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From: "J. Bruce Fields" <bfields@redhat.com>
To: linux-nfs@vger.kernel.org
Cc: "J. Bruce Fields" <bfields@redhat.com>
Subject: [PATCH 14/16] nfsd: allow forced expiration of NFSv4 clients
Date: Thu, 20 Jun 2019 10:51:13 -0400
Message-ID: <1561042275-12723-15-git-send-email-bfields@redhat.com> (raw)
In-Reply-To: <1561042275-12723-1-git-send-email-bfields@redhat.com>

From: "J. Bruce Fields" <bfields@redhat.com>

NFSv4 clients are automatically expired and all their locks removed if
they don't contact the server for a certain amount of time (the lease
period, 90 seconds by default).

There can still be situations where that's not enough, so allow
userspace to force expiry by writing "expire\n" to the new
nfsd/client/#/ctl file.

(The generic "ctl" name is because I expect we may want to allow other
operations on clients in the future.)

The write will not return until the client is expired and all of its
locks and other state removed.

The fault injection code also provides a way of expiring clients, but it
fails if there are any in-progress RPC's referencing the client.  Also,
its method of selecting a client to expire is a little more
primitive--it uses an IP address, which can't always uniquely specify an
NFSv4 client.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs4state.c | 70 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 69 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 63f6b87e178e..12e370e62453 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -100,6 +100,13 @@ enum nfsd4_st_mutex_lock_subclass {
  */
 static DECLARE_WAIT_QUEUE_HEAD(close_wq);
 
+/*
+ * A waitqueue where a writer to clients/#/ctl destroying a client can
+ * wait for cl_rpc_users to drop to 0 and then for the client to be
+ * unhashed.
+ */
+static DECLARE_WAIT_QUEUE_HEAD(expiry_wq);
+
 static struct kmem_cache *client_slab;
 static struct kmem_cache *openowner_slab;
 static struct kmem_cache *lockowner_slab;
@@ -175,6 +182,8 @@ static void put_client_renew_locked(struct nfs4_client *clp)
 		return;
 	if (!is_client_expired(clp))
 		renew_client_locked(clp);
+	else
+		wake_up_all(&expiry_wq);
 }
 
 static void put_client_renew(struct nfs4_client *clp)
@@ -185,6 +194,8 @@ static void put_client_renew(struct nfs4_client *clp)
 		return;
 	if (!is_client_expired(clp))
 		renew_client_locked(clp);
+	else
+		wake_up_all(&expiry_wq);
 	spin_unlock(&nn->client_lock);
 }
 
@@ -1910,8 +1921,11 @@ free_client(struct nfs4_client *clp)
 		free_session(ses);
 	}
 	rpc_destroy_wait_queue(&clp->cl_cb_waitq);
-	if (clp->cl_nfsd_dentry)
+	if (clp->cl_nfsd_dentry) {
 		nfsd_client_rmdir(clp->cl_nfsd_dentry);
+		clp->cl_nfsd_dentry = NULL;
+		wake_up_all(&expiry_wq);
+	}
 	drop_client(clp);
 }
 
@@ -2006,6 +2020,7 @@ __destroy_client(struct nfs4_client *clp)
 	if (clp->cl_cb_conn.cb_xprt)
 		svc_xprt_put(clp->cl_cb_conn.cb_xprt);
 	free_client(clp);
+	wake_up_all(&expiry_wq);
 }
 
 static void
@@ -2484,9 +2499,62 @@ static const struct file_operations client_states_fops = {
 	.release	= client_opens_release,
 };
 
+/*
+ * Normally we refuse to destroy clients that are in use, but here the
+ * administrator is telling us to just do it.  We also want to wait
+ * so the caller has a guarantee that the client's locks are gone by
+ * the time the write returns:
+ */
+void force_expire_client(struct nfs4_client *clp)
+{
+	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
+	bool already_expired;
+
+	spin_lock(&clp->cl_lock);
+	clp->cl_time = 0;
+	spin_unlock(&clp->cl_lock);
+
+	wait_event(expiry_wq, atomic_read(&clp->cl_rpc_users) == 0);
+	spin_lock(&nn->client_lock);
+	already_expired = list_empty(&clp->cl_lru);
+	if (!already_expired)
+		unhash_client_locked(clp);
+	spin_unlock(&nn->client_lock);
+
+	if (!already_expired)
+		expire_client(clp);
+	else
+		wait_event(expiry_wq, clp->cl_nfsd_dentry == NULL);
+}
+
+static ssize_t client_ctl_write(struct file *file, const char __user *buf,
+				   size_t size, loff_t *pos)
+{
+	char *data;
+	struct nfs4_client *clp;
+
+	data = simple_transaction_get(file, buf, size);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+	if (size != 7 || 0 != memcmp(data, "expire\n", 7))
+		return -EINVAL;
+	clp = get_nfsdfs_clp(file_inode(file));
+	if (!clp)
+		return -ENXIO;
+	force_expire_client(clp);
+	drop_client(clp);
+	return 7;
+}
+
+static const struct file_operations client_ctl_fops = {
+	.write		= client_ctl_write,
+	.release	= simple_transaction_release,
+};
+
 static const struct tree_descr client_files[] = {
 	[0] = {"info", &client_info_fops, S_IRUSR},
 	[1] = {"states", &client_states_fops, S_IRUSR},
+	[2] = {"ctl", &client_ctl_fops, S_IRUSR|S_IWUSR},
 	[3] = {""},
 };
 
-- 
2.21.0


  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-20 14:50 [PATCH 00/16] exposing knfsd client state to userspace J. Bruce Fields
2019-06-20 14:51 ` [PATCH 01/16] nfsd: persist nfsd filesystem across mounts J. Bruce Fields
2019-06-20 14:51 ` [PATCH 02/16] nfsd: rename cl_refcount J. Bruce Fields
2019-06-20 14:51 ` [PATCH 03/16] nfsd4: use reference count to free client J. Bruce Fields
2019-06-20 14:51 ` [PATCH 04/16] nfsd: add nfsd/clients directory J. Bruce Fields
2019-06-20 14:51 ` [PATCH 05/16] nfsd: make client/ directory names small ints J. Bruce Fields
2019-06-20 14:51 ` [PATCH 06/16] nfsd4: add a client info file J. Bruce Fields
2019-06-20 14:51 ` [PATCH 07/16] nfsd: copy client's address including port number to cl_addr J. Bruce Fields
2019-06-20 14:51 ` [PATCH 08/16] nfsd: escape high characters in binary data J. Bruce Fields
2019-06-21 17:45   ` bfields
2019-06-21 22:26     ` Kees Cook
2019-06-22 19:00       ` J. Bruce Fields
2019-06-22 20:22         ` Kees Cook
2019-06-24 21:05           ` J. Bruce Fields
2019-06-26 16:21             ` J. Bruce Fields
2019-06-27  4:16               ` Kees Cook
2019-06-27 15:23                 ` J. Bruce Fields
2019-06-27 20:21               ` J. Bruce Fields
2019-06-28  3:58                 ` Kees Cook
2019-06-28 16:33                   ` J. Bruce Fields
2019-07-10 22:09                     ` J. Bruce Fields
2019-07-11  1:54                       ` Kees Cook
2019-08-06 12:19   ` Andy Shevchenko
2019-08-06 18:50     ` J. Bruce Fields
2019-08-07  9:00       ` Andy Shevchenko
2019-08-08 11:28         ` bfields
2019-08-27 13:36           ` Andy Shevchenko
2019-06-20 14:51 ` [PATCH 09/16] nfsd: add more information to client info file J. Bruce Fields
2019-06-20 14:51 ` [PATCH 10/16] nfsd4: add file to display list of client's opens J. Bruce Fields
2019-06-20 14:51 ` [PATCH 11/16] nfsd: show lock and deleg stateids J. Bruce Fields
2019-06-20 14:51 ` [PATCH 12/16] nfsd4: show layout stateids J. Bruce Fields
2019-06-20 14:51 ` [PATCH 13/16] nfsd: create get_nfsdfs_clp helper J. Bruce Fields
2019-06-20 14:51 ` J. Bruce Fields [this message]
2019-06-20 14:51 ` [PATCH 15/16] nfsd: create xdr_netobj_dup helper J. Bruce Fields
2019-06-20 14:51 ` [PATCH 16/16] nfsd: decode implementation id J. Bruce Fields
2019-06-21 18:13 ` [PATCH 00/16] exposing knfsd client state to userspace bfields
2019-06-21 19:25   ` Anna Schumaker
2019-06-21 22:08     ` J. Bruce Fields

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