fs/dlm/plock.c - LeafOS-Devices/android_kernel_samsung_exynos9820 - Gitiles

 /*
  * Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
  *
  * This copyrighted material is made available to anyone wishing to use,
  * modify, copy, or redistribute it subject to the terms and conditions
  * of the GNU General Public License version 2.
  */

 #include <linux/fs.h>
 #include <linux/miscdevice.h>
 #include <linux/poll.h>
 #include <linux/dlm.h>
 #include <linux/dlm_plock.h>
 #include <linux/slab.h>

 #include "dlm_internal.h"
 #include "lockspace.h"

 static spinlock_t ops_lock;
 static struct list_head send_list;
 static struct list_head recv_list;
 static wait_queue_head_t send_wq;
 static wait_queue_head_t recv_wq;

 struct plock_async_data {
 	void *fl;
 	void *file;
 	struct file_lock flc;
 	int (*callback)(struct file_lock *fl, int result);
 };

 struct plock_op {
 	struct list_head list;
 	int done;
 	struct dlm_plock_info info;
 	/* if set indicates async handling */
 	struct plock_async_data *data;
 };

 static inline void set_version(struct dlm_plock_info *info)
 {
 	info->version[0] = DLM_PLOCK_VERSION_MAJOR;
 	info->version[1] = DLM_PLOCK_VERSION_MINOR;
 	info->version[2] = DLM_PLOCK_VERSION_PATCH;
 }

 static int check_version(struct dlm_plock_info *info)
 {
 	if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
 	    (DLM_PLOCK_VERSION_MINOR < info->version[1])) {
 		log_print("plock device version mismatch: "
 			  "kernel (%u.%u.%u), user (%u.%u.%u)",
 			  DLM_PLOCK_VERSION_MAJOR,
 			  DLM_PLOCK_VERSION_MINOR,
 			  DLM_PLOCK_VERSION_PATCH,
 			  info->version[0],
 			  info->version[1],
 			  info->version[2]);
 		return -EINVAL;
 	}
 	return 0;
 }

 static void dlm_release_plock_op(struct plock_op *op)
 {
 	kfree(op->data);
 	kfree(op);
 }

 static void send_op(struct plock_op *op)
 {
 	set_version(&op->info);
 	INIT_LIST_HEAD(&op->list);
 	spin_lock(&ops_lock);
 	list_add_tail(&op->list, &send_list);
 	spin_unlock(&ops_lock);
 	wake_up(&send_wq);
 }

 /* If a process was killed while waiting for the only plock on a file,
    locks_remove_posix will not see any lock on the file so it won't
    send an unlock-close to us to pass on to userspace to clean up the
    abandoned waiter.  So, we have to insert the unlock-close when the
    lock call is interrupted. */

 static void do_unlock_close(const struct dlm_plock_info *info)
 {
 	struct plock_op *op;

 	op = kzalloc(sizeof(*op), GFP_NOFS);
 	if (!op)
 		return;

 	op->info.optype		= DLM_PLOCK_OP_UNLOCK;
 	op->info.pid		= info->pid;
 	op->info.fsid		= info->fsid;
 	op->info.number		= info->number;
 	op->info.start		= 0;
 	op->info.end		= OFFSET_MAX;
 	op->info.owner		= info->owner;

 	op->info.flags |= DLM_PLOCK_FL_CLOSE;
 	send_op(op);
 }

 int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 		   int cmd, struct file_lock *fl)
 {
 	struct plock_async_data *op_data;
 	struct dlm_ls *ls;
 	struct plock_op *op;
 	int rv;

 	ls = dlm_find_lockspace_local(lockspace);
 	if (!ls)
 		return -EINVAL;

 	op = kzalloc(sizeof(*op), GFP_NOFS);
 	if (!op) {
 		rv = -ENOMEM;
 		goto out;
 	}

 	op->info.optype		= DLM_PLOCK_OP_LOCK;
 	op->info.pid		= fl->fl_pid;
 	op->info.ex		= (fl->fl_type == F_WRLCK);
 	op->info.wait		= IS_SETLKW(cmd);
 	op->info.fsid		= ls->ls_global_id;
 	op->info.number		= number;
 	op->info.start		= fl->fl_start;
 	op->info.end		= fl->fl_end;
 	/* async handling */
 	if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
 		op_data = kzalloc(sizeof(*op_data), GFP_NOFS);
 		if (!op_data) {
 			dlm_release_plock_op(op);
 			rv = -ENOMEM;
 			goto out;
 		}

 		/* fl_owner is lockd which doesn't distinguish
 		   processes on the nfs client */
 		op->info.owner	= (__u64) fl->fl_pid;
 		op_data->callback = fl->fl_lmops->lm_grant;
 		locks_init_lock(&op_data->flc);
 		locks_copy_lock(&op_data->flc, fl);
 		op_data->fl		= fl;
 		op_data->file	= file;

 		op->data = op_data;

 		send_op(op);
 		rv = FILE_LOCK_DEFERRED;
 		goto out;
 	} else {
 		op->info.owner	= (__u64)(long) fl->fl_owner;
 	}

 	send_op(op);

 	rv = wait_event_killable(recv_wq, (op->done != 0));
 	if (rv == -ERESTARTSYS) {
 		spin_lock(&ops_lock);
 		list_del(&op->list);
 		spin_unlock(&ops_lock);
 		log_debug(ls, "%s: wait interrupted %x %llx pid %d",
 			  __func__, ls->ls_global_id,
 			  (unsigned long long)number, op->info.pid);
 		dlm_release_plock_op(op);
 		do_unlock_close(&op->info);
 		goto out;
 	}

 	spin_lock(&ops_lock);
 	if (!list_empty(&op->list)) {
 		log_error(ls, "dlm_posix_lock: op on list %llx",
 			  (unsigned long long)number);
 		list_del(&op->list);
 	}
 	spin_unlock(&ops_lock);

 	rv = op->info.rv;

 	if (!rv) {
 		if (locks_lock_file_wait(file, fl) < 0)
 			log_error(ls, "dlm_posix_lock: vfs lock error %llx",
 				  (unsigned long long)number);
 	}

 	dlm_release_plock_op(op);
 out:
 	dlm_put_lockspace(ls);
 	return rv;
 }
 EXPORT_SYMBOL_GPL(dlm_posix_lock);

 /* Returns failure iff a successful lock operation should be canceled */
 static int dlm_plock_callback(struct plock_op *op)
 {
 	struct plock_async_data *op_data = op->data;
 	struct file *file;
 	struct file_lock *fl;
 	struct file_lock *flc;
 	int (*notify)(struct file_lock *fl, int result) = NULL;
 	int rv = 0;

 	spin_lock(&ops_lock);
 	if (!list_empty(&op->list)) {
 		log_print("dlm_plock_callback: op on list %llx",
 			  (unsigned long long)op->info.number);
 		list_del(&op->list);
 	}
 	spin_unlock(&ops_lock);

 	/* check if the following 2 are still valid or make a copy */
 	file = op_data->file;
 	flc = &op_data->flc;
 	fl = op_data->fl;
 	notify = op_data->callback;

 	if (op->info.rv) {
 		notify(fl, op->info.rv);
 		goto out;
 	}

 	/* got fs lock; bookkeep locally as well: */
 	flc->fl_flags &= ~FL_SLEEP;
 	if (posix_lock_file(file, flc, NULL)) {
 		/*
 		 * This can only happen in the case of kmalloc() failure.
 		 * The filesystem's own lock is the authoritative lock,
 		 * so a failure to get the lock locally is not a disaster.
 		 * As long as the fs cannot reliably cancel locks (especially
 		 * in a low-memory situation), we're better off ignoring
 		 * this failure than trying to recover.
 		 */
 		log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
 			  (unsigned long long)op->info.number, file, fl);
 	}

 	rv = notify(fl, 0);
 	if (rv) {
 		/* XXX: We need to cancel the fs lock here: */
 		log_print("dlm_plock_callback: lock granted after lock request "
 			  "failed; dangling lock!\n");
 		goto out;
 	}

 out:
 	dlm_release_plock_op(op);
 	return rv;
 }

 int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 		     struct file_lock *fl)
 {
 	struct dlm_ls *ls;
 	struct plock_op *op;
 	int rv;
 	unsigned char fl_flags = fl->fl_flags;

 	ls = dlm_find_lockspace_local(lockspace);
 	if (!ls)
 		return -EINVAL;

 	op = kzalloc(sizeof(*op), GFP_NOFS);
 	if (!op) {
 		rv = -ENOMEM;
 		goto out;
 	}

 	/* cause the vfs unlock to return ENOENT if lock is not found */
 	fl->fl_flags |= FL_EXISTS;

 	rv = locks_lock_file_wait(file, fl);
 	if (rv == -ENOENT) {
 		rv = 0;
 		goto out_free;
 	}
 	if (rv < 0) {
 		log_error(ls, "dlm_posix_unlock: vfs unlock error %d %llx",
 			  rv, (unsigned long long)number);
 	}

 	op->info.optype		= DLM_PLOCK_OP_UNLOCK;
 	op->info.pid		= fl->fl_pid;
 	op->info.fsid		= ls->ls_global_id;
 	op->info.number		= number;
 	op->info.start		= fl->fl_start;
 	op->info.end		= fl->fl_end;
 	if (fl->fl_lmops && fl->fl_lmops->lm_grant)
 		op->info.owner	= (__u64) fl->fl_pid;
 	else
 		op->info.owner	= (__u64)(long) fl->fl_owner;

 	if (fl->fl_flags & FL_CLOSE) {
 		op->info.flags |= DLM_PLOCK_FL_CLOSE;
 		send_op(op);
 		rv = 0;
 		goto out;
 	}

 	send_op(op);
 	wait_event(recv_wq, (op->done != 0));

 	spin_lock(&ops_lock);
 	if (!list_empty(&op->list)) {
 		log_error(ls, "dlm_posix_unlock: op on list %llx",
 			  (unsigned long long)number);
 		list_del(&op->list);
 	}
 	spin_unlock(&ops_lock);

 	rv = op->info.rv;

 	if (rv == -ENOENT)
 		rv = 0;

 out_free:
 	dlm_release_plock_op(op);
 out:
 	dlm_put_lockspace(ls);
 	fl->fl_flags = fl_flags;
 	return rv;
 }
 EXPORT_SYMBOL_GPL(dlm_posix_unlock);

 int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 		  struct file_lock *fl)
 {
 	struct dlm_ls *ls;
 	struct plock_op *op;
 	int rv;

 	ls = dlm_find_lockspace_local(lockspace);
 	if (!ls)
 		return -EINVAL;

 	op = kzalloc(sizeof(*op), GFP_NOFS);
 	if (!op) {
 		rv = -ENOMEM;
 		goto out;
 	}

 	op->info.optype		= DLM_PLOCK_OP_GET;
 	op->info.pid		= fl->fl_pid;
 	op->info.ex		= (fl->fl_type == F_WRLCK);
 	op->info.fsid		= ls->ls_global_id;
 	op->info.number		= number;
 	op->info.start		= fl->fl_start;
 	op->info.end		= fl->fl_end;
 	if (fl->fl_lmops && fl->fl_lmops->lm_grant)
 		op->info.owner	= (__u64) fl->fl_pid;
 	else
 		op->info.owner	= (__u64)(long) fl->fl_owner;

 	send_op(op);
 	wait_event(recv_wq, (op->done != 0));

 	spin_lock(&ops_lock);
 	if (!list_empty(&op->list)) {
 		log_error(ls, "dlm_posix_get: op on list %llx",
 			  (unsigned long long)number);
 		list_del(&op->list);
 	}
 	spin_unlock(&ops_lock);

 	/* info.rv from userspace is 1 for conflict, 0 for no-conflict,
 	   -ENOENT if there are no locks on the file */

 	rv = op->info.rv;

 	fl->fl_type = F_UNLCK;
 	if (rv == -ENOENT)
 		rv = 0;
 	else if (rv > 0) {
 		locks_init_lock(fl);
 		fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
 		fl->fl_flags = FL_POSIX;
 		fl->fl_pid = op->info.pid;
 		if (op->info.nodeid != dlm_our_nodeid())
 			fl->fl_pid = -fl->fl_pid;
 		fl->fl_start = op->info.start;
 		fl->fl_end = op->info.end;
 		rv = 0;
 	}

 	dlm_release_plock_op(op);
 out:
 	dlm_put_lockspace(ls);
 	return rv;
 }
 EXPORT_SYMBOL_GPL(dlm_posix_get);

 /* a read copies out one plock request from the send list */
 static ssize_t dev_read(struct file *file, char __user *u, size_t count,
 			loff_t *ppos)
 {
 	struct dlm_plock_info info;
 	struct plock_op *op = NULL;

 	if (count < sizeof(info))
 		return -EINVAL;

 	spin_lock(&ops_lock);
 	if (!list_empty(&send_list)) {
 		op = list_entry(send_list.next, struct plock_op, list);
 		if (op->info.flags & DLM_PLOCK_FL_CLOSE)
 			list_del(&op->list);
 		else
 			list_move_tail(&op->list, &recv_list);
 		memcpy(&info, &op->info, sizeof(info));
 	}
 	spin_unlock(&ops_lock);

 	if (!op)
 		return -EAGAIN;

 	/* there is no need to get a reply from userspace for unlocks
 	   that were generated by the vfs cleaning up for a close
 	   (the process did not make an unlock call). */

 	if (op->info.flags & DLM_PLOCK_FL_CLOSE)
 		dlm_release_plock_op(op);

 	if (copy_to_user(u, &info, sizeof(info)))
 		return -EFAULT;
 	return sizeof(info);
 }

 /* a write copies in one plock result that should match a plock_op
    on the recv list */
 static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
 			 loff_t *ppos)
 {
 	struct plock_op *op = NULL, *iter;
 	struct dlm_plock_info info;
 	int do_callback = 0;

 	if (count != sizeof(info))
 		return -EINVAL;

 	if (copy_from_user(&info, u, sizeof(info)))
 		return -EFAULT;

 	if (check_version(&info))
 		return -EINVAL;

 	/*
 	 * The results for waiting ops (SETLKW) can be returned in any
 	 * order, so match all fields to find the op.  The results for
 	 * non-waiting ops are returned in the order that they were sent
 	 * to userspace, so match the result with the first non-waiting op.
 	 */
 	spin_lock(&ops_lock);
 	if (info.wait) {
 		list_for_each_entry(iter, &recv_list, list) {
 			if (iter->info.fsid == info.fsid &&
 			    iter->info.number == info.number &&
 			    iter->info.owner == info.owner &&
 			    iter->info.pid == info.pid &&
 			    iter->info.start == info.start &&
 			    iter->info.end == info.end &&
 			    iter->info.ex == info.ex &&
 			    iter->info.wait) {
 				op = iter;
 				break;
 			}
 		}
 	} else {
 		list_for_each_entry(iter, &recv_list, list) {
 			if (!iter->info.wait &&
 			    iter->info.fsid == info.fsid) {
 				op = iter;
 				break;
 			}
 		}
 	}

 	if (op) {
 		/* Sanity check that op and info match. */
 		if (info.wait)
 			WARN_ON(op->info.optype != DLM_PLOCK_OP_LOCK);
 		else
 			WARN_ON(op->info.number != info.number ||
 				op->info.owner != info.owner ||
 				op->info.optype != info.optype);

 		list_del_init(&op->list);
 		memcpy(&op->info, &info, sizeof(info));
 		if (op->data)
 			do_callback = 1;
 		else
 			op->done = 1;
 	}
 	spin_unlock(&ops_lock);

 	if (op) {
 		if (do_callback)
 			dlm_plock_callback(op);
 		else
 			wake_up(&recv_wq);
 	} else
 		log_print("%s: no op %x %llx", __func__,
 			  info.fsid, (unsigned long long)info.number);
 	return count;
 }

 static unsigned int dev_poll(struct file *file, poll_table *wait)
 {
 	unsigned int mask = 0;

 	poll_wait(file, &send_wq, wait);

 	spin_lock(&ops_lock);
 	if (!list_empty(&send_list))
 		mask = POLLIN | POLLRDNORM;
 	spin_unlock(&ops_lock);

 	return mask;
 }

 static const struct file_operations dev_fops = {
 	.read    = dev_read,
 	.write   = dev_write,
 	.poll    = dev_poll,
 	.owner   = THIS_MODULE,
 	.llseek  = noop_llseek,
 };

 static struct miscdevice plock_dev_misc = {
 	.minor = MISC_DYNAMIC_MINOR,
 	.name = DLM_PLOCK_MISC_NAME,
 	.fops = &dev_fops
 };

 int dlm_plock_init(void)
 {
 	int rv;

 	spin_lock_init(&ops_lock);
 	INIT_LIST_HEAD(&send_list);
 	INIT_LIST_HEAD(&recv_list);
 	init_waitqueue_head(&send_wq);
 	init_waitqueue_head(&recv_wq);

 	rv = misc_register(&plock_dev_misc);
 	if (rv)
 		log_print("dlm_plock_init: misc_register failed %d", rv);
 	return rv;
 }

 void dlm_plock_exit(void)
 {
 	misc_deregister(&plock_dev_misc);
 }
	/*
	* Copyright (C) 2005-2008 Red Hat, Inc. All rights reserved.
	*
	* This copyrighted material is made available to anyone wishing to use,
	* modify, copy, or redistribute it subject to the terms and conditions
	* of the GNU General Public License version 2.
	*/

	#include <linux/fs.h>
	#include <linux/miscdevice.h>
	#include <linux/poll.h>
	#include <linux/dlm.h>
	#include <linux/dlm_plock.h>
	#include <linux/slab.h>

	#include "dlm_internal.h"
	#include "lockspace.h"

	static spinlock_t ops_lock;
	static struct list_head send_list;
	static struct list_head recv_list;
	static wait_queue_head_t send_wq;
	static wait_queue_head_t recv_wq;

	struct plock_async_data {
	void *fl;
	void *file;
	struct file_lock flc;
	int (callback)(struct file_lock fl, int result);
	};

	struct plock_op {
	struct list_head list;
	int done;
	struct dlm_plock_info info;
	/* if set indicates async handling */
	struct plock_async_data *data;
	};

	static inline void set_version(struct dlm_plock_info *info)
	{
	info->version[0] = DLM_PLOCK_VERSION_MAJOR;
	info->version[1] = DLM_PLOCK_VERSION_MINOR;
	info->version[2] = DLM_PLOCK_VERSION_PATCH;
	}

	static int check_version(struct dlm_plock_info *info)
	{
	if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) \|\|
	(DLM_PLOCK_VERSION_MINOR < info->version[1])) {
	log_print("plock device version mismatch: "
	"kernel (%u.%u.%u), user (%u.%u.%u)",
	DLM_PLOCK_VERSION_MAJOR,
	DLM_PLOCK_VERSION_MINOR,
	DLM_PLOCK_VERSION_PATCH,
	info->version[0],
	info->version[1],
	info->version[2]);
	return -EINVAL;
	}
	return 0;
	}

	static void dlm_release_plock_op(struct plock_op *op)
	{
	kfree(op->data);
	kfree(op);
	}

	static void send_op(struct plock_op *op)
	{
	set_version(&op->info);
	INIT_LIST_HEAD(&op->list);
	spin_lock(&ops_lock);
	list_add_tail(&op->list, &send_list);
	spin_unlock(&ops_lock);
	wake_up(&send_wq);
	}

	/* If a process was killed while waiting for the only plock on a file,
	locks_remove_posix will not see any lock on the file so it won't
	send an unlock-close to us to pass on to userspace to clean up the
	abandoned waiter. So, we have to insert the unlock-close when the
	lock call is interrupted. */

	static void do_unlock_close(const struct dlm_plock_info *info)
	{
	struct plock_op *op;

	op = kzalloc(sizeof(*op), GFP_NOFS);
	if (!op)
	return;

	op->info.optype = DLM_PLOCK_OP_UNLOCK;
	op->info.pid = info->pid;
	op->info.fsid = info->fsid;
	op->info.number = info->number;
	op->info.start = 0;
	op->info.end = OFFSET_MAX;
	op->info.owner = info->owner;

	op->info.flags \|= DLM_PLOCK_FL_CLOSE;
	send_op(op);
	}

	int dlm_posix_lock(dlm_lockspace_t lockspace, u64 number, struct file file,
	int cmd, struct file_lock *fl)
	{
	struct plock_async_data *op_data;
	struct dlm_ls *ls;
	struct plock_op *op;
	int rv;

	ls = dlm_find_lockspace_local(lockspace);
	if (!ls)
	return -EINVAL;

	op = kzalloc(sizeof(*op), GFP_NOFS);
	if (!op) {
	rv = -ENOMEM;
	goto out;
	}

	op->info.optype = DLM_PLOCK_OP_LOCK;
	op->info.pid = fl->fl_pid;
	op->info.ex = (fl->fl_type == F_WRLCK);
	op->info.wait = IS_SETLKW(cmd);
	op->info.fsid = ls->ls_global_id;
	op->info.number = number;
	op->info.start = fl->fl_start;
	op->info.end = fl->fl_end;
	/* async handling */
	if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
	op_data = kzalloc(sizeof(*op_data), GFP_NOFS);
	if (!op_data) {
	dlm_release_plock_op(op);
	rv = -ENOMEM;
	goto out;
	}

	/* fl_owner is lockd which doesn't distinguish
	processes on the nfs client */
	op->info.owner = (__u64) fl->fl_pid;
	op_data->callback = fl->fl_lmops->lm_grant;
	locks_init_lock(&op_data->flc);
	locks_copy_lock(&op_data->flc, fl);
	op_data->fl = fl;
	op_data->file = file;

	op->data = op_data;

	send_op(op);
	rv = FILE_LOCK_DEFERRED;
	goto out;
	} else {
	op->info.owner = (__u64)(long) fl->fl_owner;
	}

	send_op(op);

	rv = wait_event_killable(recv_wq, (op->done != 0));
	if (rv == -ERESTARTSYS) {
	spin_lock(&ops_lock);
	list_del(&op->list);
	spin_unlock(&ops_lock);
	log_debug(ls, "%s: wait interrupted %x %llx pid %d",
	__func__, ls->ls_global_id,
	(unsigned long long)number, op->info.pid);
	dlm_release_plock_op(op);
	do_unlock_close(&op->info);
	goto out;
	}

	spin_lock(&ops_lock);
	if (!list_empty(&op->list)) {
	log_error(ls, "dlm_posix_lock: op on list %llx",
	(unsigned long long)number);
	list_del(&op->list);
	}
	spin_unlock(&ops_lock);

	rv = op->info.rv;

	if (!rv) {
	if (locks_lock_file_wait(file, fl) < 0)
	log_error(ls, "dlm_posix_lock: vfs lock error %llx",
	(unsigned long long)number);
	}

	dlm_release_plock_op(op);
	out:
	dlm_put_lockspace(ls);
	return rv;
	}
	EXPORT_SYMBOL_GPL(dlm_posix_lock);

	/* Returns failure iff a successful lock operation should be canceled */
	static int dlm_plock_callback(struct plock_op *op)
	{
	struct plock_async_data *op_data = op->data;
	struct file *file;
	struct file_lock *fl;
	struct file_lock *flc;
	int (notify)(struct file_lock fl, int result) = NULL;
	int rv = 0;

	spin_lock(&ops_lock);
	if (!list_empty(&op->list)) {
	log_print("dlm_plock_callback: op on list %llx",
	(unsigned long long)op->info.number);
	list_del(&op->list);
	}
	spin_unlock(&ops_lock);

	/* check if the following 2 are still valid or make a copy */
	file = op_data->file;
	flc = &op_data->flc;
	fl = op_data->fl;
	notify = op_data->callback;

	if (op->info.rv) {
	notify(fl, op->info.rv);
	goto out;
	}

	/* got fs lock; bookkeep locally as well: */
	flc->fl_flags &= ~FL_SLEEP;
	if (posix_lock_file(file, flc, NULL)) {
	/*
	* This can only happen in the case of kmalloc() failure.
	* The filesystem's own lock is the authoritative lock,
	* so a failure to get the lock locally is not a disaster.
	* As long as the fs cannot reliably cancel locks (especially
	* in a low-memory situation), we're better off ignoring
	* this failure than trying to recover.
	*/
	log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
	(unsigned long long)op->info.number, file, fl);
	}

	rv = notify(fl, 0);
	if (rv) {
	/* XXX: We need to cancel the fs lock here: */
	log_print("dlm_plock_callback: lock granted after lock request "
	"failed; dangling lock!\n");
	goto out;
	}

	out:
	dlm_release_plock_op(op);
	return rv;
	}

	int dlm_posix_unlock(dlm_lockspace_t lockspace, u64 number, struct file file,
	struct file_lock *fl)
	{
	struct dlm_ls *ls;
	struct plock_op *op;
	int rv;
	unsigned char fl_flags = fl->fl_flags;

	ls = dlm_find_lockspace_local(lockspace);
	if (!ls)
	return -EINVAL;

	op = kzalloc(sizeof(*op), GFP_NOFS);
	if (!op) {
	rv = -ENOMEM;
	goto out;
	}

	/* cause the vfs unlock to return ENOENT if lock is not found */
	fl->fl_flags \|= FL_EXISTS;

	rv = locks_lock_file_wait(file, fl);
	if (rv == -ENOENT) {
	rv = 0;
	goto out_free;
	}
	if (rv < 0) {
	log_error(ls, "dlm_posix_unlock: vfs unlock error %d %llx",
	rv, (unsigned long long)number);
	}

	op->info.optype = DLM_PLOCK_OP_UNLOCK;
	op->info.pid = fl->fl_pid;
	op->info.fsid = ls->ls_global_id;
	op->info.number = number;
	op->info.start = fl->fl_start;
	op->info.end = fl->fl_end;
	if (fl->fl_lmops && fl->fl_lmops->lm_grant)
	op->info.owner = (__u64) fl->fl_pid;
	else
	op->info.owner = (__u64)(long) fl->fl_owner;

	if (fl->fl_flags & FL_CLOSE) {
	op->info.flags \|= DLM_PLOCK_FL_CLOSE;
	send_op(op);
	rv = 0;
	goto out;
	}

	send_op(op);
	wait_event(recv_wq, (op->done != 0));

	spin_lock(&ops_lock);
	if (!list_empty(&op->list)) {
	log_error(ls, "dlm_posix_unlock: op on list %llx",
	(unsigned long long)number);
	list_del(&op->list);
	}
	spin_unlock(&ops_lock);

	rv = op->info.rv;

	if (rv == -ENOENT)
	rv = 0;

	out_free:
	dlm_release_plock_op(op);
	out:
	dlm_put_lockspace(ls);
	fl->fl_flags = fl_flags;
	return rv;
	}
	EXPORT_SYMBOL_GPL(dlm_posix_unlock);

	int dlm_posix_get(dlm_lockspace_t lockspace, u64 number, struct file file,
	struct file_lock *fl)
	{
	struct dlm_ls *ls;
	struct plock_op *op;
	int rv;

	ls = dlm_find_lockspace_local(lockspace);
	if (!ls)
	return -EINVAL;

	op = kzalloc(sizeof(*op), GFP_NOFS);
	if (!op) {
	rv = -ENOMEM;
	goto out;
	}

	op->info.optype = DLM_PLOCK_OP_GET;
	op->info.pid = fl->fl_pid;
	op->info.ex = (fl->fl_type == F_WRLCK);
	op->info.fsid = ls->ls_global_id;
	op->info.number = number;
	op->info.start = fl->fl_start;
	op->info.end = fl->fl_end;
	if (fl->fl_lmops && fl->fl_lmops->lm_grant)
	op->info.owner = (__u64) fl->fl_pid;
	else
	op->info.owner = (__u64)(long) fl->fl_owner;

	send_op(op);
	wait_event(recv_wq, (op->done != 0));

	spin_lock(&ops_lock);
	if (!list_empty(&op->list)) {
	log_error(ls, "dlm_posix_get: op on list %llx",
	(unsigned long long)number);
	list_del(&op->list);
	}
	spin_unlock(&ops_lock);

	/* info.rv from userspace is 1 for conflict, 0 for no-conflict,
	-ENOENT if there are no locks on the file */

	rv = op->info.rv;

	fl->fl_type = F_UNLCK;
	if (rv == -ENOENT)
	rv = 0;
	else if (rv > 0) {
	locks_init_lock(fl);
	fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
	fl->fl_flags = FL_POSIX;
	fl->fl_pid = op->info.pid;
	if (op->info.nodeid != dlm_our_nodeid())
	fl->fl_pid = -fl->fl_pid;
	fl->fl_start = op->info.start;
	fl->fl_end = op->info.end;
	rv = 0;
	}

	dlm_release_plock_op(op);
	out:
	dlm_put_lockspace(ls);
	return rv;
	}
	EXPORT_SYMBOL_GPL(dlm_posix_get);

	/* a read copies out one plock request from the send list */
	static ssize_t dev_read(struct file file, char __user u, size_t count,
	loff_t *ppos)
	{
	struct dlm_plock_info info;
	struct plock_op *op = NULL;

	if (count < sizeof(info))
	return -EINVAL;

	spin_lock(&ops_lock);
	if (!list_empty(&send_list)) {
	op = list_entry(send_list.next, struct plock_op, list);
	if (op->info.flags & DLM_PLOCK_FL_CLOSE)
	list_del(&op->list);
	else
	list_move_tail(&op->list, &recv_list);
	memcpy(&info, &op->info, sizeof(info));
	}
	spin_unlock(&ops_lock);

	if (!op)
	return -EAGAIN;

	/* there is no need to get a reply from userspace for unlocks
	that were generated by the vfs cleaning up for a close
	(the process did not make an unlock call). */

	if (op->info.flags & DLM_PLOCK_FL_CLOSE)
	dlm_release_plock_op(op);

	if (copy_to_user(u, &info, sizeof(info)))
	return -EFAULT;
	return sizeof(info);
	}

	/* a write copies in one plock result that should match a plock_op
	on the recv list */
	static ssize_t dev_write(struct file file, const char __user u, size_t count,
	loff_t *ppos)
	{
	struct plock_op op = NULL, iter;
	struct dlm_plock_info info;
	int do_callback = 0;

	if (count != sizeof(info))
	return -EINVAL;

	if (copy_from_user(&info, u, sizeof(info)))
	return -EFAULT;

	if (check_version(&info))
	return -EINVAL;

	/*
	* The results for waiting ops (SETLKW) can be returned in any
	* order, so match all fields to find the op. The results for
	* non-waiting ops are returned in the order that they were sent
	* to userspace, so match the result with the first non-waiting op.
	*/
	spin_lock(&ops_lock);
	if (info.wait) {
	list_for_each_entry(iter, &recv_list, list) {
	if (iter->info.fsid == info.fsid &&
	iter->info.number == info.number &&
	iter->info.owner == info.owner &&
	iter->info.pid == info.pid &&
	iter->info.start == info.start &&
	iter->info.end == info.end &&
	iter->info.ex == info.ex &&
	iter->info.wait) {
	op = iter;
	break;
	}
	}
	} else {
	list_for_each_entry(iter, &recv_list, list) {
	if (!iter->info.wait &&
	iter->info.fsid == info.fsid) {
	op = iter;
	break;
	}
	}
	}

	if (op) {
	/* Sanity check that op and info match. */
	if (info.wait)
	WARN_ON(op->info.optype != DLM_PLOCK_OP_LOCK);
	else
	WARN_ON(op->info.number != info.number \|\|
	op->info.owner != info.owner \|\|
	op->info.optype != info.optype);

	list_del_init(&op->list);
	memcpy(&op->info, &info, sizeof(info));
	if (op->data)
	do_callback = 1;
	else
	op->done = 1;
	}
	spin_unlock(&ops_lock);

	if (op) {
	if (do_callback)
	dlm_plock_callback(op);
	else
	wake_up(&recv_wq);
	} else
	log_print("%s: no op %x %llx", __func__,
	info.fsid, (unsigned long long)info.number);
	return count;
	}

	static unsigned int dev_poll(struct file file, poll_table wait)
	{
	unsigned int mask = 0;

	poll_wait(file, &send_wq, wait);

	spin_lock(&ops_lock);
	if (!list_empty(&send_list))
	mask = POLLIN \| POLLRDNORM;
	spin_unlock(&ops_lock);

	return mask;
	}

	static const struct file_operations dev_fops = {
	.read = dev_read,
	.write = dev_write,
	.poll = dev_poll,
	.owner = THIS_MODULE,
	.llseek = noop_llseek,
	};

	static struct miscdevice plock_dev_misc = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = DLM_PLOCK_MISC_NAME,
	.fops = &dev_fops
	};

	int dlm_plock_init(void)
	{
	int rv;

	spin_lock_init(&ops_lock);
	INIT_LIST_HEAD(&send_list);
	INIT_LIST_HEAD(&recv_list);
	init_waitqueue_head(&send_wq);
	init_waitqueue_head(&recv_wq);

	rv = misc_register(&plock_dev_misc);
	if (rv)
	log_print("dlm_plock_init: misc_register failed %d", rv);
	return rv;
	}

	void dlm_plock_exit(void)
	{
	misc_deregister(&plock_dev_misc);
	}