fs/ocfs2/dlm/dlmthread.c - kernel/msm-4.9 - Gitiles

 /* -*- mode: c; c-basic-offset: 8; -*-
  * vim: noexpandtab sw=8 ts=8 sts=0:
  *
  * dlmthread.c
  *
  * standalone DLM module
  *
  * Copyright (C) 2004 Oracle.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU General Public
  * License along with this program; if not, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 021110-1307, USA.
  *
  */


 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/types.h>
 #include <linux/highmem.h>
 #include <linux/init.h>
 #include <linux/sysctl.h>
 #include <linux/random.h>
 #include <linux/blkdev.h>
 #include <linux/socket.h>
 #include <linux/inet.h>
 #include <linux/timer.h>
 #include <linux/kthread.h>
 #include <linux/delay.h>


 #include "cluster/heartbeat.h"
 #include "cluster/nodemanager.h"
 #include "cluster/tcp.h"

 #include "dlmapi.h"
 #include "dlmcommon.h"
 #include "dlmdomain.h"

 #define MLOG_MASK_PREFIX (ML_DLM|ML_DLM_THREAD)
 #include "cluster/masklog.h"

 static int dlm_thread(void *data);
 static void dlm_flush_asts(struct dlm_ctxt *dlm);

 #define dlm_lock_is_remote(dlm, lock)     ((lock)->ml.node != (dlm)->node_num)

 /* will exit holding res->spinlock, but may drop in function */
 /* waits until flags are cleared on res->state */
 void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags)
 {
 	DECLARE_WAITQUEUE(wait, current);

 	assert_spin_locked(&res->spinlock);

 	add_wait_queue(&res->wq, &wait);
 repeat:
 	set_current_state(TASK_UNINTERRUPTIBLE);
 	if (res->state & flags) {
 		spin_unlock(&res->spinlock);
 		schedule();
 		spin_lock(&res->spinlock);
 		goto repeat;
 	}
 	remove_wait_queue(&res->wq, &wait);
 	__set_current_state(TASK_RUNNING);
 }

 int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
 {
 	if (list_empty(&res->granted) &&
 	    list_empty(&res->converting) &&
 	    list_empty(&res->blocked))
 		return 0;
 	return 1;
 }

 /* "unused": the lockres has no locks, is not on the dirty list,
  * has no inflight locks (in the gap between mastery and acquiring
  * the first lock), and has no bits in its refmap.
  * truly ready to be freed. */
 int __dlm_lockres_unused(struct dlm_lock_resource *res)
 {
 	int bit;

 	assert_spin_locked(&res->spinlock);

 	if (__dlm_lockres_has_locks(res))
 		return 0;

 	/* Locks are in the process of being created */
 	if (res->inflight_locks)
 		return 0;

 	if (!list_empty(&res->dirty) || res->state & DLM_LOCK_RES_DIRTY)
 		return 0;

 	if (res->state & DLM_LOCK_RES_RECOVERING)
 		return 0;

 	/* Another node has this resource with this node as the master */
 	bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
 	if (bit < O2NM_MAX_NODES)
 		return 0;

 	return 1;
 }


 /* Call whenever you may have added or deleted something from one of
  * the lockres queue's. This will figure out whether it belongs on the
  * unused list or not and does the appropriate thing. */
 void __dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
 			      struct dlm_lock_resource *res)
 {
 	assert_spin_locked(&dlm->spinlock);
 	assert_spin_locked(&res->spinlock);

 	if (__dlm_lockres_unused(res)){
 		if (list_empty(&res->purge)) {
 			mlog(0, "%s: Adding res %.*s to purge list\n",
 			     dlm->name, res->lockname.len, res->lockname.name);

 			res->last_used = jiffies;
 			dlm_lockres_get(res);
 			list_add_tail(&res->purge, &dlm->purge_list);
 			dlm->purge_count++;
 		}
 	} else if (!list_empty(&res->purge)) {
 		mlog(0, "%s: Removing res %.*s from purge list\n",
 		     dlm->name, res->lockname.len, res->lockname.name);

 		list_del_init(&res->purge);
 		dlm_lockres_put(res);
 		dlm->purge_count--;
 	}
 }

 void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
 			    struct dlm_lock_resource *res)
 {
 	spin_lock(&dlm->spinlock);
 	spin_lock(&res->spinlock);

 	__dlm_lockres_calc_usage(dlm, res);

 	spin_unlock(&res->spinlock);
 	spin_unlock(&dlm->spinlock);
 }

 static void dlm_purge_lockres(struct dlm_ctxt *dlm,
 			     struct dlm_lock_resource *res)
 {
 	int master;
 	int ret = 0;

 	assert_spin_locked(&dlm->spinlock);
 	assert_spin_locked(&res->spinlock);

 	master = (res->owner == dlm->node_num);

 	mlog(0, "%s: Purging res %.*s, master %d\n", dlm->name,
 	     res->lockname.len, res->lockname.name, master);

 	if (!master) {
 		res->state |= DLM_LOCK_RES_DROPPING_REF;
 		/* drop spinlock...  retake below */
 		spin_unlock(&res->spinlock);
 		spin_unlock(&dlm->spinlock);

 		spin_lock(&res->spinlock);
 		/* This ensures that clear refmap is sent after the set */
 		__dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_SETREF_INPROG);
 		spin_unlock(&res->spinlock);

 		/* clear our bit from the master's refmap, ignore errors */
 		ret = dlm_drop_lockres_ref(dlm, res);
 		if (ret < 0) {
 			if (!dlm_is_host_down(ret))
 				BUG();
 		}
 		spin_lock(&dlm->spinlock);
 		spin_lock(&res->spinlock);
 	}

 	if (!list_empty(&res->purge)) {
 		mlog(0, "%s: Removing res %.*s from purgelist, master %d\n",
 		     dlm->name, res->lockname.len, res->lockname.name, master);
 		list_del_init(&res->purge);
 		dlm_lockres_put(res);
 		dlm->purge_count--;
 	}

 	if (!__dlm_lockres_unused(res)) {
 		mlog(ML_ERROR, "%s: res %.*s in use after deref\n",
 		     dlm->name, res->lockname.len, res->lockname.name);
 		__dlm_print_one_lock_resource(res);
 		BUG();
 	}

 	__dlm_unhash_lockres(dlm, res);

 	spin_lock(&dlm->track_lock);
 	if (!list_empty(&res->tracking))
 		list_del_init(&res->tracking);
 	else {
 		mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",
 				res->lockname.len, res->lockname.name);
 		__dlm_print_one_lock_resource(res);
 	}
 	spin_unlock(&dlm->track_lock);

 	/* lockres is not in the hash now.  drop the flag and wake up
 	 * any processes waiting in dlm_get_lock_resource. */
 	if (!master) {
 		res->state &= ~DLM_LOCK_RES_DROPPING_REF;
 		spin_unlock(&res->spinlock);
 		wake_up(&res->wq);
 	} else
 		spin_unlock(&res->spinlock);
 }

 static void dlm_run_purge_list(struct dlm_ctxt *dlm,
 			       int purge_now)
 {
 	unsigned int run_max, unused;
 	unsigned long purge_jiffies;
 	struct dlm_lock_resource *lockres;

 	spin_lock(&dlm->spinlock);
 	run_max = dlm->purge_count;

 	while(run_max && !list_empty(&dlm->purge_list)) {
 		run_max--;

 		lockres = list_entry(dlm->purge_list.next,
 				     struct dlm_lock_resource, purge);

 		spin_lock(&lockres->spinlock);

 		purge_jiffies = lockres->last_used +
 			msecs_to_jiffies(DLM_PURGE_INTERVAL_MS);

 		/* Make sure that we want to be processing this guy at
 		 * this time. */
 		if (!purge_now && time_after(purge_jiffies, jiffies)) {
 			/* Since resources are added to the purge list
 			 * in tail order, we can stop at the first
 			 * unpurgable resource -- anyone added after
 			 * him will have a greater last_used value */
 			spin_unlock(&lockres->spinlock);
 			break;
 		}

 		/* Status of the lockres *might* change so double
 		 * check. If the lockres is unused, holding the dlm
 		 * spinlock will prevent people from getting and more
 		 * refs on it. */
 		unused = __dlm_lockres_unused(lockres);
 		if (!unused ||
 		    (lockres->state & DLM_LOCK_RES_MIGRATING) ||
 		    (lockres->inflight_assert_workers != 0)) {
 			mlog(0, "%s: res %.*s is in use or being remastered, "
 			     "used %d, state %d, assert master workers %u\n",
 			     dlm->name, lockres->lockname.len,
 			     lockres->lockname.name,
 			     !unused, lockres->state,
 			     lockres->inflight_assert_workers);
 			list_move_tail(&lockres->purge, &dlm->purge_list);
 			spin_unlock(&lockres->spinlock);
 			continue;
 		}

 		dlm_lockres_get(lockres);

 		dlm_purge_lockres(dlm, lockres);

 		dlm_lockres_put(lockres);

 		/* Avoid adding any scheduling latencies */
 		cond_resched_lock(&dlm->spinlock);
 	}

 	spin_unlock(&dlm->spinlock);
 }

 static void dlm_shuffle_lists(struct dlm_ctxt *dlm,
 			      struct dlm_lock_resource *res)
 {
 	struct dlm_lock *lock, *target;
 	int can_grant = 1;

 	/*
 	 * Because this function is called with the lockres
 	 * spinlock, and because we know that it is not migrating/
 	 * recovering/in-progress, it is fine to reserve asts and
 	 * basts right before queueing them all throughout
 	 */
 	assert_spin_locked(&dlm->ast_lock);
 	assert_spin_locked(&res->spinlock);
 	BUG_ON((res->state & (DLM_LOCK_RES_MIGRATING|
 			      DLM_LOCK_RES_RECOVERING|
 			      DLM_LOCK_RES_IN_PROGRESS)));

 converting:
 	if (list_empty(&res->converting))
 		goto blocked;
 	mlog(0, "%s: res %.*s has locks on the convert queue\n", dlm->name,
 	     res->lockname.len, res->lockname.name);

 	target = list_entry(res->converting.next, struct dlm_lock, list);
 	if (target->ml.convert_type == LKM_IVMODE) {
 		mlog(ML_ERROR, "%s: res %.*s converting lock to invalid mode\n",
 		     dlm->name, res->lockname.len, res->lockname.name);
 		BUG();
 	}
 	list_for_each_entry(lock, &res->granted, list) {
 		if (lock==target)
 			continue;
 		if (!dlm_lock_compatible(lock->ml.type,
 					 target->ml.convert_type)) {
 			can_grant = 0;
 			/* queue the BAST if not already */
 			if (lock->ml.highest_blocked == LKM_IVMODE) {
 				__dlm_lockres_reserve_ast(res);
 				__dlm_queue_bast(dlm, lock);
 			}
 			/* update the highest_blocked if needed */
 			if (lock->ml.highest_blocked < target->ml.convert_type)
 				lock->ml.highest_blocked =
 					target->ml.convert_type;
 		}
 	}

 	list_for_each_entry(lock, &res->converting, list) {
 		if (lock==target)
 			continue;
 		if (!dlm_lock_compatible(lock->ml.type,
 					 target->ml.convert_type)) {
 			can_grant = 0;
 			if (lock->ml.highest_blocked == LKM_IVMODE) {
 				__dlm_lockres_reserve_ast(res);
 				__dlm_queue_bast(dlm, lock);
 			}
 			if (lock->ml.highest_blocked < target->ml.convert_type)
 				lock->ml.highest_blocked =
 					target->ml.convert_type;
 		}
 	}

 	/* we can convert the lock */
 	if (can_grant) {
 		spin_lock(&target->spinlock);
 		BUG_ON(target->ml.highest_blocked != LKM_IVMODE);

 		mlog(0, "%s: res %.*s, AST for Converting lock %u:%llu, type "
 		     "%d => %d, node %u\n", dlm->name, res->lockname.len,
 		     res->lockname.name,
 		     dlm_get_lock_cookie_node(be64_to_cpu(target->ml.cookie)),
 		     dlm_get_lock_cookie_seq(be64_to_cpu(target->ml.cookie)),
 		     target->ml.type,
 		     target->ml.convert_type, target->ml.node);

 		target->ml.type = target->ml.convert_type;
 		target->ml.convert_type = LKM_IVMODE;
 		list_move_tail(&target->list, &res->granted);

 		BUG_ON(!target->lksb);
 		target->lksb->status = DLM_NORMAL;

 		spin_unlock(&target->spinlock);

 		__dlm_lockres_reserve_ast(res);
 		__dlm_queue_ast(dlm, target);
 		/* go back and check for more */
 		goto converting;
 	}

 blocked:
 	if (list_empty(&res->blocked))
 		goto leave;
 	target = list_entry(res->blocked.next, struct dlm_lock, list);

 	list_for_each_entry(lock, &res->granted, list) {
 		if (lock==target)
 			continue;
 		if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
 			can_grant = 0;
 			if (lock->ml.highest_blocked == LKM_IVMODE) {
 				__dlm_lockres_reserve_ast(res);
 				__dlm_queue_bast(dlm, lock);
 			}
 			if (lock->ml.highest_blocked < target->ml.type)
 				lock->ml.highest_blocked = target->ml.type;
 		}
 	}

 	list_for_each_entry(lock, &res->converting, list) {
 		if (lock==target)
 			continue;
 		if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
 			can_grant = 0;
 			if (lock->ml.highest_blocked == LKM_IVMODE) {
 				__dlm_lockres_reserve_ast(res);
 				__dlm_queue_bast(dlm, lock);
 			}
 			if (lock->ml.highest_blocked < target->ml.type)
 				lock->ml.highest_blocked = target->ml.type;
 		}
 	}

 	/* we can grant the blocked lock (only
 	 * possible if converting list empty) */
 	if (can_grant) {
 		spin_lock(&target->spinlock);
 		BUG_ON(target->ml.highest_blocked != LKM_IVMODE);

 		mlog(0, "%s: res %.*s, AST for Blocked lock %u:%llu, type %d, "
 		     "node %u\n", dlm->name, res->lockname.len,
 		     res->lockname.name,
 		     dlm_get_lock_cookie_node(be64_to_cpu(target->ml.cookie)),
 		     dlm_get_lock_cookie_seq(be64_to_cpu(target->ml.cookie)),
 		     target->ml.type, target->ml.node);

 		/* target->ml.type is already correct */
 		list_move_tail(&target->list, &res->granted);

 		BUG_ON(!target->lksb);
 		target->lksb->status = DLM_NORMAL;

 		spin_unlock(&target->spinlock);

 		__dlm_lockres_reserve_ast(res);
 		__dlm_queue_ast(dlm, target);
 		/* go back and check for more */
 		goto converting;
 	}

 leave:
 	return;
 }

 /* must have NO locks when calling this with res !=NULL * */
 void dlm_kick_thread(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 {
 	if (res) {
 		spin_lock(&dlm->spinlock);
 		spin_lock(&res->spinlock);
 		__dlm_dirty_lockres(dlm, res);
 		spin_unlock(&res->spinlock);
 		spin_unlock(&dlm->spinlock);
 	}
 	wake_up(&dlm->dlm_thread_wq);
 }

 void __dlm_dirty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 {
 	assert_spin_locked(&dlm->spinlock);
 	assert_spin_locked(&res->spinlock);

 	/* don't shuffle secondary queues */
 	if ((res->owner == dlm->node_num)) {
 		if (res->state & (DLM_LOCK_RES_MIGRATING |
 				  DLM_LOCK_RES_BLOCK_DIRTY))
 		    return;

 		if (list_empty(&res->dirty)) {
 			/* ref for dirty_list */
 			dlm_lockres_get(res);
 			list_add_tail(&res->dirty, &dlm->dirty_list);
 			res->state |= DLM_LOCK_RES_DIRTY;
 		}
 	}

 	mlog(0, "%s: res %.*s\n", dlm->name, res->lockname.len,
 	     res->lockname.name);
 }


 /* Launch the NM thread for the mounted volume */
 int dlm_launch_thread(struct dlm_ctxt *dlm)
 {
 	mlog(0, "Starting dlm_thread...\n");

 	dlm->dlm_thread_task = kthread_run(dlm_thread, dlm, "dlm_thread");
 	if (IS_ERR(dlm->dlm_thread_task)) {
 		mlog_errno(PTR_ERR(dlm->dlm_thread_task));
 		dlm->dlm_thread_task = NULL;
 		return -EINVAL;
 	}

 	return 0;
 }

 void dlm_complete_thread(struct dlm_ctxt *dlm)
 {
 	if (dlm->dlm_thread_task) {
 		mlog(ML_KTHREAD, "Waiting for dlm thread to exit\n");
 		kthread_stop(dlm->dlm_thread_task);
 		dlm->dlm_thread_task = NULL;
 	}
 }

 static int dlm_dirty_list_empty(struct dlm_ctxt *dlm)
 {
 	int empty;

 	spin_lock(&dlm->spinlock);
 	empty = list_empty(&dlm->dirty_list);
 	spin_unlock(&dlm->spinlock);

 	return empty;
 }

 static void dlm_flush_asts(struct dlm_ctxt *dlm)
 {
 	int ret;
 	struct dlm_lock *lock;
 	struct dlm_lock_resource *res;
 	u8 hi;

 	spin_lock(&dlm->ast_lock);
 	while (!list_empty(&dlm->pending_asts)) {
 		lock = list_entry(dlm->pending_asts.next,
 				  struct dlm_lock, ast_list);
 		/* get an extra ref on lock */
 		dlm_lock_get(lock);
 		res = lock->lockres;
 		mlog(0, "%s: res %.*s, Flush AST for lock %u:%llu, type %d, "
 		     "node %u\n", dlm->name, res->lockname.len,
 		     res->lockname.name,
 		     dlm_get_lock_cookie_node(be64_to_cpu(lock->ml.cookie)),
 		     dlm_get_lock_cookie_seq(be64_to_cpu(lock->ml.cookie)),
 		     lock->ml.type, lock->ml.node);

 		BUG_ON(!lock->ast_pending);

 		/* remove from list (including ref) */
 		list_del_init(&lock->ast_list);
 		dlm_lock_put(lock);
 		spin_unlock(&dlm->ast_lock);

 		if (lock->ml.node != dlm->node_num) {
 			ret = dlm_do_remote_ast(dlm, res, lock);
 			if (ret < 0)
 				mlog_errno(ret);
 		} else
 			dlm_do_local_ast(dlm, res, lock);

 		spin_lock(&dlm->ast_lock);

 		/* possible that another ast was queued while
 		 * we were delivering the last one */
 		if (!list_empty(&lock->ast_list)) {
 			mlog(0, "%s: res %.*s, AST queued while flushing last "
 			     "one\n", dlm->name, res->lockname.len,
 			     res->lockname.name);
 		} else
 			lock->ast_pending = 0;

 		/* drop the extra ref.
 		 * this may drop it completely. */
 		dlm_lock_put(lock);
 		dlm_lockres_release_ast(dlm, res);
 	}

 	while (!list_empty(&dlm->pending_basts)) {
 		lock = list_entry(dlm->pending_basts.next,
 				  struct dlm_lock, bast_list);
 		/* get an extra ref on lock */
 		dlm_lock_get(lock);
 		res = lock->lockres;

 		BUG_ON(!lock->bast_pending);

 		/* get the highest blocked lock, and reset */
 		spin_lock(&lock->spinlock);
 		BUG_ON(lock->ml.highest_blocked <= LKM_IVMODE);
 		hi = lock->ml.highest_blocked;
 		lock->ml.highest_blocked = LKM_IVMODE;
 		spin_unlock(&lock->spinlock);

 		/* remove from list (including ref) */
 		list_del_init(&lock->bast_list);
 		dlm_lock_put(lock);
 		spin_unlock(&dlm->ast_lock);

 		mlog(0, "%s: res %.*s, Flush BAST for lock %u:%llu, "
 		     "blocked %d, node %u\n",
 		     dlm->name, res->lockname.len, res->lockname.name,
 		     dlm_get_lock_cookie_node(be64_to_cpu(lock->ml.cookie)),
 		     dlm_get_lock_cookie_seq(be64_to_cpu(lock->ml.cookie)),
 		     hi, lock->ml.node);

 		if (lock->ml.node != dlm->node_num) {
 			ret = dlm_send_proxy_bast(dlm, res, lock, hi);
 			if (ret < 0)
 				mlog_errno(ret);
 		} else
 			dlm_do_local_bast(dlm, res, lock, hi);

 		spin_lock(&dlm->ast_lock);

 		/* possible that another bast was queued while
 		 * we were delivering the last one */
 		if (!list_empty(&lock->bast_list)) {
 			mlog(0, "%s: res %.*s, BAST queued while flushing last "
 			     "one\n", dlm->name, res->lockname.len,
 			     res->lockname.name);
 		} else
 			lock->bast_pending = 0;

 		/* drop the extra ref.
 		 * this may drop it completely. */
 		dlm_lock_put(lock);
 		dlm_lockres_release_ast(dlm, res);
 	}
 	wake_up(&dlm->ast_wq);
 	spin_unlock(&dlm->ast_lock);
 }


 #define DLM_THREAD_TIMEOUT_MS (4 * 1000)
 #define DLM_THREAD_MAX_DIRTY  100
 #define DLM_THREAD_MAX_ASTS   10

 static int dlm_thread(void *data)
 {
 	struct dlm_lock_resource *res;
 	struct dlm_ctxt *dlm = data;
 	unsigned long timeout = msecs_to_jiffies(DLM_THREAD_TIMEOUT_MS);

 	mlog(0, "dlm thread running for %s...\n", dlm->name);

 	while (!kthread_should_stop()) {
 		int n = DLM_THREAD_MAX_DIRTY;

 		/* dlm_shutting_down is very point-in-time, but that
 		 * doesn't matter as we'll just loop back around if we
 		 * get false on the leading edge of a state
 		 * transition. */
 		dlm_run_purge_list(dlm, dlm_shutting_down(dlm));

 		/* We really don't want to hold dlm->spinlock while
 		 * calling dlm_shuffle_lists on each lockres that
 		 * needs to have its queues adjusted and AST/BASTs
 		 * run.  So let's pull each entry off the dirty_list
 		 * and drop dlm->spinlock ASAP.  Once off the list,
 		 * res->spinlock needs to be taken again to protect
 		 * the queues while calling dlm_shuffle_lists.  */
 		spin_lock(&dlm->spinlock);
 		while (!list_empty(&dlm->dirty_list)) {
 			int delay = 0;
 			res = list_entry(dlm->dirty_list.next,
 					 struct dlm_lock_resource, dirty);

 			/* peel a lockres off, remove it from the list,
 			 * unset the dirty flag and drop the dlm lock */
 			BUG_ON(!res);
 			dlm_lockres_get(res);

 			spin_lock(&res->spinlock);
 			/* We clear the DLM_LOCK_RES_DIRTY state once we shuffle lists below */
 			list_del_init(&res->dirty);
 			spin_unlock(&res->spinlock);
 			spin_unlock(&dlm->spinlock);
 			/* Drop dirty_list ref */
 			dlm_lockres_put(res);

 		 	/* lockres can be re-dirtied/re-added to the
 			 * dirty_list in this gap, but that is ok */

 			spin_lock(&dlm->ast_lock);
 			spin_lock(&res->spinlock);
 			if (res->owner != dlm->node_num) {
 				__dlm_print_one_lock_resource(res);
 				mlog(ML_ERROR, "%s: inprog %d, mig %d, reco %d,"
 				     " dirty %d\n", dlm->name,
 				     !!(res->state & DLM_LOCK_RES_IN_PROGRESS),
 				     !!(res->state & DLM_LOCK_RES_MIGRATING),
 				     !!(res->state & DLM_LOCK_RES_RECOVERING),
 				     !!(res->state & DLM_LOCK_RES_DIRTY));
 			}
 			BUG_ON(res->owner != dlm->node_num);

 			/* it is now ok to move lockreses in these states
 			 * to the dirty list, assuming that they will only be
 			 * dirty for a short while. */
 			BUG_ON(res->state & DLM_LOCK_RES_MIGRATING);
 			if (res->state & (DLM_LOCK_RES_IN_PROGRESS |
 					  DLM_LOCK_RES_RECOVERING)) {
 				/* move it to the tail and keep going */
 				res->state &= ~DLM_LOCK_RES_DIRTY;
 				spin_unlock(&res->spinlock);
 				spin_unlock(&dlm->ast_lock);
 				mlog(0, "%s: res %.*s, inprogress, delay list "
 				     "shuffle, state %d\n", dlm->name,
 				     res->lockname.len, res->lockname.name,
 				     res->state);
 				delay = 1;
 				goto in_progress;
 			}

 			/* at this point the lockres is not migrating/
 			 * recovering/in-progress.  we have the lockres
 			 * spinlock and do NOT have the dlm lock.
 			 * safe to reserve/queue asts and run the lists. */

 			/* called while holding lockres lock */
 			dlm_shuffle_lists(dlm, res);
 			res->state &= ~DLM_LOCK_RES_DIRTY;
 			spin_unlock(&res->spinlock);
 			spin_unlock(&dlm->ast_lock);

 			dlm_lockres_calc_usage(dlm, res);

 in_progress:

 			spin_lock(&dlm->spinlock);
 			/* if the lock was in-progress, stick
 			 * it on the back of the list */
 			if (delay) {
 				spin_lock(&res->spinlock);
 				__dlm_dirty_lockres(dlm, res);
 				spin_unlock(&res->spinlock);
 			}
 			dlm_lockres_put(res);

 			/* unlikely, but we may need to give time to
 			 * other tasks */
 			if (!--n) {
 				mlog(0, "%s: Throttling dlm thread\n",
 				     dlm->name);
 				break;
 			}
 		}

 		spin_unlock(&dlm->spinlock);
 		dlm_flush_asts(dlm);

 		/* yield and continue right away if there is more work to do */
 		if (!n) {
 			cond_resched();
 			continue;
 		}

 		wait_event_interruptible_timeout(dlm->dlm_thread_wq,
 						 !dlm_dirty_list_empty(dlm) ||
 						 kthread_should_stop(),
 						 timeout);
 	}

 	mlog(0, "quitting DLM thread\n");
 	return 0;
 }
	/* -- mode: c; c-basic-offset: 8; --
	* vim: noexpandtab sw=8 ts=8 sts=0:
	*
	* dlmthread.c
	*
	* standalone DLM module
	*
	* Copyright (C) 2004 Oracle. All rights reserved.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public
	* License along with this program; if not, write to the
	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	* Boston, MA 021110-1307, USA.
	*
	*/


	#include <linux/module.h>
	#include <linux/fs.h>
	#include <linux/types.h>
	#include <linux/highmem.h>
	#include <linux/init.h>
	#include <linux/sysctl.h>
	#include <linux/random.h>
	#include <linux/blkdev.h>
	#include <linux/socket.h>
	#include <linux/inet.h>
	#include <linux/timer.h>
	#include <linux/kthread.h>
	#include <linux/delay.h>


	#include "cluster/heartbeat.h"
	#include "cluster/nodemanager.h"
	#include "cluster/tcp.h"

	#include "dlmapi.h"
	#include "dlmcommon.h"
	#include "dlmdomain.h"

	#define MLOG_MASK_PREFIX (ML_DLM\|ML_DLM_THREAD)
	#include "cluster/masklog.h"

	static int dlm_thread(void *data);
	static void dlm_flush_asts(struct dlm_ctxt *dlm);

	#define dlm_lock_is_remote(dlm, lock) ((lock)->ml.node != (dlm)->node_num)

	/* will exit holding res->spinlock, but may drop in function */
	/* waits until flags are cleared on res->state */
	void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags)
	{
	DECLARE_WAITQUEUE(wait, current);

	assert_spin_locked(&res->spinlock);

	add_wait_queue(&res->wq, &wait);
	repeat:
	set_current_state(TASK_UNINTERRUPTIBLE);
	if (res->state & flags) {
	spin_unlock(&res->spinlock);
	schedule();
	spin_lock(&res->spinlock);
	goto repeat;
	}
	remove_wait_queue(&res->wq, &wait);
	__set_current_state(TASK_RUNNING);
	}

	int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
	{
	if (list_empty(&res->granted) &&
	list_empty(&res->converting) &&
	list_empty(&res->blocked))
	return 0;
	return 1;
	}

	/* "unused": the lockres has no locks, is not on the dirty list,
	* has no inflight locks (in the gap between mastery and acquiring
	* the first lock), and has no bits in its refmap.
	* truly ready to be freed. */
	int __dlm_lockres_unused(struct dlm_lock_resource *res)
	{
	int bit;

	assert_spin_locked(&res->spinlock);

	if (__dlm_lockres_has_locks(res))
	return 0;

	/* Locks are in the process of being created */
	if (res->inflight_locks)
	return 0;

	if (!list_empty(&res->dirty) \|\| res->state & DLM_LOCK_RES_DIRTY)
	return 0;

	if (res->state & DLM_LOCK_RES_RECOVERING)
	return 0;

	/* Another node has this resource with this node as the master */
	bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
	if (bit < O2NM_MAX_NODES)
	return 0;

	return 1;
	}


	/* Call whenever you may have added or deleted something from one of
	* the lockres queue's. This will figure out whether it belongs on the
	* unused list or not and does the appropriate thing. */
	void __dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
	struct dlm_lock_resource *res)
	{
	assert_spin_locked(&dlm->spinlock);
	assert_spin_locked(&res->spinlock);

	if (__dlm_lockres_unused(res)){
	if (list_empty(&res->purge)) {
	mlog(0, "%s: Adding res %.*s to purge list\n",
	dlm->name, res->lockname.len, res->lockname.name);

	res->last_used = jiffies;
	dlm_lockres_get(res);
	list_add_tail(&res->purge, &dlm->purge_list);
	dlm->purge_count++;
	}
	} else if (!list_empty(&res->purge)) {
	mlog(0, "%s: Removing res %.*s from purge list\n",
	dlm->name, res->lockname.len, res->lockname.name);

	list_del_init(&res->purge);
	dlm_lockres_put(res);
	dlm->purge_count--;
	}
	}

	void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
	struct dlm_lock_resource *res)
	{
	spin_lock(&dlm->spinlock);
	spin_lock(&res->spinlock);

	__dlm_lockres_calc_usage(dlm, res);

	spin_unlock(&res->spinlock);
	spin_unlock(&dlm->spinlock);
	}

	static void dlm_purge_lockres(struct dlm_ctxt *dlm,
	struct dlm_lock_resource *res)
	{
	int master;
	int ret = 0;

	assert_spin_locked(&dlm->spinlock);
	assert_spin_locked(&res->spinlock);

	master = (res->owner == dlm->node_num);

	mlog(0, "%s: Purging res %.*s, master %d\n", dlm->name,
	res->lockname.len, res->lockname.name, master);

	if (!master) {
	res->state \|= DLM_LOCK_RES_DROPPING_REF;
	/* drop spinlock... retake below */
	spin_unlock(&res->spinlock);
	spin_unlock(&dlm->spinlock);

	spin_lock(&res->spinlock);
	/* This ensures that clear refmap is sent after the set */
	__dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_SETREF_INPROG);
	spin_unlock(&res->spinlock);

	/* clear our bit from the master's refmap, ignore errors */
	ret = dlm_drop_lockres_ref(dlm, res);
	if (ret < 0) {
	if (!dlm_is_host_down(ret))
	BUG();
	}
	spin_lock(&dlm->spinlock);
	spin_lock(&res->spinlock);
	}

	if (!list_empty(&res->purge)) {
	mlog(0, "%s: Removing res %.*s from purgelist, master %d\n",
	dlm->name, res->lockname.len, res->lockname.name, master);
	list_del_init(&res->purge);
	dlm_lockres_put(res);
	dlm->purge_count--;
	}

	if (!__dlm_lockres_unused(res)) {
	mlog(ML_ERROR, "%s: res %.*s in use after deref\n",
	dlm->name, res->lockname.len, res->lockname.name);
	__dlm_print_one_lock_resource(res);
	BUG();
	}

	__dlm_unhash_lockres(dlm, res);

	spin_lock(&dlm->track_lock);
	if (!list_empty(&res->tracking))
	list_del_init(&res->tracking);
	else {
	mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",
	res->lockname.len, res->lockname.name);
	__dlm_print_one_lock_resource(res);
	}
	spin_unlock(&dlm->track_lock);

	/* lockres is not in the hash now. drop the flag and wake up
	* any processes waiting in dlm_get_lock_resource. */
	if (!master) {
	res->state &= ~DLM_LOCK_RES_DROPPING_REF;
	spin_unlock(&res->spinlock);
	wake_up(&res->wq);
	} else
	spin_unlock(&res->spinlock);
	}

	static void dlm_run_purge_list(struct dlm_ctxt *dlm,
	int purge_now)
	{
	unsigned int run_max, unused;
	unsigned long purge_jiffies;
	struct dlm_lock_resource *lockres;

	spin_lock(&dlm->spinlock);
	run_max = dlm->purge_count;

	while(run_max && !list_empty(&dlm->purge_list)) {
	run_max--;

	lockres = list_entry(dlm->purge_list.next,
	struct dlm_lock_resource, purge);

	spin_lock(&lockres->spinlock);

	purge_jiffies = lockres->last_used +
	msecs_to_jiffies(DLM_PURGE_INTERVAL_MS);

	/* Make sure that we want to be processing this guy at
	* this time. */
	if (!purge_now && time_after(purge_jiffies, jiffies)) {
	/* Since resources are added to the purge list
	* in tail order, we can stop at the first
	* unpurgable resource -- anyone added after
	* him will have a greater last_used value */
	spin_unlock(&lockres->spinlock);
	break;
	}

	/* Status of the lockres might change so double
	* check. If the lockres is unused, holding the dlm
	* spinlock will prevent people from getting and more
	* refs on it. */
	unused = __dlm_lockres_unused(lockres);
	if (!unused \|\|
	(lockres->state & DLM_LOCK_RES_MIGRATING) \|\|
	(lockres->inflight_assert_workers != 0)) {
	mlog(0, "%s: res %.*s is in use or being remastered, "
	"used %d, state %d, assert master workers %u\n",
	dlm->name, lockres->lockname.len,
	lockres->lockname.name,
	!unused, lockres->state,
	lockres->inflight_assert_workers);
	list_move_tail(&lockres->purge, &dlm->purge_list);
	spin_unlock(&lockres->spinlock);
	continue;
	}

	dlm_lockres_get(lockres);

	dlm_purge_lockres(dlm, lockres);

	dlm_lockres_put(lockres);

	/* Avoid adding any scheduling latencies */
	cond_resched_lock(&dlm->spinlock);
	}

	spin_unlock(&dlm->spinlock);
	}

	static void dlm_shuffle_lists(struct dlm_ctxt *dlm,
	struct dlm_lock_resource *res)
	{
	struct dlm_lock lock, target;
	int can_grant = 1;

	/*
	* Because this function is called with the lockres
	* spinlock, and because we know that it is not migrating/
	* recovering/in-progress, it is fine to reserve asts and
	* basts right before queueing them all throughout
	*/
	assert_spin_locked(&dlm->ast_lock);
	assert_spin_locked(&res->spinlock);
	BUG_ON((res->state & (DLM_LOCK_RES_MIGRATING\|
	DLM_LOCK_RES_RECOVERING\|
	DLM_LOCK_RES_IN_PROGRESS)));

	converting:
	if (list_empty(&res->converting))
	goto blocked;
	mlog(0, "%s: res %.*s has locks on the convert queue\n", dlm->name,
	res->lockname.len, res->lockname.name);

	target = list_entry(res->converting.next, struct dlm_lock, list);
	if (target->ml.convert_type == LKM_IVMODE) {
	mlog(ML_ERROR, "%s: res %.*s converting lock to invalid mode\n",
	dlm->name, res->lockname.len, res->lockname.name);
	BUG();
	}
	list_for_each_entry(lock, &res->granted, list) {
	if (lock==target)
	continue;
	if (!dlm_lock_compatible(lock->ml.type,
	target->ml.convert_type)) {
	can_grant = 0;
	/* queue the BAST if not already */
	if (lock->ml.highest_blocked == LKM_IVMODE) {
	__dlm_lockres_reserve_ast(res);
	__dlm_queue_bast(dlm, lock);
	}
	/* update the highest_blocked if needed */
	if (lock->ml.highest_blocked < target->ml.convert_type)
	lock->ml.highest_blocked =
	target->ml.convert_type;
	}
	}

	list_for_each_entry(lock, &res->converting, list) {
	if (lock==target)
	continue;
	if (!dlm_lock_compatible(lock->ml.type,
	target->ml.convert_type)) {
	can_grant = 0;
	if (lock->ml.highest_blocked == LKM_IVMODE) {
	__dlm_lockres_reserve_ast(res);
	__dlm_queue_bast(dlm, lock);
	}
	if (lock->ml.highest_blocked < target->ml.convert_type)
	lock->ml.highest_blocked =
	target->ml.convert_type;
	}
	}

	/* we can convert the lock */
	if (can_grant) {
	spin_lock(&target->spinlock);
	BUG_ON(target->ml.highest_blocked != LKM_IVMODE);

	mlog(0, "%s: res %.*s, AST for Converting lock %u:%llu, type "
	"%d => %d, node %u\n", dlm->name, res->lockname.len,
	res->lockname.name,
	dlm_get_lock_cookie_node(be64_to_cpu(target->ml.cookie)),
	dlm_get_lock_cookie_seq(be64_to_cpu(target->ml.cookie)),
	target->ml.type,
	target->ml.convert_type, target->ml.node);

	target->ml.type = target->ml.convert_type;
	target->ml.convert_type = LKM_IVMODE;
	list_move_tail(&target->list, &res->granted);

	BUG_ON(!target->lksb);
	target->lksb->status = DLM_NORMAL;

	spin_unlock(&target->spinlock);

	__dlm_lockres_reserve_ast(res);
	__dlm_queue_ast(dlm, target);
	/* go back and check for more */
	goto converting;
	}

	blocked:
	if (list_empty(&res->blocked))
	goto leave;
	target = list_entry(res->blocked.next, struct dlm_lock, list);

	list_for_each_entry(lock, &res->granted, list) {
	if (lock==target)
	continue;
	if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
	can_grant = 0;
	if (lock->ml.highest_blocked == LKM_IVMODE) {
	__dlm_lockres_reserve_ast(res);
	__dlm_queue_bast(dlm, lock);
	}
	if (lock->ml.highest_blocked < target->ml.type)
	lock->ml.highest_blocked = target->ml.type;
	}
	}

	list_for_each_entry(lock, &res->converting, list) {
	if (lock==target)
	continue;
	if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
	can_grant = 0;
	if (lock->ml.highest_blocked == LKM_IVMODE) {
	__dlm_lockres_reserve_ast(res);
	__dlm_queue_bast(dlm, lock);
	}
	if (lock->ml.highest_blocked < target->ml.type)
	lock->ml.highest_blocked = target->ml.type;
	}
	}

	/* we can grant the blocked lock (only
	* possible if converting list empty) */
	if (can_grant) {
	spin_lock(&target->spinlock);
	BUG_ON(target->ml.highest_blocked != LKM_IVMODE);

	mlog(0, "%s: res %.*s, AST for Blocked lock %u:%llu, type %d, "
	"node %u\n", dlm->name, res->lockname.len,
	res->lockname.name,
	dlm_get_lock_cookie_node(be64_to_cpu(target->ml.cookie)),
	dlm_get_lock_cookie_seq(be64_to_cpu(target->ml.cookie)),
	target->ml.type, target->ml.node);

	/* target->ml.type is already correct */
	list_move_tail(&target->list, &res->granted);

	BUG_ON(!target->lksb);
	target->lksb->status = DLM_NORMAL;

	spin_unlock(&target->spinlock);

	__dlm_lockres_reserve_ast(res);
	__dlm_queue_ast(dlm, target);
	/* go back and check for more */
	goto converting;
	}

	leave:
	return;
	}

	/* must have NO locks when calling this with res !=NULL * */
	void dlm_kick_thread(struct dlm_ctxt dlm, struct dlm_lock_resource res)
	{
	if (res) {
	spin_lock(&dlm->spinlock);
	spin_lock(&res->spinlock);
	__dlm_dirty_lockres(dlm, res);
	spin_unlock(&res->spinlock);
	spin_unlock(&dlm->spinlock);
	}
	wake_up(&dlm->dlm_thread_wq);
	}

	void __dlm_dirty_lockres(struct dlm_ctxt dlm, struct dlm_lock_resource res)
	{
	assert_spin_locked(&dlm->spinlock);
	assert_spin_locked(&res->spinlock);

	/* don't shuffle secondary queues */
	if ((res->owner == dlm->node_num)) {
	if (res->state & (DLM_LOCK_RES_MIGRATING \|
	DLM_LOCK_RES_BLOCK_DIRTY))
	return;

	if (list_empty(&res->dirty)) {
	/* ref for dirty_list */
	dlm_lockres_get(res);
	list_add_tail(&res->dirty, &dlm->dirty_list);
	res->state \|= DLM_LOCK_RES_DIRTY;
	}
	}

	mlog(0, "%s: res %.*s\n", dlm->name, res->lockname.len,
	res->lockname.name);
	}


	/* Launch the NM thread for the mounted volume */
	int dlm_launch_thread(struct dlm_ctxt *dlm)
	{
	mlog(0, "Starting dlm_thread...\n");

	dlm->dlm_thread_task = kthread_run(dlm_thread, dlm, "dlm_thread");
	if (IS_ERR(dlm->dlm_thread_task)) {
	mlog_errno(PTR_ERR(dlm->dlm_thread_task));
	dlm->dlm_thread_task = NULL;
	return -EINVAL;
	}

	return 0;
	}

	void dlm_complete_thread(struct dlm_ctxt *dlm)
	{
	if (dlm->dlm_thread_task) {
	mlog(ML_KTHREAD, "Waiting for dlm thread to exit\n");
	kthread_stop(dlm->dlm_thread_task);
	dlm->dlm_thread_task = NULL;
	}
	}

	static int dlm_dirty_list_empty(struct dlm_ctxt *dlm)
	{
	int empty;

	spin_lock(&dlm->spinlock);
	empty = list_empty(&dlm->dirty_list);
	spin_unlock(&dlm->spinlock);

	return empty;
	}

	static void dlm_flush_asts(struct dlm_ctxt *dlm)
	{
	int ret;
	struct dlm_lock *lock;
	struct dlm_lock_resource *res;
	u8 hi;

	spin_lock(&dlm->ast_lock);
	while (!list_empty(&dlm->pending_asts)) {
	lock = list_entry(dlm->pending_asts.next,
	struct dlm_lock, ast_list);
	/* get an extra ref on lock */
	dlm_lock_get(lock);
	res = lock->lockres;
	mlog(0, "%s: res %.*s, Flush AST for lock %u:%llu, type %d, "
	"node %u\n", dlm->name, res->lockname.len,
	res->lockname.name,
	dlm_get_lock_cookie_node(be64_to_cpu(lock->ml.cookie)),
	dlm_get_lock_cookie_seq(be64_to_cpu(lock->ml.cookie)),
	lock->ml.type, lock->ml.node);

	BUG_ON(!lock->ast_pending);

	/* remove from list (including ref) */
	list_del_init(&lock->ast_list);
	dlm_lock_put(lock);
	spin_unlock(&dlm->ast_lock);

	if (lock->ml.node != dlm->node_num) {
	ret = dlm_do_remote_ast(dlm, res, lock);
	if (ret < 0)
	mlog_errno(ret);
	} else
	dlm_do_local_ast(dlm, res, lock);

	spin_lock(&dlm->ast_lock);

	/* possible that another ast was queued while
	* we were delivering the last one */
	if (!list_empty(&lock->ast_list)) {
	mlog(0, "%s: res %.*s, AST queued while flushing last "
	"one\n", dlm->name, res->lockname.len,
	res->lockname.name);
	} else
	lock->ast_pending = 0;

	/* drop the extra ref.
	* this may drop it completely. */
	dlm_lock_put(lock);
	dlm_lockres_release_ast(dlm, res);
	}

	while (!list_empty(&dlm->pending_basts)) {
	lock = list_entry(dlm->pending_basts.next,
	struct dlm_lock, bast_list);
	/* get an extra ref on lock */
	dlm_lock_get(lock);
	res = lock->lockres;

	BUG_ON(!lock->bast_pending);

	/* get the highest blocked lock, and reset */
	spin_lock(&lock->spinlock);
	BUG_ON(lock->ml.highest_blocked <= LKM_IVMODE);
	hi = lock->ml.highest_blocked;
	lock->ml.highest_blocked = LKM_IVMODE;
	spin_unlock(&lock->spinlock);

	/* remove from list (including ref) */
	list_del_init(&lock->bast_list);
	dlm_lock_put(lock);
	spin_unlock(&dlm->ast_lock);

	mlog(0, "%s: res %.*s, Flush BAST for lock %u:%llu, "
	"blocked %d, node %u\n",
	dlm->name, res->lockname.len, res->lockname.name,
	dlm_get_lock_cookie_node(be64_to_cpu(lock->ml.cookie)),
	dlm_get_lock_cookie_seq(be64_to_cpu(lock->ml.cookie)),
	hi, lock->ml.node);

	if (lock->ml.node != dlm->node_num) {
	ret = dlm_send_proxy_bast(dlm, res, lock, hi);
	if (ret < 0)
	mlog_errno(ret);
	} else
	dlm_do_local_bast(dlm, res, lock, hi);

	spin_lock(&dlm->ast_lock);

	/* possible that another bast was queued while
	* we were delivering the last one */
	if (!list_empty(&lock->bast_list)) {
	mlog(0, "%s: res %.*s, BAST queued while flushing last "
	"one\n", dlm->name, res->lockname.len,
	res->lockname.name);
	} else
	lock->bast_pending = 0;

	/* drop the extra ref.
	* this may drop it completely. */
	dlm_lock_put(lock);
	dlm_lockres_release_ast(dlm, res);
	}
	wake_up(&dlm->ast_wq);
	spin_unlock(&dlm->ast_lock);
	}


	#define DLM_THREAD_TIMEOUT_MS (4 * 1000)
	#define DLM_THREAD_MAX_DIRTY 100
	#define DLM_THREAD_MAX_ASTS 10

	static int dlm_thread(void *data)
	{
	struct dlm_lock_resource *res;
	struct dlm_ctxt *dlm = data;
	unsigned long timeout = msecs_to_jiffies(DLM_THREAD_TIMEOUT_MS);

	mlog(0, "dlm thread running for %s...\n", dlm->name);

	while (!kthread_should_stop()) {
	int n = DLM_THREAD_MAX_DIRTY;

	/* dlm_shutting_down is very point-in-time, but that
	* doesn't matter as we'll just loop back around if we
	* get false on the leading edge of a state
	* transition. */
	dlm_run_purge_list(dlm, dlm_shutting_down(dlm));

	/* We really don't want to hold dlm->spinlock while
	* calling dlm_shuffle_lists on each lockres that
	* needs to have its queues adjusted and AST/BASTs
	* run. So let's pull each entry off the dirty_list
	* and drop dlm->spinlock ASAP. Once off the list,
	* res->spinlock needs to be taken again to protect
	* the queues while calling dlm_shuffle_lists. */
	spin_lock(&dlm->spinlock);
	while (!list_empty(&dlm->dirty_list)) {
	int delay = 0;
	res = list_entry(dlm->dirty_list.next,
	struct dlm_lock_resource, dirty);

	/* peel a lockres off, remove it from the list,
	* unset the dirty flag and drop the dlm lock */
	BUG_ON(!res);
	dlm_lockres_get(res);

	spin_lock(&res->spinlock);
	/* We clear the DLM_LOCK_RES_DIRTY state once we shuffle lists below */
	list_del_init(&res->dirty);
	spin_unlock(&res->spinlock);
	spin_unlock(&dlm->spinlock);
	/* Drop dirty_list ref */
	dlm_lockres_put(res);

	/* lockres can be re-dirtied/re-added to the
	* dirty_list in this gap, but that is ok */

	spin_lock(&dlm->ast_lock);
	spin_lock(&res->spinlock);
	if (res->owner != dlm->node_num) {
	__dlm_print_one_lock_resource(res);
	mlog(ML_ERROR, "%s: inprog %d, mig %d, reco %d,"
	" dirty %d\n", dlm->name,
	!!(res->state & DLM_LOCK_RES_IN_PROGRESS),
	!!(res->state & DLM_LOCK_RES_MIGRATING),
	!!(res->state & DLM_LOCK_RES_RECOVERING),
	!!(res->state & DLM_LOCK_RES_DIRTY));
	}
	BUG_ON(res->owner != dlm->node_num);

	/* it is now ok to move lockreses in these states
	* to the dirty list, assuming that they will only be
	* dirty for a short while. */
	BUG_ON(res->state & DLM_LOCK_RES_MIGRATING);
	if (res->state & (DLM_LOCK_RES_IN_PROGRESS \|
	DLM_LOCK_RES_RECOVERING)) {
	/* move it to the tail and keep going */
	res->state &= ~DLM_LOCK_RES_DIRTY;
	spin_unlock(&res->spinlock);
	spin_unlock(&dlm->ast_lock);
	mlog(0, "%s: res %.*s, inprogress, delay list "
	"shuffle, state %d\n", dlm->name,
	res->lockname.len, res->lockname.name,
	res->state);
	delay = 1;
	goto in_progress;
	}

	/* at this point the lockres is not migrating/
	* recovering/in-progress. we have the lockres
	* spinlock and do NOT have the dlm lock.
	* safe to reserve/queue asts and run the lists. */

	/* called while holding lockres lock */
	dlm_shuffle_lists(dlm, res);
	res->state &= ~DLM_LOCK_RES_DIRTY;
	spin_unlock(&res->spinlock);
	spin_unlock(&dlm->ast_lock);

	dlm_lockres_calc_usage(dlm, res);

	in_progress:

	spin_lock(&dlm->spinlock);
	/* if the lock was in-progress, stick
	* it on the back of the list */
	if (delay) {
	spin_lock(&res->spinlock);
	__dlm_dirty_lockres(dlm, res);
	spin_unlock(&res->spinlock);
	}
	dlm_lockres_put(res);

	/* unlikely, but we may need to give time to
	* other tasks */
	if (!--n) {
	mlog(0, "%s: Throttling dlm thread\n",
	dlm->name);
	break;
	}
	}

	spin_unlock(&dlm->spinlock);
	dlm_flush_asts(dlm);

	/* yield and continue right away if there is more work to do */
	if (!n) {
	cond_resched();
	continue;
	}

	wait_event_interruptible_timeout(dlm->dlm_thread_wq,
	!dlm_dirty_list_empty(dlm) \|\|
	kthread_should_stop(),
	timeout);
	}

	mlog(0, "quitting DLM thread\n");
	return 0;
	}