dlmthread.c

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/* -*- 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);

    /* 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)) {
            mlog(0, "%s: res %.*s is in use or being remastered, "
                 "used %d, state %d\n", dlm->name,
                 lockres->lockname.len, lockres->lockname.name,
                 !unused, lockres->state);
            list_move_tail(&dlm->purge_list, &lockres->purge);
            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;
    struct list_head *iter;
    struct list_head *head;
    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();
    }
    head = &res->granted;
    list_for_each(iter, head) {
        lock = list_entry(iter, struct dlm_lock, 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;
        }
    }
    head = &res->converting;
    list_for_each(iter, head) {
        lock = list_entry(iter, struct dlm_lock, 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);

    head = &res->granted;
    list_for_each(iter, head) {
        lock = list_entry(iter, struct dlm_lock, 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;
        }
    }

    head = &res->converting;
    list_for_each(iter, head) {
        lock = list_entry(iter, struct dlm_lock, 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;
}