Adding upstream version 6.6.15.upstream/6.6.15

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

1 files changed, 1046 insertions, 0 deletions

diff --git a/fs/dlm/user.c b/fs/dlm/user.c
new file mode 100644
index 0000000000..695e691b38
--- /dev/null
+++ b/fs/dlm/user.c
@@ -0,0 +1,1046 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2006-2010 Red Hat, Inc.  All rights reserved.
+ */
+
+#include <linux/miscdevice.h>
+#include <linux/init.h>
+#include <linux/wait.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/signal.h>
+#include <linux/spinlock.h>
+#include <linux/dlm.h>
+#include <linux/dlm_device.h>
+#include <linux/slab.h>
+#include <linux/sched/signal.h>
+
+#include <trace/events/dlm.h>
+
+#include "dlm_internal.h"
+#include "lockspace.h"
+#include "lock.h"
+#include "lvb_table.h"
+#include "user.h"
+#include "ast.h"
+#include "config.h"
+#include "memory.h"
+
+static const char name_prefix[] = "dlm";
+static const struct file_operations device_fops;
+static atomic_t dlm_monitor_opened;
+static int dlm_monitor_unused = 1;
+
+#ifdef CONFIG_COMPAT
+
+struct dlm_lock_params32 {
+	__u8 mode;
+	__u8 namelen;
+	__u16 unused;
+	__u32 flags;
+	__u32 lkid;
+	__u32 parent;
+	__u64 xid;
+	__u64 timeout;
+	__u32 castparam;
+	__u32 castaddr;
+	__u32 bastparam;
+	__u32 bastaddr;
+	__u32 lksb;
+	char lvb[DLM_USER_LVB_LEN];
+	char name[];
+};
+
+struct dlm_write_request32 {
+	__u32 version[3];
+	__u8 cmd;
+	__u8 is64bit;
+	__u8 unused[2];
+
+	union  {
+		struct dlm_lock_params32 lock;
+		struct dlm_lspace_params lspace;
+		struct dlm_purge_params purge;
+	} i;
+};
+
+struct dlm_lksb32 {
+	__u32 sb_status;
+	__u32 sb_lkid;
+	__u8 sb_flags;
+	__u32 sb_lvbptr;
+};
+
+struct dlm_lock_result32 {
+	__u32 version[3];
+	__u32 length;
+	__u32 user_astaddr;
+	__u32 user_astparam;
+	__u32 user_lksb;
+	struct dlm_lksb32 lksb;
+	__u8 bast_mode;
+	__u8 unused[3];
+	/* Offsets may be zero if no data is present */
+	__u32 lvb_offset;
+};
+
+static void compat_input(struct dlm_write_request *kb,
+			 struct dlm_write_request32 *kb32,
+			 int namelen)
+{
+	kb->version[0] = kb32->version[0];
+	kb->version[1] = kb32->version[1];
+	kb->version[2] = kb32->version[2];
+
+	kb->cmd = kb32->cmd;
+	kb->is64bit = kb32->is64bit;
+	if (kb->cmd == DLM_USER_CREATE_LOCKSPACE ||
+	    kb->cmd == DLM_USER_REMOVE_LOCKSPACE) {
+		kb->i.lspace.flags = kb32->i.lspace.flags;
+		kb->i.lspace.minor = kb32->i.lspace.minor;
+		memcpy(kb->i.lspace.name, kb32->i.lspace.name, namelen);
+	} else if (kb->cmd == DLM_USER_PURGE) {
+		kb->i.purge.nodeid = kb32->i.purge.nodeid;
+		kb->i.purge.pid = kb32->i.purge.pid;
+	} else {
+		kb->i.lock.mode = kb32->i.lock.mode;
+		kb->i.lock.namelen = kb32->i.lock.namelen;
+		kb->i.lock.flags = kb32->i.lock.flags;
+		kb->i.lock.lkid = kb32->i.lock.lkid;
+		kb->i.lock.parent = kb32->i.lock.parent;
+		kb->i.lock.xid = kb32->i.lock.xid;
+		kb->i.lock.timeout = kb32->i.lock.timeout;
+		kb->i.lock.castparam = (__user void *)(long)kb32->i.lock.castparam;
+		kb->i.lock.castaddr = (__user void *)(long)kb32->i.lock.castaddr;
+		kb->i.lock.bastparam = (__user void *)(long)kb32->i.lock.bastparam;
+		kb->i.lock.bastaddr = (__user void *)(long)kb32->i.lock.bastaddr;
+		kb->i.lock.lksb = (__user void *)(long)kb32->i.lock.lksb;
+		memcpy(kb->i.lock.lvb, kb32->i.lock.lvb, DLM_USER_LVB_LEN);
+		memcpy(kb->i.lock.name, kb32->i.lock.name, namelen);
+	}
+}
+
+static void compat_output(struct dlm_lock_result *res,
+			  struct dlm_lock_result32 *res32)
+{
+	memset(res32, 0, sizeof(*res32));
+
+	res32->version[0] = res->version[0];
+	res32->version[1] = res->version[1];
+	res32->version[2] = res->version[2];
+
+	res32->user_astaddr = (__u32)(__force long)res->user_astaddr;
+	res32->user_astparam = (__u32)(__force long)res->user_astparam;
+	res32->user_lksb = (__u32)(__force long)res->user_lksb;
+	res32->bast_mode = res->bast_mode;
+
+	res32->lvb_offset = res->lvb_offset;
+	res32->length = res->length;
+
+	res32->lksb.sb_status = res->lksb.sb_status;
+	res32->lksb.sb_flags = res->lksb.sb_flags;
+	res32->lksb.sb_lkid = res->lksb.sb_lkid;
+	res32->lksb.sb_lvbptr = (__u32)(long)res->lksb.sb_lvbptr;
+}
+#endif
+
+/* should held proc->asts_spin lock */
+void dlm_purge_lkb_callbacks(struct dlm_lkb *lkb)
+{
+	struct dlm_callback *cb, *safe;
+
+	list_for_each_entry_safe(cb, safe, &lkb->lkb_callbacks, list) {
+		list_del(&cb->list);
+		kref_put(&cb->ref, dlm_release_callback);
+	}
+
+	clear_bit(DLM_IFL_CB_PENDING_BIT, &lkb->lkb_iflags);
+
+	/* invalidate */
+	dlm_callback_set_last_ptr(&lkb->lkb_last_cast, NULL);
+	dlm_callback_set_last_ptr(&lkb->lkb_last_cb, NULL);
+	lkb->lkb_last_bast_mode = -1;
+}
+
+/* Figure out if this lock is at the end of its life and no longer
+   available for the application to use.  The lkb still exists until
+   the final ast is read.  A lock becomes EOL in three situations:
+     1. a noqueue request fails with EAGAIN
+     2. an unlock completes with EUNLOCK
+     3. a cancel of a waiting request completes with ECANCEL/EDEADLK
+   An EOL lock needs to be removed from the process's list of locks.
+   And we can't allow any new operation on an EOL lock.  This is
+   not related to the lifetime of the lkb struct which is managed
+   entirely by refcount. */
+
+static int lkb_is_endoflife(int mode, int status)
+{
+	switch (status) {
+	case -DLM_EUNLOCK:
+		return 1;
+	case -DLM_ECANCEL:
+	case -ETIMEDOUT:
+	case -EDEADLK:
+	case -EAGAIN:
+		if (mode == DLM_LOCK_IV)
+			return 1;
+		break;
+	}
+	return 0;
+}
+
+/* we could possibly check if the cancel of an orphan has resulted in the lkb
+   being removed and then remove that lkb from the orphans list and free it */
+
+void dlm_user_add_ast(struct dlm_lkb *lkb, uint32_t flags, int mode,
+		      int status, uint32_t sbflags)
+{
+	struct dlm_ls *ls;
+	struct dlm_user_args *ua;
+	struct dlm_user_proc *proc;
+	int rv;
+
+	if (test_bit(DLM_DFL_ORPHAN_BIT, &lkb->lkb_dflags) ||
+	    test_bit(DLM_IFL_DEAD_BIT, &lkb->lkb_iflags))
+		return;
+
+	ls = lkb->lkb_resource->res_ls;
+	spin_lock(&ls->ls_clear_proc_locks);
+
+	/* If ORPHAN/DEAD flag is set, it means the process is dead so an ast
+	   can't be delivered.  For ORPHAN's, dlm_clear_proc_locks() freed
+	   lkb->ua so we can't try to use it.  This second check is necessary
+	   for cases where a completion ast is received for an operation that
+	   began before clear_proc_locks did its cancel/unlock. */
+
+	if (test_bit(DLM_DFL_ORPHAN_BIT, &lkb->lkb_dflags) ||
+	    test_bit(DLM_IFL_DEAD_BIT, &lkb->lkb_iflags))
+		goto out;
+
+	DLM_ASSERT(lkb->lkb_ua, dlm_print_lkb(lkb););
+	ua = lkb->lkb_ua;
+	proc = ua->proc;
+
+	if ((flags & DLM_CB_BAST) && ua->bastaddr == NULL)
+		goto out;
+
+	if ((flags & DLM_CB_CAST) && lkb_is_endoflife(mode, status))
+		set_bit(DLM_IFL_ENDOFLIFE_BIT, &lkb->lkb_iflags);
+
+	spin_lock(&proc->asts_spin);
+
+	rv = dlm_enqueue_lkb_callback(lkb, flags, mode, status, sbflags);
+	switch (rv) {
+	case DLM_ENQUEUE_CALLBACK_FAILURE:
+		spin_unlock(&proc->asts_spin);
+		WARN_ON_ONCE(1);
+		goto out;
+	case DLM_ENQUEUE_CALLBACK_NEED_SCHED:
+		kref_get(&lkb->lkb_ref);
+		list_add_tail(&lkb->lkb_cb_list, &proc->asts);
+		wake_up_interruptible(&proc->wait);
+		break;
+	case DLM_ENQUEUE_CALLBACK_SUCCESS:
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+	spin_unlock(&proc->asts_spin);
+
+	if (test_bit(DLM_IFL_ENDOFLIFE_BIT, &lkb->lkb_iflags)) {
+		/* N.B. spin_lock locks_spin, not asts_spin */
+		spin_lock(&proc->locks_spin);
+		if (!list_empty(&lkb->lkb_ownqueue)) {
+			list_del_init(&lkb->lkb_ownqueue);
+			dlm_put_lkb(lkb);
+		}
+		spin_unlock(&proc->locks_spin);
+	}
+ out:
+	spin_unlock(&ls->ls_clear_proc_locks);
+}
+
+static int device_user_lock(struct dlm_user_proc *proc,
+			    struct dlm_lock_params *params)
+{
+	struct dlm_ls *ls;
+	struct dlm_user_args *ua;
+	uint32_t lkid;
+	int error = -ENOMEM;
+
+	ls = dlm_find_lockspace_local(proc->lockspace);
+	if (!ls)
+		return -ENOENT;
+
+	if (!params->castaddr || !params->lksb) {
+		error = -EINVAL;
+		goto out;
+	}
+
+	ua = kzalloc(sizeof(struct dlm_user_args), GFP_NOFS);
+	if (!ua)
+		goto out;
+	ua->proc = proc;
+	ua->user_lksb = params->lksb;
+	ua->castparam = params->castparam;
+	ua->castaddr = params->castaddr;
+	ua->bastparam = params->bastparam;
+	ua->bastaddr = params->bastaddr;
+	ua->xid = params->xid;
+
+	if (params->flags & DLM_LKF_CONVERT) {
+		error = dlm_user_convert(ls, ua,
+					 params->mode, params->flags,
+					 params->lkid, params->lvb);
+	} else if (params->flags & DLM_LKF_ORPHAN) {
+		error = dlm_user_adopt_orphan(ls, ua,
+					 params->mode, params->flags,
+					 params->name, params->namelen,
+					 &lkid);
+		if (!error)
+			error = lkid;
+	} else {
+		error = dlm_user_request(ls, ua,
+					 params->mode, params->flags,
+					 params->name, params->namelen);
+		if (!error)
+			error = ua->lksb.sb_lkid;
+	}
+ out:
+	dlm_put_lockspace(ls);
+	return error;
+}
+
+static int device_user_unlock(struct dlm_user_proc *proc,
+			      struct dlm_lock_params *params)
+{
+	struct dlm_ls *ls;
+	struct dlm_user_args *ua;
+	int error = -ENOMEM;
+
+	ls = dlm_find_lockspace_local(proc->lockspace);
+	if (!ls)
+		return -ENOENT;
+
+	ua = kzalloc(sizeof(struct dlm_user_args), GFP_NOFS);
+	if (!ua)
+		goto out;
+	ua->proc = proc;
+	ua->user_lksb = params->lksb;
+	ua->castparam = params->castparam;
+	ua->castaddr = params->castaddr;
+
+	if (params->flags & DLM_LKF_CANCEL)
+		error = dlm_user_cancel(ls, ua, params->flags, params->lkid);
+	else
+		error = dlm_user_unlock(ls, ua, params->flags, params->lkid,
+					params->lvb);
+ out:
+	dlm_put_lockspace(ls);
+	return error;
+}
+
+static int device_user_deadlock(struct dlm_user_proc *proc,
+				struct dlm_lock_params *params)
+{
+	struct dlm_ls *ls;
+	int error;
+
+	ls = dlm_find_lockspace_local(proc->lockspace);
+	if (!ls)
+		return -ENOENT;
+
+	error = dlm_user_deadlock(ls, params->flags, params->lkid);
+
+	dlm_put_lockspace(ls);
+	return error;
+}
+
+static int dlm_device_register(struct dlm_ls *ls, char *name)
+{
+	int error, len;
+
+	/* The device is already registered.  This happens when the
+	   lockspace is created multiple times from userspace. */
+	if (ls->ls_device.name)
+		return 0;
+
+	error = -ENOMEM;
+	len = strlen(name) + strlen(name_prefix) + 2;
+	ls->ls_device.name = kzalloc(len, GFP_NOFS);
+	if (!ls->ls_device.name)
+		goto fail;
+
+	snprintf((char *)ls->ls_device.name, len, "%s_%s", name_prefix,
+		 name);
+	ls->ls_device.fops = &device_fops;
+	ls->ls_device.minor = MISC_DYNAMIC_MINOR;
+
+	error = misc_register(&ls->ls_device);
+	if (error) {
+		kfree(ls->ls_device.name);
+		/* this has to be set to NULL
+		 * to avoid a double-free in dlm_device_deregister
+		 */
+		ls->ls_device.name = NULL;
+	}
+fail:
+	return error;
+}
+
+int dlm_device_deregister(struct dlm_ls *ls)
+{
+	/* The device is not registered.  This happens when the lockspace
+	   was never used from userspace, or when device_create_lockspace()
+	   calls dlm_release_lockspace() after the register fails. */
+	if (!ls->ls_device.name)
+		return 0;
+
+	misc_deregister(&ls->ls_device);
+	kfree(ls->ls_device.name);
+	return 0;
+}
+
+static int device_user_purge(struct dlm_user_proc *proc,
+			     struct dlm_purge_params *params)
+{
+	struct dlm_ls *ls;
+	int error;
+
+	ls = dlm_find_lockspace_local(proc->lockspace);
+	if (!ls)
+		return -ENOENT;
+
+	error = dlm_user_purge(ls, proc, params->nodeid, params->pid);
+
+	dlm_put_lockspace(ls);
+	return error;
+}
+
+static int device_create_lockspace(struct dlm_lspace_params *params)
+{
+	dlm_lockspace_t *lockspace;
+	struct dlm_ls *ls;
+	int error;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	error = dlm_new_user_lockspace(params->name, dlm_config.ci_cluster_name,
+				       params->flags, DLM_USER_LVB_LEN, NULL,
+				       NULL, NULL, &lockspace);
+	if (error)
+		return error;
+
+	ls = dlm_find_lockspace_local(lockspace);
+	if (!ls)
+		return -ENOENT;
+
+	error = dlm_device_register(ls, params->name);
+	dlm_put_lockspace(ls);
+
+	if (error)
+		dlm_release_lockspace(lockspace, 0);
+	else
+		error = ls->ls_device.minor;
+
+	return error;
+}
+
+static int device_remove_lockspace(struct dlm_lspace_params *params)
+{
+	dlm_lockspace_t *lockspace;
+	struct dlm_ls *ls;
+	int error, force = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ls = dlm_find_lockspace_device(params->minor);
+	if (!ls)
+		return -ENOENT;
+
+	if (params->flags & DLM_USER_LSFLG_FORCEFREE)
+		force = 2;
+
+	lockspace = ls->ls_local_handle;
+	dlm_put_lockspace(ls);
+
+	/* The final dlm_release_lockspace waits for references to go to
+	   zero, so all processes will need to close their device for the
+	   ls before the release will proceed.  release also calls the
+	   device_deregister above.  Converting a positive return value
+	   from release to zero means that userspace won't know when its
+	   release was the final one, but it shouldn't need to know. */
+
+	error = dlm_release_lockspace(lockspace, force);
+	if (error > 0)
+		error = 0;
+	return error;
+}
+
+/* Check the user's version matches ours */
+static int check_version(struct dlm_write_request *req)
+{
+	if (req->version[0] != DLM_DEVICE_VERSION_MAJOR ||
+	    (req->version[0] == DLM_DEVICE_VERSION_MAJOR &&
+	     req->version[1] > DLM_DEVICE_VERSION_MINOR)) {
+
+		printk(KERN_DEBUG "dlm: process %s (%d) version mismatch "
+		       "user (%d.%d.%d) kernel (%d.%d.%d)\n",
+		       current->comm,
+		       task_pid_nr(current),
+		       req->version[0],
+		       req->version[1],
+		       req->version[2],
+		       DLM_DEVICE_VERSION_MAJOR,
+		       DLM_DEVICE_VERSION_MINOR,
+		       DLM_DEVICE_VERSION_PATCH);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/*
+ * device_write
+ *
+ *   device_user_lock
+ *     dlm_user_request -> request_lock
+ *     dlm_user_convert -> convert_lock
+ *
+ *   device_user_unlock
+ *     dlm_user_unlock -> unlock_lock
+ *     dlm_user_cancel -> cancel_lock
+ *
+ *   device_create_lockspace
+ *     dlm_new_lockspace
+ *
+ *   device_remove_lockspace
+ *     dlm_release_lockspace
+ */
+
+/* a write to a lockspace device is a lock or unlock request, a write
+   to the control device is to create/remove a lockspace */
+
+static ssize_t device_write(struct file *file, const char __user *buf,
+			    size_t count, loff_t *ppos)
+{
+	struct dlm_user_proc *proc = file->private_data;
+	struct dlm_write_request *kbuf;
+	int error;
+
+#ifdef CONFIG_COMPAT
+	if (count < sizeof(struct dlm_write_request32))
+#else
+	if (count < sizeof(struct dlm_write_request))
+#endif
+		return -EINVAL;
+
+	/*
+	 * can't compare against COMPAT/dlm_write_request32 because
+	 * we don't yet know if is64bit is zero
+	 */
+	if (count > sizeof(struct dlm_write_request) + DLM_RESNAME_MAXLEN)
+		return -EINVAL;
+
+	kbuf = memdup_user_nul(buf, count);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	if (check_version(kbuf)) {
+		error = -EBADE;
+		goto out_free;
+	}
+
+#ifdef CONFIG_COMPAT
+	if (!kbuf->is64bit) {
+		struct dlm_write_request32 *k32buf;
+		int namelen = 0;
+
+		if (count > sizeof(struct dlm_write_request32))
+			namelen = count - sizeof(struct dlm_write_request32);
+
+		k32buf = (struct dlm_write_request32 *)kbuf;
+
+		/* add 1 after namelen so that the name string is terminated */
+		kbuf = kzalloc(sizeof(struct dlm_write_request) + namelen + 1,
+			       GFP_NOFS);
+		if (!kbuf) {
+			kfree(k32buf);
+			return -ENOMEM;
+		}
+
+		if (proc)
+			set_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags);
+
+		compat_input(kbuf, k32buf, namelen);
+		kfree(k32buf);
+	}
+#endif
+
+	/* do we really need this? can a write happen after a close? */
+	if ((kbuf->cmd == DLM_USER_LOCK || kbuf->cmd == DLM_USER_UNLOCK) &&
+	    (proc && test_bit(DLM_PROC_FLAGS_CLOSING, &proc->flags))) {
+		error = -EINVAL;
+		goto out_free;
+	}
+
+	error = -EINVAL;
+
+	switch (kbuf->cmd)
+	{
+	case DLM_USER_LOCK:
+		if (!proc) {
+			log_print("no locking on control device");
+			goto out_free;
+		}
+		error = device_user_lock(proc, &kbuf->i.lock);
+		break;
+
+	case DLM_USER_UNLOCK:
+		if (!proc) {
+			log_print("no locking on control device");
+			goto out_free;
+		}
+		error = device_user_unlock(proc, &kbuf->i.lock);
+		break;
+
+	case DLM_USER_DEADLOCK:
+		if (!proc) {
+			log_print("no locking on control device");
+			goto out_free;
+		}
+		error = device_user_deadlock(proc, &kbuf->i.lock);
+		break;
+
+	case DLM_USER_CREATE_LOCKSPACE:
+		if (proc) {
+			log_print("create/remove only on control device");
+			goto out_free;
+		}
+		error = device_create_lockspace(&kbuf->i.lspace);
+		break;
+
+	case DLM_USER_REMOVE_LOCKSPACE:
+		if (proc) {
+			log_print("create/remove only on control device");
+			goto out_free;
+		}
+		error = device_remove_lockspace(&kbuf->i.lspace);
+		break;
+
+	case DLM_USER_PURGE:
+		if (!proc) {
+			log_print("no locking on control device");
+			goto out_free;
+		}
+		error = device_user_purge(proc, &kbuf->i.purge);
+		break;
+
+	default:
+		log_print("Unknown command passed to DLM device : %d\n",
+			  kbuf->cmd);
+	}
+
+ out_free:
+	kfree(kbuf);
+	return error;
+}
+
+/* Every process that opens the lockspace device has its own "proc" structure
+   hanging off the open file that's used to keep track of locks owned by the
+   process and asts that need to be delivered to the process. */
+
+static int device_open(struct inode *inode, struct file *file)
+{
+	struct dlm_user_proc *proc;
+	struct dlm_ls *ls;
+
+	ls = dlm_find_lockspace_device(iminor(inode));
+	if (!ls)
+		return -ENOENT;
+
+	proc = kzalloc(sizeof(struct dlm_user_proc), GFP_NOFS);
+	if (!proc) {
+		dlm_put_lockspace(ls);
+		return -ENOMEM;
+	}
+
+	proc->lockspace = ls->ls_local_handle;
+	INIT_LIST_HEAD(&proc->asts);
+	INIT_LIST_HEAD(&proc->locks);
+	INIT_LIST_HEAD(&proc->unlocking);
+	spin_lock_init(&proc->asts_spin);
+	spin_lock_init(&proc->locks_spin);
+	init_waitqueue_head(&proc->wait);
+	file->private_data = proc;
+
+	return 0;
+}
+
+static int device_close(struct inode *inode, struct file *file)
+{
+	struct dlm_user_proc *proc = file->private_data;
+	struct dlm_ls *ls;
+
+	ls = dlm_find_lockspace_local(proc->lockspace);
+	if (!ls)
+		return -ENOENT;
+
+	set_bit(DLM_PROC_FLAGS_CLOSING, &proc->flags);
+
+	dlm_clear_proc_locks(ls, proc);
+
+	/* at this point no more lkb's should exist for this lockspace,
+	   so there's no chance of dlm_user_add_ast() being called and
+	   looking for lkb->ua->proc */
+
+	kfree(proc);
+	file->private_data = NULL;
+
+	dlm_put_lockspace(ls);
+	dlm_put_lockspace(ls);  /* for the find in device_open() */
+
+	/* FIXME: AUTOFREE: if this ls is no longer used do
+	   device_remove_lockspace() */
+
+	return 0;
+}
+
+static int copy_result_to_user(struct dlm_user_args *ua, int compat,
+			       uint32_t flags, int mode, int copy_lvb,
+			       char __user *buf, size_t count)
+{
+#ifdef CONFIG_COMPAT
+	struct dlm_lock_result32 result32;
+#endif
+	struct dlm_lock_result result;
+	void *resultptr;
+	int error=0;
+	int len;
+	int struct_len;
+
+	memset(&result, 0, sizeof(struct dlm_lock_result));
+	result.version[0] = DLM_DEVICE_VERSION_MAJOR;
+	result.version[1] = DLM_DEVICE_VERSION_MINOR;
+	result.version[2] = DLM_DEVICE_VERSION_PATCH;
+	memcpy(&result.lksb, &ua->lksb, offsetof(struct dlm_lksb, sb_lvbptr));
+	result.user_lksb = ua->user_lksb;
+
+	/* FIXME: dlm1 provides for the user's bastparam/addr to not be updated
+	   in a conversion unless the conversion is successful.  See code
+	   in dlm_user_convert() for updating ua from ua_tmp.  OpenVMS, though,
+	   notes that a new blocking AST address and parameter are set even if
+	   the conversion fails, so maybe we should just do that. */
+
+	if (flags & DLM_CB_BAST) {
+		result.user_astaddr = ua->bastaddr;
+		result.user_astparam = ua->bastparam;
+		result.bast_mode = mode;
+	} else {
+		result.user_astaddr = ua->castaddr;
+		result.user_astparam = ua->castparam;
+	}
+
+#ifdef CONFIG_COMPAT
+	if (compat)
+		len = sizeof(struct dlm_lock_result32);
+	else
+#endif
+		len = sizeof(struct dlm_lock_result);
+	struct_len = len;
+
+	/* copy lvb to userspace if there is one, it's been updated, and
+	   the user buffer has space for it */
+
+	if (copy_lvb && ua->lksb.sb_lvbptr && count >= len + DLM_USER_LVB_LEN) {
+		if (copy_to_user(buf+len, ua->lksb.sb_lvbptr,
+				 DLM_USER_LVB_LEN)) {
+			error = -EFAULT;
+			goto out;
+		}
+
+		result.lvb_offset = len;
+		len += DLM_USER_LVB_LEN;
+	}
+
+	result.length = len;
+	resultptr = &result;
+#ifdef CONFIG_COMPAT
+	if (compat) {
+		compat_output(&result, &result32);
+		resultptr = &result32;
+	}
+#endif
+
+	if (copy_to_user(buf, resultptr, struct_len))
+		error = -EFAULT;
+	else
+		error = len;
+ out:
+	return error;
+}
+
+static int copy_version_to_user(char __user *buf, size_t count)
+{
+	struct dlm_device_version ver;
+
+	memset(&ver, 0, sizeof(struct dlm_device_version));
+	ver.version[0] = DLM_DEVICE_VERSION_MAJOR;
+	ver.version[1] = DLM_DEVICE_VERSION_MINOR;
+	ver.version[2] = DLM_DEVICE_VERSION_PATCH;
+
+	if (copy_to_user(buf, &ver, sizeof(struct dlm_device_version)))
+		return -EFAULT;
+	return sizeof(struct dlm_device_version);
+}
+
+/* a read returns a single ast described in a struct dlm_lock_result */
+
+static ssize_t device_read(struct file *file, char __user *buf, size_t count,
+			   loff_t *ppos)
+{
+	struct dlm_user_proc *proc = file->private_data;
+	struct dlm_lkb *lkb;
+	DECLARE_WAITQUEUE(wait, current);
+	struct dlm_callback *cb;
+	int rv, copy_lvb = 0;
+	int old_mode, new_mode;
+
+	if (count == sizeof(struct dlm_device_version)) {
+		rv = copy_version_to_user(buf, count);
+		return rv;
+	}
+
+	if (!proc) {
+		log_print("non-version read from control device %zu", count);
+		return -EINVAL;
+	}
+
+#ifdef CONFIG_COMPAT
+	if (count < sizeof(struct dlm_lock_result32))
+#else
+	if (count < sizeof(struct dlm_lock_result))
+#endif
+		return -EINVAL;
+
+ try_another:
+
+	/* do we really need this? can a read happen after a close? */
+	if (test_bit(DLM_PROC_FLAGS_CLOSING, &proc->flags))
+		return -EINVAL;
+
+	spin_lock(&proc->asts_spin);
+	if (list_empty(&proc->asts)) {
+		if (file->f_flags & O_NONBLOCK) {
+			spin_unlock(&proc->asts_spin);
+			return -EAGAIN;
+		}
+
+		add_wait_queue(&proc->wait, &wait);
+
+	repeat:
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (list_empty(&proc->asts) && !signal_pending(current)) {
+			spin_unlock(&proc->asts_spin);
+			schedule();
+			spin_lock(&proc->asts_spin);
+			goto repeat;
+		}
+		set_current_state(TASK_RUNNING);
+		remove_wait_queue(&proc->wait, &wait);
+
+		if (signal_pending(current)) {
+			spin_unlock(&proc->asts_spin);
+			return -ERESTARTSYS;
+		}
+	}
+
+	/* if we empty lkb_callbacks, we don't want to unlock the spinlock
+	   without removing lkb_cb_list; so empty lkb_cb_list is always
+	   consistent with empty lkb_callbacks */
+
+	lkb = list_first_entry(&proc->asts, struct dlm_lkb, lkb_cb_list);
+
+	/* rem_lkb_callback sets a new lkb_last_cast */
+	old_mode = lkb->lkb_last_cast->mode;
+
+	rv = dlm_dequeue_lkb_callback(lkb, &cb);
+	switch (rv) {
+	case DLM_DEQUEUE_CALLBACK_EMPTY:
+		/* this shouldn't happen; lkb should have been removed from
+		 * list when last item was dequeued
+		 */
+		log_print("dlm_rem_lkb_callback empty %x", lkb->lkb_id);
+		list_del_init(&lkb->lkb_cb_list);
+		spin_unlock(&proc->asts_spin);
+		/* removes ref for proc->asts, may cause lkb to be freed */
+		dlm_put_lkb(lkb);
+		WARN_ON_ONCE(1);
+		goto try_another;
+	case DLM_DEQUEUE_CALLBACK_LAST:
+		list_del_init(&lkb->lkb_cb_list);
+		clear_bit(DLM_IFL_CB_PENDING_BIT, &lkb->lkb_iflags);
+		break;
+	case DLM_DEQUEUE_CALLBACK_SUCCESS:
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+	spin_unlock(&proc->asts_spin);
+
+	if (cb->flags & DLM_CB_BAST) {
+		trace_dlm_bast(lkb->lkb_resource->res_ls, lkb, cb->mode);
+	} else if (cb->flags & DLM_CB_CAST) {
+		new_mode = cb->mode;
+
+		if (!cb->sb_status && lkb->lkb_lksb->sb_lvbptr &&
+		    dlm_lvb_operations[old_mode + 1][new_mode + 1])
+			copy_lvb = 1;
+
+		lkb->lkb_lksb->sb_status = cb->sb_status;
+		lkb->lkb_lksb->sb_flags = cb->sb_flags;
+		trace_dlm_ast(lkb->lkb_resource->res_ls, lkb);
+	}
+
+	rv = copy_result_to_user(lkb->lkb_ua,
+				 test_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags),
+				 cb->flags, cb->mode, copy_lvb, buf, count);
+
+	kref_put(&cb->ref, dlm_release_callback);
+
+	/* removes ref for proc->asts, may cause lkb to be freed */
+	if (rv == DLM_DEQUEUE_CALLBACK_LAST)
+		dlm_put_lkb(lkb);
+
+	return rv;
+}
+
+static __poll_t device_poll(struct file *file, poll_table *wait)
+{
+	struct dlm_user_proc *proc = file->private_data;
+
+	poll_wait(file, &proc->wait, wait);
+
+	spin_lock(&proc->asts_spin);
+	if (!list_empty(&proc->asts)) {
+		spin_unlock(&proc->asts_spin);
+		return EPOLLIN | EPOLLRDNORM;
+	}
+	spin_unlock(&proc->asts_spin);
+	return 0;
+}
+
+int dlm_user_daemon_available(void)
+{
+	/* dlm_controld hasn't started (or, has started, but not
+	   properly populated configfs) */
+
+	if (!dlm_our_nodeid())
+		return 0;
+
+	/* This is to deal with versions of dlm_controld that don't
+	   know about the monitor device.  We assume that if the
+	   dlm_controld was started (above), but the monitor device
+	   was never opened, that it's an old version.  dlm_controld
+	   should open the monitor device before populating configfs. */
+
+	if (dlm_monitor_unused)
+		return 1;
+
+	return atomic_read(&dlm_monitor_opened) ? 1 : 0;
+}
+
+static int ctl_device_open(struct inode *inode, struct file *file)
+{
+	file->private_data = NULL;
+	return 0;
+}
+
+static int ctl_device_close(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+static int monitor_device_open(struct inode *inode, struct file *file)
+{
+	atomic_inc(&dlm_monitor_opened);
+	dlm_monitor_unused = 0;
+	return 0;
+}
+
+static int monitor_device_close(struct inode *inode, struct file *file)
+{
+	if (atomic_dec_and_test(&dlm_monitor_opened))
+		dlm_stop_lockspaces();
+	return 0;
+}
+
+static const struct file_operations device_fops = {
+	.open    = device_open,
+	.release = device_close,
+	.read    = device_read,
+	.write   = device_write,
+	.poll    = device_poll,
+	.owner   = THIS_MODULE,
+	.llseek  = noop_llseek,
+};
+
+static const struct file_operations ctl_device_fops = {
+	.open    = ctl_device_open,
+	.release = ctl_device_close,
+	.read    = device_read,
+	.write   = device_write,
+	.owner   = THIS_MODULE,
+	.llseek  = noop_llseek,
+};
+
+static struct miscdevice ctl_device = {
+	.name  = "dlm-control",
+	.fops  = &ctl_device_fops,
+	.minor = MISC_DYNAMIC_MINOR,
+};
+
+static const struct file_operations monitor_device_fops = {
+	.open    = monitor_device_open,
+	.release = monitor_device_close,
+	.owner   = THIS_MODULE,
+	.llseek  = noop_llseek,
+};
+
+static struct miscdevice monitor_device = {
+	.name  = "dlm-monitor",
+	.fops  = &monitor_device_fops,
+	.minor = MISC_DYNAMIC_MINOR,
+};
+
+int __init dlm_user_init(void)
+{
+	int error;
+
+	atomic_set(&dlm_monitor_opened, 0);
+
+	error = misc_register(&ctl_device);
+	if (error) {
+		log_print("misc_register failed for control device");
+		goto out;
+	}
+
+	error = misc_register(&monitor_device);
+	if (error) {
+		log_print("misc_register failed for monitor device");
+		misc_deregister(&ctl_device);
+	}
+ out:
+	return error;
+}
+
+void dlm_user_exit(void)
+{
+	misc_deregister(&ctl_device);
+	misc_deregister(&monitor_device);
+}
+