ? "yes" : "no");
+	seq_printf(m, "seconds from last renew: %lld\n",
+		ktime_get_boottime_seconds() - clp->cl_time);
 	seq_printf(m, "name: ");
 	seq_quote_mem(m, clp->cl_name.data, clp->cl_name.len);
 	seq_printf(m, "\nminor version: %d\n", clp->cl_minorversion);
@@ -2809,8 +2835,17 @@ find_clp_in_name_tree(struct xdr_netobj *name, struct rb_root *root)
 			node = node->rb_left;
 		else if (cmp < 0)
 			node = node->rb_right;
-		else
-			return clp;
+		else {
+			spin_lock(&clp->cl_cs_lock);
+			if (!test_bit(NFSD4_DESTROY_COURTESY_CLIENT,
+					&clp->cl_flags)) {
+				clear_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags);
+				spin_unlock(&clp->cl_cs_lock);
+				return clp;
+			}
+			spin_unlock(&clp->cl_cs_lock);
+			return NULL;
+		}
 	}
 	return NULL;
 }
@@ -2856,6 +2891,14 @@ find_client_in_id_table(struct list_head *tbl, clientid_t *clid, bool sessions)
 		if (same_clid(&clp->cl_clientid, clid)) {
 			if ((bool)clp->cl_minorversion != sessions)
 				return NULL;
+			spin_lock(&clp->cl_cs_lock);
+			if (test_bit(NFSD4_DESTROY_COURTESY_CLIENT,
+					&clp->cl_flags)) {
+				spin_unlock(&clp->cl_cs_lock);
+				continue;
+			}
+			clear_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags);
+			spin_unlock(&clp->cl_cs_lock);
 			renew_client_locked(clp);
 			return clp;
 		}
@@ -4662,6 +4705,36 @@ static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
 	nfsd4_run_cb(&dp->dl_recall);
 }
 
+/*
+ * This function is called when a file is opened and there is a
+ * delegation conflict with another client. If the other client
+ * is a courtesy client then kick start the laundromat to destroy
+ * it.
+ */
+static bool
+nfsd_check_courtesy_client(struct nfs4_delegation *dp)
+{
+	struct svc_rqst *rqst;
+	struct nfs4_client *clp = dp->dl_recall.cb_clp;
+	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
+
+	if (!i_am_nfsd())
+		goto out;
+	rqst = kthread_data(current);
+	if (rqst->rq_prog != NFS_PROGRAM || rqst->rq_vers < 4)
+		return false;
+out:
+	spin_lock(&clp->cl_cs_lock);
+	if (test_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags)) {
+		set_bit(NFSD4_DESTROY_COURTESY_CLIENT, &clp->cl_flags);
+		spin_unlock(&clp->cl_cs_lock);
+		mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
+		return true;
+	}
+	spin_unlock(&clp->cl_cs_lock);
+	return false;
+}
+
 /* Called from break_lease() with i_lock held. */
 static bool
 nfsd_break_deleg_cb(struct file_lock *fl)
@@ -4670,6 +4743,8 @@ nfsd_break_deleg_cb(struct file_lock *fl)
 	struct nfs4_delegation *dp = (struct nfs4_delegation *)fl->fl_owner;
 	struct nfs4_file *fp = dp->dl_stid.sc_file;
 
+	if (nfsd_check_courtesy_client(dp))
+		return false;
 	trace_nfsd_cb_recall(&dp->dl_stid);
 
 	/*
@@ -4912,7 +4987,128 @@ nfsd4_truncate(struct svc_rqst *rqstp, struct svc_fh *fh,
 	return nfsd_setattr(rqstp, fh, &iattr, 0, (time64_t)0);
 }
 
-static __be32 nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
+static bool
+__nfs4_check_access_deny_bmap(struct nfs4_ol_stateid *stp, u32 access,
+			bool share_access)
+{
+	if (share_access) {
+		if (!stp->st_deny_bmap)
+			return false;
+
+		if ((stp->st_deny_bmap & (1 << NFS4_SHARE_DENY_BOTH)) ||
+			(access & NFS4_SHARE_ACCESS_READ &&
+				stp->st_deny_bmap & (1 << NFS4_SHARE_DENY_READ)) ||
+			(access & NFS4_SHARE_ACCESS_WRITE &&
+				stp->st_deny_bmap & (1 << NFS4_SHARE_DENY_WRITE))) {
+			return true;
+		}
+		return false;
+	}
+	if ((access & NFS4_SHARE_DENY_BOTH) ||
+		(access & NFS4_SHARE_DENY_READ &&
+			stp->st_access_bmap & (1 << NFS4_SHARE_ACCESS_READ)) ||
+		(access & NFS4_SHARE_DENY_WRITE &&
+			stp->st_access_bmap & (1 << NFS4_SHARE_ACCESS_WRITE))) {
+		return true;
+	}
+	return false;
+}
+
+/*
+ * Check all files belong to the specified client to determine if there is
+ * any conflict with the specified access_mode/deny_mode of the file 'fp.
+ *
+ * If share_access is true then 'access' is the access mode. Check if
+ * this access mode conflicts with current deny mode of the file.
+ *
+ * If share_access is false then 'access' the deny mode. Check if
+ * this deny mode conflicts with current access mode of the file.
+ */
+static bool
+nfs4_check_access_deny_bmap(struct nfs4_client *clp, struct nfs4_file *fp,
+		struct nfs4_ol_stateid *st, u32 access, bool share_access)
+{
+	int i;
+	struct nfs4_openowner *oo;
+	struct nfs4_stateowner *so, *tmp;
+	struct nfs4_ol_stateid *stp, *stmp;
+
+	spin_lock(&clp->cl_lock);
+	for (i = 0; i < OWNER_HASH_SIZE; i++) {
+		list_for_each_entry_safe(so, tmp, &clp->cl_ownerstr_hashtbl[i],
+					so_strhash) {
+			if (!so->so_is_open_owner)
+				continue;
+			oo = openowner(so);
+			list_for_each_entry_safe(stp, stmp,
+				&oo->oo_owner.so_stateids, st_perstateowner) {
+				if (stp == st || stp->st_stid.sc_file != fp)
+					continue;
+				if (__nfs4_check_access_deny_bmap(stp, access,
+							share_access)) {
+					spin_unlock(&clp->cl_lock);
+					return true;
+				}
+			}
+		}
+	}
+	spin_unlock(&clp->cl_lock);
+	return false;
+}
+
+/*
+ * This function is called to check whether nfserr_share_denied should
+ * be returning to client.
+ *
+ * access: is op_share_access if share_access is true.
+ *	   Check if access mode, op_share_access, would conflict with
+ *	   the current deny mode of the file 'fp'.
+ * access: is op_share_deny if share_access is true.
+ *	   Check if the deny mode, op_share_deny, would conflict with
+ *	   current access of the file 'fp'.
+ * stp:    skip checking this entry.
+ *
+ * Function returns:
+ *	true  - access/deny mode conflict with courtesy client(s).
+ *		Caller to return nfserr_jukebox while client(s) being expired.
+ *	false - access/deny mode conflict with non-courtesy client.
+ *		Caller to return nfserr_share_denied to client.
+ */
+static bool
+nfs4_conflict_courtesy_clients(struct svc_rqst *rqstp, struct nfs4_file *fp,
+		struct nfs4_ol_stateid *stp, u32 access, bool share_access)
+{
+	struct nfs4_client *cl;
+	bool conflict = false;
+	int async_cnt = 0;
+	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+
+	spin_lock(&nn->client_lock);
+	list_for_each_entry(cl, &nn->client_lru, cl_lru) {
+		if (!nfs4_check_access_deny_bmap(cl, fp, stp, access, share_access))
+			continue;
+		spin_lock(&cl->cl_cs_lock);
+		if (test_bit(NFSD4_COURTESY_CLIENT, &cl->cl_flags)) {
+			set_bit(NFSD4_DESTROY_COURTESY_CLIENT, &cl->cl_flags);
+			async_cnt++;
+			spin_unlock(&cl->cl_cs_lock);
+			continue;
+		}
+		/* conflict with non-courtesy client */
+		spin_unlock(&cl->cl_cs_lock);
+		conflict = false;
+		break;
+	}
+	spin_unlock(&nn->client_lock);
+	if (async_cnt) {
+		mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
+		conflict = true;
+	}
+	return conflict;
+}
+
+static __be32
+nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
 		struct svc_fh *cur_fh, struct nfs4_ol_stateid *stp,
 		struct nfsd4_open *open)
 {
@@ -4931,6 +5127,11 @@ static __be32 nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
 	status = nfs4_file_check_deny(fp, open->op_share_deny);
 	if (status != nfs_ok) {
 		spin_unlock(&fp->fi_lock);
+		if (status != nfserr_share_denied)
+			goto out;
+		if (nfs4_conflict_courtesy_clients(rqstp, fp,
+				stp, open->op_share_deny, false))
+			status = nfserr_jukebox;
 		goto out;
 	}
 
@@ -4938,6 +5139,11 @@ static __be32 nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
 	status = nfs4_file_get_access(fp, open->op_share_access);
 	if (status != nfs_ok) {
 		spin_unlock(&fp->fi_lock);
+		if (status != nfserr_share_denied)
+			goto out;
+		if (nfs4_conflict_courtesy_clients(rqstp, fp,
+				stp, open->op_share_access, true))
+			status = nfserr_jukebox;
 		goto out;
 	}
 
@@ -5572,6 +5778,47 @@ static void nfsd4_ssc_expire_umount(struct nfsd_net *nn)
 }
 #endif
 
+static
+bool nfs4_anylock_conflict(struct nfs4_client *clp)
+{
+	int i;
+	struct nfs4_stateowner *so, *tmp;
+	struct nfs4_lockowner *lo;
+	struct nfs4_ol_stateid *stp;
+	struct nfs4_file *nf;
+	struct inode *ino;
+	struct file_lock_context *ctx;
+	struct file_lock *fl;
+
+	for (i = 0; i < OWNER_HASH_SIZE; i++) {
+		/* scan each lock owner */
+		list_for_each_entry_safe(so, tmp, &clp->cl_ownerstr_hashtbl[i],
+				so_strhash) {
+			if (so->so_is_open_owner)
+				continue;
+
+			/* scan lock states of this lock owner */
+			lo = lockowner(so);
+			list_for_each_entry(stp, &lo->lo_owner.so_stateids,
+					st_perstateowner) {
+				nf = stp->st_stid.sc_file;
+				ino = nf->fi_inode;
+				ctx = ino->i_flctx;
+				if (!ctx)
+					continue;
+				/* check each lock belongs to this lock state */
+				list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
+					if (fl->fl_owner != lo)
+						continue;
+					if (!list_empty(&fl->fl_blocked_requests))
+						return true;
+				}
+			}
+		}
+	}
+	return false;
+}
+
 static time64_t
 nfs4_laundromat(struct nfsd_net *nn)
 {
@@ -5587,7 +5834,9 @@ nfs4_laundromat(struct nfsd_net *nn)
 	};
 	struct nfs4_cpntf_state *cps;
 	copy_stateid_t *cps_t;
+	struct nfs4_stid *stid;
 	int i;
+	int id;
 
 	if (clients_still_reclaiming(nn)) {
 		lt.new_timeo = 0;
@@ -5608,8 +5857,41 @@ nfs4_laundromat(struct nfsd_net *nn)
 	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(&lt, clp->cl_time))
+		spin_lock(&clp->cl_cs_lock);
+		if (test_bit(NFSD4_DESTROY_COURTESY_CLIENT, &clp->cl_flags))
+			goto exp_client;
+		if (test_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags)) {
+			if (ktime_get_boottime_seconds() >= clp->courtesy_client_expiry)
+				goto exp_client;
+			/*
+			 * after umount, v4.0 client is still around
+			 * waiting to be expired. Check again and if
+			 * it has no state then expire it.
+			 */
+			if (clp->cl_minorversion) {
+				spin_unlock(&clp->cl_cs_lock);
+				continue;
+			}
+		}
+		if (!state_expired(&lt, clp->cl_time)) {
+			spin_unlock(&clp->cl_cs_lock);
 			break;
+		}
+		id = 0;
+		spin_lock(&clp->cl_lock);
+		stid = idr_get_next(&clp->cl_stateids, &id);
+		if (stid && !nfs4_anylock_conflict(clp)) {
+			/* client still has states */
+			spin_unlock(&clp->cl_lock);
+			clp->courtesy_client_expiry =
+				ktime_get_boottime_seconds() + courtesy_client_expiry;
+			set_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags);
+			spin_unlock(&clp->cl_cs_lock);
+			continue;
+		}
+		spin_unlock(&clp->cl_lock);
+exp_client:
+		spin_unlock(&clp->cl_cs_lock);
 		if (mark_client_expired_locked(clp))
 			continue;
 		list_add(&clp->cl_lru, &reaplist);
@@ -5689,9 +5971,6 @@ 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
 laundromat_main(struct work_struct *laundry)
 {
@@ -6496,6 +6775,33 @@ nfs4_transform_lock_offset(struct file_lock *lock)
 		lock->fl_end = OFFSET_MAX;
 }
 
+/*
+ * Return true if lock can be resolved by expiring
+ * courtesy client else return false.
+ */
+static bool
+nfsd4_fl_expire_lock(struct file_lock *fl)
+{
+	struct nfs4_lockowner *lo;
+	struct nfs4_client *clp;
+	struct nfsd_net *nn;
+
+	if (!fl)
+		return false;
+	lo = (struct nfs4_lockowner *)fl->fl_owner;
+	clp = lo->lo_owner.so_client;
+	spin_lock(&clp->cl_cs_lock);
+	if (!test_bit(NFSD4_COURTESY_CLIENT, &clp->cl_flags)) {
+		spin_unlock(&clp->cl_cs_lock);
+		return false;
+	}
+	nn = net_generic(clp->net, nfsd_net_id);
+	set_bit(NFSD4_DESTROY_COURTESY_CLIENT, &clp->cl_flags);
+	spin_unlock(&clp->cl_cs_lock);
+	mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
+	return true;
+}
+
 static fl_owner_t
 nfsd4_fl_get_owner(fl_owner_t owner)
 {
@@ -6543,6 +6849,7 @@ static const struct lock_manager_operations nfsd_posix_mng_ops  = {
 	.lm_notify = nfsd4_lm_notify,
 	.lm_get_owner = nfsd4_fl_get_owner,
 	.lm_put_owner = nfsd4_fl_put_owner,
+	.lm_expire_lock = nfsd4_fl_expire_lock,
 };
 
 static inline void
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index e73bdbb1634a..7f52a79e0743 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -345,6 +345,8 @@ struct nfs4_client {
 #define NFSD4_CLIENT_UPCALL_LOCK	(5)	/* upcall serialization */
 #define NFSD4_CLIENT_CB_FLAG_MASK	(1 << NFSD4_CLIENT_CB_UPDATE | \
 					 1 << NFSD4_CLIENT_CB_KILL)
+#define NFSD4_COURTESY_CLIENT		(6)	/* be nice to expired client */
+#define NFSD4_DESTROY_COURTESY_CLIENT	(7)
 	unsigned long		cl_flags;
 	const struct cred	*cl_cb_cred;
 	struct rpc_clnt		*cl_cb_client;
@@ -385,6 +387,12 @@ 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 */
+	int			courtesy_client_expiry;
+	/*
+	 * used to synchronize access to NFSD4_COURTESY_CLIENT
+	 * and NFSD4_DESTROY_COURTESY_CLIENT for race conditions.
+	 */
+	spinlock_t		cl_cs_lock;
 };
 
 /* struct nfs4_client_reset
-- 
2.9.5

[PATCH RFC v9 1/2] fs/lock: add new callback, lm_expire_lock, to lock_manager_operations

[Dai Ngo]

Add new callback, lm_expire_lock, to lock_manager_operations to allow
the lock manager to take appropriate action to resolve the lock conflict
if possible. The callback takes 1 argument, the file_lock of the blocker
and returns true if the conflict was resolved else returns false. Note
that the lock manager has to be able to resolve the conflict while
the spinlock flc_lock is held.

Lock manager, such as NFSv4 courteous server, uses this callback to
resolve conflict by destroying lock owner, or the NFSv4 courtesy client
(client that has expired but allowed to maintains its states) that owns
the lock.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 fs/locks.c         | 14 ++++++++++----
 include/linux/fs.h |  1 +
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 3d6fb4ae847b..5844fd29560d 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -963,10 +963,13 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 
 	spin_lock(&ctx->flc_lock);
 	list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
-		if (posix_locks_conflict(fl, cfl)) {
-			locks_copy_conflock(fl, cfl);
-			goto out;
-		}
+		if (!posix_locks_conflict(fl, cfl))
+			continue;
+		if (cfl->fl_lmops && cfl->fl_lmops->lm_expire_lock &&
+			cfl->fl_lmops->lm_expire_lock(cfl))
+			continue;
+		locks_copy_conflock(fl, cfl);
+		goto out;
 	}
 	fl->fl_type = F_UNLCK;
 out:
@@ -1169,6 +1172,9 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request,
 		list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
 			if (!posix_locks_conflict(request, fl))
 				continue;
+			if (fl->fl_lmops && fl->fl_lmops->lm_expire_lock &&
+				fl->fl_lmops->lm_expire_lock(fl))
+				continue;
 			if (conflock)
 				locks_copy_conflock(conflock, fl);
 			error = -EAGAIN;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e7a633353fd2..0f70e0b39834 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1071,6 +1071,7 @@ struct lock_manager_operations {
 	int (*lm_change)(struct file_lock *, int, struct list_head *);
 	void (*lm_setup)(struct file_lock *, void **);
 	bool (*lm_breaker_owns_lease)(struct file_lock *);
+	bool (*lm_expire_lock)(struct file_lock *cfl);
 };
 
 struct lock_manager {
-- 
2.9.5