Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 884 insertions, 0 deletions

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
new file mode 100644
index 0000000000..fba6c7fa74
--- /dev/null
+++ b/fs/lockd/clntproc.c
@@ -0,0 +1,884 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/fs/lockd/clntproc.c
+ *
+ * RPC procedures for the client side NLM implementation
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/filelock.h>
+#include <linux/nfs_fs.h>
+#include <linux/utsname.h>
+#include <linux/freezer.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/svc.h>
+#include <linux/lockd/lockd.h>
+
+#include "trace.h"
+
+#define NLMDBG_FACILITY		NLMDBG_CLIENT
+#define NLMCLNT_GRACE_WAIT	(5*HZ)
+#define NLMCLNT_POLL_TIMEOUT	(30*HZ)
+#define NLMCLNT_MAX_RETRIES	3
+
+static int	nlmclnt_test(struct nlm_rqst *, struct file_lock *);
+static int	nlmclnt_lock(struct nlm_rqst *, struct file_lock *);
+static int	nlmclnt_unlock(struct nlm_rqst *, struct file_lock *);
+static int	nlm_stat_to_errno(__be32 stat);
+static void	nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host);
+static int	nlmclnt_cancel(struct nlm_host *, int , struct file_lock *);
+
+static const struct rpc_call_ops nlmclnt_unlock_ops;
+static const struct rpc_call_ops nlmclnt_cancel_ops;
+
+/*
+ * Cookie counter for NLM requests
+ */
+static atomic_t	nlm_cookie = ATOMIC_INIT(0x1234);
+
+void nlmclnt_next_cookie(struct nlm_cookie *c)
+{
+	u32	cookie = atomic_inc_return(&nlm_cookie);
+
+	memcpy(c->data, &cookie, 4);
+	c->len=4;
+}
+
+static struct nlm_lockowner *
+nlmclnt_get_lockowner(struct nlm_lockowner *lockowner)
+{
+	refcount_inc(&lockowner->count);
+	return lockowner;
+}
+
+static void nlmclnt_put_lockowner(struct nlm_lockowner *lockowner)
+{
+	if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
+		return;
+	list_del(&lockowner->list);
+	spin_unlock(&lockowner->host->h_lock);
+	nlmclnt_release_host(lockowner->host);
+	kfree(lockowner);
+}
+
+static inline int nlm_pidbusy(struct nlm_host *host, uint32_t pid)
+{
+	struct nlm_lockowner *lockowner;
+	list_for_each_entry(lockowner, &host->h_lockowners, list) {
+		if (lockowner->pid == pid)
+			return -EBUSY;
+	}
+	return 0;
+}
+
+static inline uint32_t __nlm_alloc_pid(struct nlm_host *host)
+{
+	uint32_t res;
+	do {
+		res = host->h_pidcount++;
+	} while (nlm_pidbusy(host, res) < 0);
+	return res;
+}
+
+static struct nlm_lockowner *__nlmclnt_find_lockowner(struct nlm_host *host, fl_owner_t owner)
+{
+	struct nlm_lockowner *lockowner;
+	list_for_each_entry(lockowner, &host->h_lockowners, list) {
+		if (lockowner->owner != owner)
+			continue;
+		return nlmclnt_get_lockowner(lockowner);
+	}
+	return NULL;
+}
+
+static struct nlm_lockowner *nlmclnt_find_lockowner(struct nlm_host *host, fl_owner_t owner)
+{
+	struct nlm_lockowner *res, *new = NULL;
+
+	spin_lock(&host->h_lock);
+	res = __nlmclnt_find_lockowner(host, owner);
+	if (res == NULL) {
+		spin_unlock(&host->h_lock);
+		new = kmalloc(sizeof(*new), GFP_KERNEL);
+		spin_lock(&host->h_lock);
+		res = __nlmclnt_find_lockowner(host, owner);
+		if (res == NULL && new != NULL) {
+			res = new;
+			refcount_set(&new->count, 1);
+			new->owner = owner;
+			new->pid = __nlm_alloc_pid(host);
+			new->host = nlm_get_host(host);
+			list_add(&new->list, &host->h_lockowners);
+			new = NULL;
+		}
+	}
+	spin_unlock(&host->h_lock);
+	kfree(new);
+	return res;
+}
+
+/*
+ * Initialize arguments for TEST/LOCK/UNLOCK/CANCEL calls
+ */
+static void nlmclnt_setlockargs(struct nlm_rqst *req, struct file_lock *fl)
+{
+	struct nlm_args	*argp = &req->a_args;
+	struct nlm_lock	*lock = &argp->lock;
+	char *nodename = req->a_host->h_rpcclnt->cl_nodename;
+
+	nlmclnt_next_cookie(&argp->cookie);
+	memcpy(&lock->fh, NFS_FH(file_inode(fl->fl_file)), sizeof(struct nfs_fh));
+	lock->caller  = nodename;
+	lock->oh.data = req->a_owner;
+	lock->oh.len  = snprintf(req->a_owner, sizeof(req->a_owner), "%u@%s",
+				(unsigned int)fl->fl_u.nfs_fl.owner->pid,
+				nodename);
+	lock->svid = fl->fl_u.nfs_fl.owner->pid;
+	lock->fl.fl_start = fl->fl_start;
+	lock->fl.fl_end = fl->fl_end;
+	lock->fl.fl_type = fl->fl_type;
+}
+
+static void nlmclnt_release_lockargs(struct nlm_rqst *req)
+{
+	WARN_ON_ONCE(req->a_args.lock.fl.fl_ops != NULL);
+}
+
+/**
+ * nlmclnt_proc - Perform a single client-side lock request
+ * @host: address of a valid nlm_host context representing the NLM server
+ * @cmd: fcntl-style file lock operation to perform
+ * @fl: address of arguments for the lock operation
+ * @data: address of data to be sent to callback operations
+ *
+ */
+int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl, void *data)
+{
+	struct nlm_rqst		*call;
+	int			status;
+	const struct nlmclnt_operations *nlmclnt_ops = host->h_nlmclnt_ops;
+
+	call = nlm_alloc_call(host);
+	if (call == NULL)
+		return -ENOMEM;
+
+	if (nlmclnt_ops && nlmclnt_ops->nlmclnt_alloc_call)
+		nlmclnt_ops->nlmclnt_alloc_call(data);
+
+	nlmclnt_locks_init_private(fl, host);
+	if (!fl->fl_u.nfs_fl.owner) {
+		/* lockowner allocation has failed */
+		nlmclnt_release_call(call);
+		return -ENOMEM;
+	}
+	/* Set up the argument struct */
+	nlmclnt_setlockargs(call, fl);
+	call->a_callback_data = data;
+
+	if (IS_SETLK(cmd) || IS_SETLKW(cmd)) {
+		if (fl->fl_type != F_UNLCK) {
+			call->a_args.block = IS_SETLKW(cmd) ? 1 : 0;
+			status = nlmclnt_lock(call, fl);
+		} else
+			status = nlmclnt_unlock(call, fl);
+	} else if (IS_GETLK(cmd))
+		status = nlmclnt_test(call, fl);
+	else
+		status = -EINVAL;
+	fl->fl_ops->fl_release_private(fl);
+	fl->fl_ops = NULL;
+
+	dprintk("lockd: clnt proc returns %d\n", status);
+	return status;
+}
+EXPORT_SYMBOL_GPL(nlmclnt_proc);
+
+/*
+ * Allocate an NLM RPC call struct
+ */
+struct nlm_rqst *nlm_alloc_call(struct nlm_host *host)
+{
+	struct nlm_rqst	*call;
+
+	for(;;) {
+		call = kzalloc(sizeof(*call), GFP_KERNEL);
+		if (call != NULL) {
+			refcount_set(&call->a_count, 1);
+			locks_init_lock(&call->a_args.lock.fl);
+			locks_init_lock(&call->a_res.lock.fl);
+			call->a_host = nlm_get_host(host);
+			return call;
+		}
+		if (signalled())
+			break;
+		printk("nlm_alloc_call: failed, waiting for memory\n");
+		schedule_timeout_interruptible(5*HZ);
+	}
+	return NULL;
+}
+
+void nlmclnt_release_call(struct nlm_rqst *call)
+{
+	const struct nlmclnt_operations *nlmclnt_ops = call->a_host->h_nlmclnt_ops;
+
+	if (!refcount_dec_and_test(&call->a_count))
+		return;
+	if (nlmclnt_ops && nlmclnt_ops->nlmclnt_release_call)
+		nlmclnt_ops->nlmclnt_release_call(call->a_callback_data);
+	nlmclnt_release_host(call->a_host);
+	nlmclnt_release_lockargs(call);
+	kfree(call);
+}
+
+static void nlmclnt_rpc_release(void *data)
+{
+	nlmclnt_release_call(data);
+}
+
+static int nlm_wait_on_grace(wait_queue_head_t *queue)
+{
+	DEFINE_WAIT(wait);
+	int status = -EINTR;
+
+	prepare_to_wait(queue, &wait, TASK_INTERRUPTIBLE);
+	if (!signalled ()) {
+		schedule_timeout(NLMCLNT_GRACE_WAIT);
+		try_to_freeze();
+		if (!signalled ())
+			status = 0;
+	}
+	finish_wait(queue, &wait);
+	return status;
+}
+
+/*
+ * Generic NLM call
+ */
+static int
+nlmclnt_call(const struct cred *cred, struct nlm_rqst *req, u32 proc)
+{
+	struct nlm_host	*host = req->a_host;
+	struct rpc_clnt	*clnt;
+	struct nlm_args	*argp = &req->a_args;
+	struct nlm_res	*resp = &req->a_res;
+	struct rpc_message msg = {
+		.rpc_argp	= argp,
+		.rpc_resp	= resp,
+		.rpc_cred	= cred,
+	};
+	int		status;
+
+	dprintk("lockd: call procedure %d on %s\n",
+			(int)proc, host->h_name);
+
+	do {
+		if (host->h_reclaiming && !argp->reclaim)
+			goto in_grace_period;
+
+		/* If we have no RPC client yet, create one. */
+		if ((clnt = nlm_bind_host(host)) == NULL)
+			return -ENOLCK;
+		msg.rpc_proc = &clnt->cl_procinfo[proc];
+
+		/* Perform the RPC call. If an error occurs, try again */
+		if ((status = rpc_call_sync(clnt, &msg, 0)) < 0) {
+			dprintk("lockd: rpc_call returned error %d\n", -status);
+			switch (status) {
+			case -EPROTONOSUPPORT:
+				status = -EINVAL;
+				break;
+			case -ECONNREFUSED:
+			case -ETIMEDOUT:
+			case -ENOTCONN:
+				nlm_rebind_host(host);
+				status = -EAGAIN;
+				break;
+			case -ERESTARTSYS:
+				return signalled () ? -EINTR : status;
+			default:
+				break;
+			}
+			break;
+		} else
+		if (resp->status == nlm_lck_denied_grace_period) {
+			dprintk("lockd: server in grace period\n");
+			if (argp->reclaim) {
+				printk(KERN_WARNING
+				     "lockd: spurious grace period reject?!\n");
+				return -ENOLCK;
+			}
+		} else {
+			if (!argp->reclaim) {
+				/* We appear to be out of the grace period */
+				wake_up_all(&host->h_gracewait);
+			}
+			dprintk("lockd: server returns status %d\n",
+				ntohl(resp->status));
+			return 0;	/* Okay, call complete */
+		}
+
+in_grace_period:
+		/*
+		 * The server has rebooted and appears to be in the grace
+		 * period during which locks are only allowed to be
+		 * reclaimed.
+		 * We can only back off and try again later.
+		 */
+		status = nlm_wait_on_grace(&host->h_gracewait);
+	} while (status == 0);
+
+	return status;
+}
+
+/*
+ * Generic NLM call, async version.
+ */
+static struct rpc_task *__nlm_async_call(struct nlm_rqst *req, u32 proc, struct rpc_message *msg, const struct rpc_call_ops *tk_ops)
+{
+	struct nlm_host	*host = req->a_host;
+	struct rpc_clnt	*clnt;
+	struct rpc_task_setup task_setup_data = {
+		.rpc_message = msg,
+		.callback_ops = tk_ops,
+		.callback_data = req,
+		.flags = RPC_TASK_ASYNC,
+	};
+
+	dprintk("lockd: call procedure %d on %s (async)\n",
+			(int)proc, host->h_name);
+
+	/* If we have no RPC client yet, create one. */
+	clnt = nlm_bind_host(host);
+	if (clnt == NULL)
+		goto out_err;
+	msg->rpc_proc = &clnt->cl_procinfo[proc];
+	task_setup_data.rpc_client = clnt;
+
+        /* bootstrap and kick off the async RPC call */
+	return rpc_run_task(&task_setup_data);
+out_err:
+	tk_ops->rpc_release(req);
+	return ERR_PTR(-ENOLCK);
+}
+
+static int nlm_do_async_call(struct nlm_rqst *req, u32 proc, struct rpc_message *msg, const struct rpc_call_ops *tk_ops)
+{
+	struct rpc_task *task;
+
+	task = __nlm_async_call(req, proc, msg, tk_ops);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	rpc_put_task(task);
+	return 0;
+}
+
+/*
+ * NLM asynchronous call.
+ */
+int nlm_async_call(struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
+{
+	struct rpc_message msg = {
+		.rpc_argp	= &req->a_args,
+		.rpc_resp	= &req->a_res,
+	};
+	return nlm_do_async_call(req, proc, &msg, tk_ops);
+}
+
+int nlm_async_reply(struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
+{
+	struct rpc_message msg = {
+		.rpc_argp	= &req->a_res,
+	};
+	return nlm_do_async_call(req, proc, &msg, tk_ops);
+}
+
+/*
+ * NLM client asynchronous call.
+ *
+ * Note that although the calls are asynchronous, and are therefore
+ *      guaranteed to complete, we still always attempt to wait for
+ *      completion in order to be able to correctly track the lock
+ *      state.
+ */
+static int nlmclnt_async_call(const struct cred *cred, struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
+{
+	struct rpc_message msg = {
+		.rpc_argp	= &req->a_args,
+		.rpc_resp	= &req->a_res,
+		.rpc_cred	= cred,
+	};
+	struct rpc_task *task;
+	int err;
+
+	task = __nlm_async_call(req, proc, &msg, tk_ops);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	err = rpc_wait_for_completion_task(task);
+	rpc_put_task(task);
+	return err;
+}
+
+/*
+ * TEST for the presence of a conflicting lock
+ */
+static int
+nlmclnt_test(struct nlm_rqst *req, struct file_lock *fl)
+{
+	int	status;
+
+	status = nlmclnt_call(nfs_file_cred(fl->fl_file), req, NLMPROC_TEST);
+	if (status < 0)
+		goto out;
+
+	switch (req->a_res.status) {
+		case nlm_granted:
+			fl->fl_type = F_UNLCK;
+			break;
+		case nlm_lck_denied:
+			/*
+			 * Report the conflicting lock back to the application.
+			 */
+			fl->fl_start = req->a_res.lock.fl.fl_start;
+			fl->fl_end = req->a_res.lock.fl.fl_end;
+			fl->fl_type = req->a_res.lock.fl.fl_type;
+			fl->fl_pid = -req->a_res.lock.fl.fl_pid;
+			break;
+		default:
+			status = nlm_stat_to_errno(req->a_res.status);
+	}
+out:
+	trace_nlmclnt_test(&req->a_args.lock,
+			   (const struct sockaddr *)&req->a_host->h_addr,
+			   req->a_host->h_addrlen, req->a_res.status);
+	nlmclnt_release_call(req);
+	return status;
+}
+
+static void nlmclnt_locks_copy_lock(struct file_lock *new, struct file_lock *fl)
+{
+	spin_lock(&fl->fl_u.nfs_fl.owner->host->h_lock);
+	new->fl_u.nfs_fl.state = fl->fl_u.nfs_fl.state;
+	new->fl_u.nfs_fl.owner = nlmclnt_get_lockowner(fl->fl_u.nfs_fl.owner);
+	list_add_tail(&new->fl_u.nfs_fl.list, &fl->fl_u.nfs_fl.owner->host->h_granted);
+	spin_unlock(&fl->fl_u.nfs_fl.owner->host->h_lock);
+}
+
+static void nlmclnt_locks_release_private(struct file_lock *fl)
+{
+	spin_lock(&fl->fl_u.nfs_fl.owner->host->h_lock);
+	list_del(&fl->fl_u.nfs_fl.list);
+	spin_unlock(&fl->fl_u.nfs_fl.owner->host->h_lock);
+	nlmclnt_put_lockowner(fl->fl_u.nfs_fl.owner);
+}
+
+static const struct file_lock_operations nlmclnt_lock_ops = {
+	.fl_copy_lock = nlmclnt_locks_copy_lock,
+	.fl_release_private = nlmclnt_locks_release_private,
+};
+
+static void nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host)
+{
+	fl->fl_u.nfs_fl.state = 0;
+	fl->fl_u.nfs_fl.owner = nlmclnt_find_lockowner(host, fl->fl_owner);
+	INIT_LIST_HEAD(&fl->fl_u.nfs_fl.list);
+	fl->fl_ops = &nlmclnt_lock_ops;
+}
+
+static int do_vfs_lock(struct file_lock *fl)
+{
+	return locks_lock_file_wait(fl->fl_file, fl);
+}
+
+/*
+ * LOCK: Try to create a lock
+ *
+ *			Programmer Harassment Alert
+ *
+ * When given a blocking lock request in a sync RPC call, the HPUX lockd
+ * will faithfully return LCK_BLOCKED but never cares to notify us when
+ * the lock could be granted. This way, our local process could hang
+ * around forever waiting for the callback.
+ *
+ *  Solution A:	Implement busy-waiting
+ *  Solution B: Use the async version of the call (NLM_LOCK_{MSG,RES})
+ *
+ * For now I am implementing solution A, because I hate the idea of
+ * re-implementing lockd for a third time in two months. The async
+ * calls shouldn't be too hard to do, however.
+ *
+ * This is one of the lovely things about standards in the NFS area:
+ * they're so soft and squishy you can't really blame HP for doing this.
+ */
+static int
+nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
+{
+	const struct cred *cred = nfs_file_cred(fl->fl_file);
+	struct nlm_host	*host = req->a_host;
+	struct nlm_res	*resp = &req->a_res;
+	struct nlm_wait block;
+	unsigned char fl_flags = fl->fl_flags;
+	unsigned char fl_type;
+	__be32 b_status;
+	int status = -ENOLCK;
+
+	if (nsm_monitor(host) < 0)
+		goto out;
+	req->a_args.state = nsm_local_state;
+
+	fl->fl_flags |= FL_ACCESS;
+	status = do_vfs_lock(fl);
+	fl->fl_flags = fl_flags;
+	if (status < 0)
+		goto out;
+
+	nlmclnt_prepare_block(&block, host, fl);
+again:
+	/*
+	 * Initialise resp->status to a valid non-zero value,
+	 * since 0 == nlm_lck_granted
+	 */
+	resp->status = nlm_lck_blocked;
+
+	/*
+	 * A GRANTED callback can come at any time -- even before the reply
+	 * to the LOCK request arrives, so we queue the wait before
+	 * requesting the lock.
+	 */
+	nlmclnt_queue_block(&block);
+	for (;;) {
+		/* Reboot protection */
+		fl->fl_u.nfs_fl.state = host->h_state;
+		status = nlmclnt_call(cred, req, NLMPROC_LOCK);
+		if (status < 0)
+			break;
+		/* Did a reclaimer thread notify us of a server reboot? */
+		if (resp->status == nlm_lck_denied_grace_period)
+			continue;
+		if (resp->status != nlm_lck_blocked)
+			break;
+		/* Wait on an NLM blocking lock */
+		status = nlmclnt_wait(&block, req, NLMCLNT_POLL_TIMEOUT);
+		if (status < 0)
+			break;
+		if (block.b_status != nlm_lck_blocked)
+			break;
+	}
+	b_status = nlmclnt_dequeue_block(&block);
+	if (resp->status == nlm_lck_blocked)
+		resp->status = b_status;
+
+	/* if we were interrupted while blocking, then cancel the lock request
+	 * and exit
+	 */
+	if (resp->status == nlm_lck_blocked) {
+		if (!req->a_args.block)
+			goto out_unlock;
+		if (nlmclnt_cancel(host, req->a_args.block, fl) == 0)
+			goto out;
+	}
+
+	if (resp->status == nlm_granted) {
+		down_read(&host->h_rwsem);
+		/* Check whether or not the server has rebooted */
+		if (fl->fl_u.nfs_fl.state != host->h_state) {
+			up_read(&host->h_rwsem);
+			goto again;
+		}
+		/* Ensure the resulting lock will get added to granted list */
+		fl->fl_flags |= FL_SLEEP;
+		if (do_vfs_lock(fl) < 0)
+			printk(KERN_WARNING "%s: VFS is out of sync with lock manager!\n", __func__);
+		up_read(&host->h_rwsem);
+		fl->fl_flags = fl_flags;
+		status = 0;
+	}
+	if (status < 0)
+		goto out_unlock;
+	/*
+	 * EAGAIN doesn't make sense for sleeping locks, and in some
+	 * cases NLM_LCK_DENIED is returned for a permanent error.  So
+	 * turn it into an ENOLCK.
+	 */
+	if (resp->status == nlm_lck_denied && (fl_flags & FL_SLEEP))
+		status = -ENOLCK;
+	else
+		status = nlm_stat_to_errno(resp->status);
+out:
+	trace_nlmclnt_lock(&req->a_args.lock,
+			   (const struct sockaddr *)&req->a_host->h_addr,
+			   req->a_host->h_addrlen, req->a_res.status);
+	nlmclnt_release_call(req);
+	return status;
+out_unlock:
+	/* Fatal error: ensure that we remove the lock altogether */
+	trace_nlmclnt_lock(&req->a_args.lock,
+			   (const struct sockaddr *)&req->a_host->h_addr,
+			   req->a_host->h_addrlen, req->a_res.status);
+	dprintk("lockd: lock attempt ended in fatal error.\n"
+		"       Attempting to unlock.\n");
+	fl_type = fl->fl_type;
+	fl->fl_type = F_UNLCK;
+	down_read(&host->h_rwsem);
+	do_vfs_lock(fl);
+	up_read(&host->h_rwsem);
+	fl->fl_type = fl_type;
+	fl->fl_flags = fl_flags;
+	nlmclnt_async_call(cred, req, NLMPROC_UNLOCK, &nlmclnt_unlock_ops);
+	return status;
+}
+
+/*
+ * RECLAIM: Try to reclaim a lock
+ */
+int
+nlmclnt_reclaim(struct nlm_host *host, struct file_lock *fl,
+		struct nlm_rqst *req)
+{
+	int		status;
+
+	memset(req, 0, sizeof(*req));
+	locks_init_lock(&req->a_args.lock.fl);
+	locks_init_lock(&req->a_res.lock.fl);
+	req->a_host  = host;
+
+	/* Set up the argument struct */
+	nlmclnt_setlockargs(req, fl);
+	req->a_args.reclaim = 1;
+
+	status = nlmclnt_call(nfs_file_cred(fl->fl_file), req, NLMPROC_LOCK);
+	if (status >= 0 && req->a_res.status == nlm_granted)
+		return 0;
+
+	printk(KERN_WARNING "lockd: failed to reclaim lock for pid %d "
+				"(errno %d, status %d)\n", fl->fl_pid,
+				status, ntohl(req->a_res.status));
+
+	/*
+	 * FIXME: This is a serious failure. We can
+	 *
+	 *  a.	Ignore the problem
+	 *  b.	Send the owning process some signal (Linux doesn't have
+	 *	SIGLOST, though...)
+	 *  c.	Retry the operation
+	 *
+	 * Until someone comes up with a simple implementation
+	 * for b or c, I'll choose option a.
+	 */
+
+	return -ENOLCK;
+}
+
+/*
+ * UNLOCK: remove an existing lock
+ */
+static int
+nlmclnt_unlock(struct nlm_rqst *req, struct file_lock *fl)
+{
+	struct nlm_host	*host = req->a_host;
+	struct nlm_res	*resp = &req->a_res;
+	int status;
+	unsigned char fl_flags = fl->fl_flags;
+
+	/*
+	 * Note: the server is supposed to either grant us the unlock
+	 * request, or to deny it with NLM_LCK_DENIED_GRACE_PERIOD. In either
+	 * case, we want to unlock.
+	 */
+	fl->fl_flags |= FL_EXISTS;
+	down_read(&host->h_rwsem);
+	status = do_vfs_lock(fl);
+	up_read(&host->h_rwsem);
+	fl->fl_flags = fl_flags;
+	if (status == -ENOENT) {
+		status = 0;
+		goto out;
+	}
+
+	refcount_inc(&req->a_count);
+	status = nlmclnt_async_call(nfs_file_cred(fl->fl_file), req,
+			NLMPROC_UNLOCK, &nlmclnt_unlock_ops);
+	if (status < 0)
+		goto out;
+
+	if (resp->status == nlm_granted)
+		goto out;
+
+	if (resp->status != nlm_lck_denied_nolocks)
+		printk("lockd: unexpected unlock status: %d\n",
+			ntohl(resp->status));
+	/* What to do now? I'm out of my depth... */
+	status = -ENOLCK;
+out:
+	trace_nlmclnt_unlock(&req->a_args.lock,
+			     (const struct sockaddr *)&req->a_host->h_addr,
+			     req->a_host->h_addrlen, req->a_res.status);
+	nlmclnt_release_call(req);
+	return status;
+}
+
+static void nlmclnt_unlock_prepare(struct rpc_task *task, void *data)
+{
+	struct nlm_rqst	*req = data;
+	const struct nlmclnt_operations *nlmclnt_ops = req->a_host->h_nlmclnt_ops;
+	bool defer_call = false;
+
+	if (nlmclnt_ops && nlmclnt_ops->nlmclnt_unlock_prepare)
+		defer_call = nlmclnt_ops->nlmclnt_unlock_prepare(task, req->a_callback_data);
+
+	if (!defer_call)
+		rpc_call_start(task);
+}
+
+static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)
+{
+	struct nlm_rqst	*req = data;
+	u32 status = ntohl(req->a_res.status);
+
+	if (RPC_SIGNALLED(task))
+		goto die;
+
+	if (task->tk_status < 0) {
+		dprintk("lockd: unlock failed (err = %d)\n", -task->tk_status);
+		switch (task->tk_status) {
+		case -EACCES:
+		case -EIO:
+			goto die;
+		default:
+			goto retry_rebind;
+		}
+	}
+	if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
+		rpc_delay(task, NLMCLNT_GRACE_WAIT);
+		goto retry_unlock;
+	}
+	if (status != NLM_LCK_GRANTED)
+		printk(KERN_WARNING "lockd: unexpected unlock status: %d\n", status);
+die:
+	return;
+ retry_rebind:
+	nlm_rebind_host(req->a_host);
+ retry_unlock:
+	rpc_restart_call(task);
+}
+
+static const struct rpc_call_ops nlmclnt_unlock_ops = {
+	.rpc_call_prepare = nlmclnt_unlock_prepare,
+	.rpc_call_done = nlmclnt_unlock_callback,
+	.rpc_release = nlmclnt_rpc_release,
+};
+
+/*
+ * Cancel a blocked lock request.
+ * We always use an async RPC call for this in order not to hang a
+ * process that has been Ctrl-C'ed.
+ */
+static int nlmclnt_cancel(struct nlm_host *host, int block, struct file_lock *fl)
+{
+	struct nlm_rqst	*req;
+	int status;
+
+	dprintk("lockd: blocking lock attempt was interrupted by a signal.\n"
+		"       Attempting to cancel lock.\n");
+
+	req = nlm_alloc_call(host);
+	if (!req)
+		return -ENOMEM;
+	req->a_flags = RPC_TASK_ASYNC;
+
+	nlmclnt_setlockargs(req, fl);
+	req->a_args.block = block;
+
+	refcount_inc(&req->a_count);
+	status = nlmclnt_async_call(nfs_file_cred(fl->fl_file), req,
+			NLMPROC_CANCEL, &nlmclnt_cancel_ops);
+	if (status == 0 && req->a_res.status == nlm_lck_denied)
+		status = -ENOLCK;
+	nlmclnt_release_call(req);
+	return status;
+}
+
+static void nlmclnt_cancel_callback(struct rpc_task *task, void *data)
+{
+	struct nlm_rqst	*req = data;
+	u32 status = ntohl(req->a_res.status);
+
+	if (RPC_SIGNALLED(task))
+		goto die;
+
+	if (task->tk_status < 0) {
+		dprintk("lockd: CANCEL call error %d, retrying.\n",
+					task->tk_status);
+		goto retry_cancel;
+	}
+
+	switch (status) {
+	case NLM_LCK_GRANTED:
+	case NLM_LCK_DENIED_GRACE_PERIOD:
+	case NLM_LCK_DENIED:
+		/* Everything's good */
+		break;
+	case NLM_LCK_DENIED_NOLOCKS:
+		dprintk("lockd: CANCEL failed (server has no locks)\n");
+		goto retry_cancel;
+	default:
+		printk(KERN_NOTICE "lockd: weird return %d for CANCEL call\n",
+			status);
+	}
+
+die:
+	return;
+
+retry_cancel:
+	/* Don't ever retry more than 3 times */
+	if (req->a_retries++ >= NLMCLNT_MAX_RETRIES)
+		goto die;
+	nlm_rebind_host(req->a_host);
+	rpc_restart_call(task);
+	rpc_delay(task, 30 * HZ);
+}
+
+static const struct rpc_call_ops nlmclnt_cancel_ops = {
+	.rpc_call_done = nlmclnt_cancel_callback,
+	.rpc_release = nlmclnt_rpc_release,
+};
+
+/*
+ * Convert an NLM status code to a generic kernel errno
+ */
+static int
+nlm_stat_to_errno(__be32 status)
+{
+	switch(ntohl(status)) {
+	case NLM_LCK_GRANTED:
+		return 0;
+	case NLM_LCK_DENIED:
+		return -EAGAIN;
+	case NLM_LCK_DENIED_NOLOCKS:
+	case NLM_LCK_DENIED_GRACE_PERIOD:
+		return -ENOLCK;
+	case NLM_LCK_BLOCKED:
+		printk(KERN_NOTICE "lockd: unexpected status NLM_BLOCKED\n");
+		return -ENOLCK;
+#ifdef CONFIG_LOCKD_V4
+	case NLM_DEADLCK:
+		return -EDEADLK;
+	case NLM_ROFS:
+		return -EROFS;
+	case NLM_STALE_FH:
+		return -ESTALE;
+	case NLM_FBIG:
+		return -EOVERFLOW;
+	case NLM_FAILED:
+		return -ENOLCK;
+#endif
+	}
+	printk(KERN_NOTICE "lockd: unexpected server status %d\n",
+		 ntohl(status));
+	return -ENOLCK;
+}