staging: lustre: remove unused variable

[deliverable/linux.git] / drivers / staging / lustre / lustre / ldlm / ldlm_lockd.c

/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * 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 version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2010, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/ldlm/ldlm_lockd.c
 *
 * Author: Peter Braam <braam@clusterfs.com>
 * Author: Phil Schwan <phil@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_LDLM

#include "../../include/linux/libcfs/libcfs.h"
#include "../include/lustre_dlm.h"
#include "../include/obd_class.h"
#include <linux/list.h>
#include "ldlm_internal.h"

static int ldlm_num_threads;
module_param(ldlm_num_threads, int, 0444);
MODULE_PARM_DESC(ldlm_num_threads, "number of DLM service threads to start");

static char *ldlm_cpts;
module_param(ldlm_cpts, charp, 0444);
MODULE_PARM_DESC(ldlm_cpts, "CPU partitions ldlm threads should run on");

static struct mutex     ldlm_ref_mutex;
static int ldlm_refcount;

static struct kobject *ldlm_kobj;
struct kset *ldlm_ns_kset;
static struct kset *ldlm_svc_kset;

struct ldlm_cb_async_args {
        struct ldlm_cb_set_arg *ca_set_arg;
        struct ldlm_lock       *ca_lock;
};

/* LDLM state */

static struct ldlm_state *ldlm_state;

#define ELT_STOPPED   0
#define ELT_READY     1
#define ELT_TERMINATE 2

struct ldlm_bl_pool {
        spinlock_t              blp_lock;

        /*
         * blp_prio_list is used for callbacks that should be handled
         * as a priority. It is used for LDLM_FL_DISCARD_DATA requests.
         * see bug 13843
         */
        struct list_head              blp_prio_list;

        /*
         * blp_list is used for all other callbacks which are likely
         * to take longer to process.
         */
        struct list_head              blp_list;

        wait_queue_head_t            blp_waitq;
        struct completion       blp_comp;
        atomic_t            blp_num_threads;
        atomic_t            blp_busy_threads;
        int                  blp_min_threads;
        int                  blp_max_threads;
};

struct ldlm_bl_work_item {
        struct list_head              blwi_entry;
        struct ldlm_namespace  *blwi_ns;
        struct ldlm_lock_desc   blwi_ld;
        struct ldlm_lock       *blwi_lock;
        struct list_head              blwi_head;
        int                  blwi_count;
        struct completion       blwi_comp;
        ldlm_cancel_flags_t     blwi_flags;
        int                  blwi_mem_pressure;
};

/**
 * Callback handler for receiving incoming blocking ASTs.
 *
 * This can only happen on client side.
 */
void ldlm_handle_bl_callback(struct ldlm_namespace *ns,
                             struct ldlm_lock_desc *ld, struct ldlm_lock *lock)
{
        int do_ast;

        LDLM_DEBUG(lock, "client blocking AST callback handler");

        lock_res_and_lock(lock);
        lock->l_flags |= LDLM_FL_CBPENDING;

        if (lock->l_flags & LDLM_FL_CANCEL_ON_BLOCK)
                lock->l_flags |= LDLM_FL_CANCEL;

        do_ast = !lock->l_readers && !lock->l_writers;
        unlock_res_and_lock(lock);

        if (do_ast) {
                CDEBUG(D_DLMTRACE,
                       "Lock %p already unused, calling callback (%p)\n", lock,
                       lock->l_blocking_ast);
                if (lock->l_blocking_ast != NULL)
                        lock->l_blocking_ast(lock, ld, lock->l_ast_data,
                                             LDLM_CB_BLOCKING);
        } else {
                CDEBUG(D_DLMTRACE,
                       "Lock %p is referenced, will be cancelled later\n",
                       lock);
        }

        LDLM_DEBUG(lock, "client blocking callback handler END");
        LDLM_LOCK_RELEASE(lock);
}

/**
 * Callback handler for receiving incoming completion ASTs.
 *
 * This only can happen on client side.
 */
static void ldlm_handle_cp_callback(struct ptlrpc_request *req,
                                    struct ldlm_namespace *ns,
                                    struct ldlm_request *dlm_req,
                                    struct ldlm_lock *lock)
{
        int lvb_len;
        LIST_HEAD(ast_list);
        int rc = 0;

        LDLM_DEBUG(lock, "client completion callback handler START");

        if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_CANCEL_BL_CB_RACE)) {
                int to = cfs_time_seconds(1);

                while (to > 0) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        schedule_timeout(to);
                        if (lock->l_granted_mode == lock->l_req_mode ||
                            lock->l_flags & LDLM_FL_DESTROYED)
                                break;
                }
        }

        lvb_len = req_capsule_get_size(&req->rq_pill, &RMF_DLM_LVB, RCL_CLIENT);
        if (lvb_len < 0) {
                LDLM_ERROR(lock, "Fail to get lvb_len, rc = %d", lvb_len);
                rc = lvb_len;
                goto out;
        } else if (lvb_len > 0) {
                if (lock->l_lvb_len > 0) {
                        /* for extent lock, lvb contains ost_lvb{}. */
                        LASSERT(lock->l_lvb_data != NULL);

                        if (unlikely(lock->l_lvb_len < lvb_len)) {
                                LDLM_ERROR(lock, "Replied LVB is larger than expectation, expected = %d, replied = %d",
                                           lock->l_lvb_len, lvb_len);
                                rc = -EINVAL;
                                goto out;
                        }
                } else if (ldlm_has_layout(lock)) { /* for layout lock, lvb has
                                                     * variable length */
                        void *lvb_data;

                        lvb_data = kzalloc(lvb_len, GFP_NOFS);
                        if (!lvb_data) {
                                LDLM_ERROR(lock, "No memory: %d.\n", lvb_len);
                                rc = -ENOMEM;
                                goto out;
                        }

                        lock_res_and_lock(lock);
                        LASSERT(lock->l_lvb_data == NULL);
                        lock->l_lvb_type = LVB_T_LAYOUT;
                        lock->l_lvb_data = lvb_data;
                        lock->l_lvb_len = lvb_len;
                        unlock_res_and_lock(lock);
                }
        }

        lock_res_and_lock(lock);
        if ((lock->l_flags & LDLM_FL_DESTROYED) ||
            lock->l_granted_mode == lock->l_req_mode) {
                /* bug 11300: the lock has already been granted */
                unlock_res_and_lock(lock);
                LDLM_DEBUG(lock, "Double grant race happened");
                rc = 0;
                goto out;
        }

        /* If we receive the completion AST before the actual enqueue returned,
         * then we might need to switch lock modes, resources, or extents. */
        if (dlm_req->lock_desc.l_granted_mode != lock->l_req_mode) {
                lock->l_req_mode = dlm_req->lock_desc.l_granted_mode;
                LDLM_DEBUG(lock, "completion AST, new lock mode");
        }

        if (lock->l_resource->lr_type != LDLM_PLAIN) {
                ldlm_convert_policy_to_local(req->rq_export,
                                          dlm_req->lock_desc.l_resource.lr_type,
                                          &dlm_req->lock_desc.l_policy_data,
                                          &lock->l_policy_data);
                LDLM_DEBUG(lock, "completion AST, new policy data");
        }

        ldlm_resource_unlink_lock(lock);
        if (memcmp(&dlm_req->lock_desc.l_resource.lr_name,
                   &lock->l_resource->lr_name,
                   sizeof(lock->l_resource->lr_name)) != 0) {
                unlock_res_and_lock(lock);
                rc = ldlm_lock_change_resource(ns, lock,
                                &dlm_req->lock_desc.l_resource.lr_name);
                if (rc < 0) {
                        LDLM_ERROR(lock, "Failed to allocate resource");
                        goto out;
                }
                LDLM_DEBUG(lock, "completion AST, new resource");
                CERROR("change resource!\n");
                lock_res_and_lock(lock);
        }

        if (dlm_req->lock_flags & LDLM_FL_AST_SENT) {
                /* BL_AST locks are not needed in LRU.
                 * Let ldlm_cancel_lru() be fast. */
                ldlm_lock_remove_from_lru(lock);
                lock->l_flags |= LDLM_FL_CBPENDING | LDLM_FL_BL_AST;
                LDLM_DEBUG(lock, "completion AST includes blocking AST");
        }

        if (lock->l_lvb_len > 0) {
                rc = ldlm_fill_lvb(lock, &req->rq_pill, RCL_CLIENT,
                                   lock->l_lvb_data, lvb_len);
                if (rc < 0) {
                        unlock_res_and_lock(lock);
                        goto out;
                }
        }

        ldlm_grant_lock(lock, &ast_list);
        unlock_res_and_lock(lock);

        LDLM_DEBUG(lock, "callback handler finished, about to run_ast_work");

        /* Let Enqueue to call osc_lock_upcall() and initialize
         * l_ast_data */
        OBD_FAIL_TIMEOUT(OBD_FAIL_OSC_CP_ENQ_RACE, 2);

        ldlm_run_ast_work(ns, &ast_list, LDLM_WORK_CP_AST);

        LDLM_DEBUG_NOLOCK("client completion callback handler END (lock %p)",
                          lock);
        goto out;

out:
        if (rc < 0) {
                lock_res_and_lock(lock);
                lock->l_flags |= LDLM_FL_FAILED;
                unlock_res_and_lock(lock);
                wake_up(&lock->l_waitq);
        }
        LDLM_LOCK_RELEASE(lock);
}

/**
 * Callback handler for receiving incoming glimpse ASTs.
 *
 * This only can happen on client side.  After handling the glimpse AST
 * we also consider dropping the lock here if it is unused locally for a
 * long time.
 */
static void ldlm_handle_gl_callback(struct ptlrpc_request *req,
                                    struct ldlm_namespace *ns,
                                    struct ldlm_request *dlm_req,
                                    struct ldlm_lock *lock)
{
        int rc = -ENOSYS;

        LDLM_DEBUG(lock, "client glimpse AST callback handler");

        if (lock->l_glimpse_ast != NULL)
                rc = lock->l_glimpse_ast(lock, req);

        if (req->rq_repmsg != NULL) {
                ptlrpc_reply(req);
        } else {
                req->rq_status = rc;
                ptlrpc_error(req);
        }

        lock_res_and_lock(lock);
        if (lock->l_granted_mode == LCK_PW &&
            !lock->l_readers && !lock->l_writers &&
            cfs_time_after(cfs_time_current(),
                           cfs_time_add(lock->l_last_used,
                                        cfs_time_seconds(10)))) {
                unlock_res_and_lock(lock);
                if (ldlm_bl_to_thread_lock(ns, NULL, lock))
                        ldlm_handle_bl_callback(ns, NULL, lock);

                return;
        }
        unlock_res_and_lock(lock);
        LDLM_LOCK_RELEASE(lock);
}

static int ldlm_callback_reply(struct ptlrpc_request *req, int rc)
{
        if (req->rq_no_reply)
                return 0;

        req->rq_status = rc;
        if (!req->rq_packed_final) {
                rc = lustre_pack_reply(req, 1, NULL, NULL);
                if (rc)
                        return rc;
        }
        return ptlrpc_reply(req);
}

static int __ldlm_bl_to_thread(struct ldlm_bl_work_item *blwi,
                               ldlm_cancel_flags_t cancel_flags)
{
        struct ldlm_bl_pool *blp = ldlm_state->ldlm_bl_pool;

        spin_lock(&blp->blp_lock);
        if (blwi->blwi_lock &&
            blwi->blwi_lock->l_flags & LDLM_FL_DISCARD_DATA) {
                /* add LDLM_FL_DISCARD_DATA requests to the priority list */
                list_add_tail(&blwi->blwi_entry, &blp->blp_prio_list);
        } else {
                /* other blocking callbacks are added to the regular list */
                list_add_tail(&blwi->blwi_entry, &blp->blp_list);
        }
        spin_unlock(&blp->blp_lock);

        wake_up(&blp->blp_waitq);

        /* can not check blwi->blwi_flags as blwi could be already freed in
           LCF_ASYNC mode */
        if (!(cancel_flags & LCF_ASYNC))
                wait_for_completion(&blwi->blwi_comp);

        return 0;
}

static inline void init_blwi(struct ldlm_bl_work_item *blwi,
                             struct ldlm_namespace *ns,
                             struct ldlm_lock_desc *ld,
                             struct list_head *cancels, int count,
                             struct ldlm_lock *lock,
                             ldlm_cancel_flags_t cancel_flags)
{
        init_completion(&blwi->blwi_comp);
        INIT_LIST_HEAD(&blwi->blwi_head);

        if (memory_pressure_get())
                blwi->blwi_mem_pressure = 1;

        blwi->blwi_ns = ns;
        blwi->blwi_flags = cancel_flags;
        if (ld != NULL)
                blwi->blwi_ld = *ld;
        if (count) {
                list_add(&blwi->blwi_head, cancels);
                list_del_init(cancels);
                blwi->blwi_count = count;
        } else {
                blwi->blwi_lock = lock;
        }
}

/**
 * Queues a list of locks \a cancels containing \a count locks
 * for later processing by a blocking thread.  If \a count is zero,
 * then the lock referenced as \a lock is queued instead.
 *
 * The blocking thread would then call ->l_blocking_ast callback in the lock.
 * If list addition fails an error is returned and caller is supposed to
 * call ->l_blocking_ast itself.
 */
static int ldlm_bl_to_thread(struct ldlm_namespace *ns,
                             struct ldlm_lock_desc *ld,
                             struct ldlm_lock *lock,
                             struct list_head *cancels, int count,
                             ldlm_cancel_flags_t cancel_flags)
{
        if (cancels && count == 0)
                return 0;

        if (cancel_flags & LCF_ASYNC) {
                struct ldlm_bl_work_item *blwi;

                blwi = kzalloc(sizeof(*blwi), GFP_NOFS);
                if (!blwi)
                        return -ENOMEM;
                init_blwi(blwi, ns, ld, cancels, count, lock, cancel_flags);

                return __ldlm_bl_to_thread(blwi, cancel_flags);
        } else {
                /* if it is synchronous call do minimum mem alloc, as it could
                 * be triggered from kernel shrinker
                 */
                struct ldlm_bl_work_item blwi;

                memset(&blwi, 0, sizeof(blwi));
                init_blwi(&blwi, ns, ld, cancels, count, lock, cancel_flags);
                return __ldlm_bl_to_thread(&blwi, cancel_flags);
        }
}

int ldlm_bl_to_thread_lock(struct ldlm_namespace *ns, struct ldlm_lock_desc *ld,
                           struct ldlm_lock *lock)
{
        return ldlm_bl_to_thread(ns, ld, lock, NULL, 0, LCF_ASYNC);
}

int ldlm_bl_to_thread_list(struct ldlm_namespace *ns, struct ldlm_lock_desc *ld,
                           struct list_head *cancels, int count,
                           ldlm_cancel_flags_t cancel_flags)
{
        return ldlm_bl_to_thread(ns, ld, NULL, cancels, count, cancel_flags);
}

/* Setinfo coming from Server (eg MDT) to Client (eg MDC)! */
static int ldlm_handle_setinfo(struct ptlrpc_request *req)
{
        struct obd_device *obd = req->rq_export->exp_obd;
        char *key;
        void *val;
        int keylen, vallen;
        int rc = -ENOSYS;

        DEBUG_REQ(D_HSM, req, "%s: handle setinfo\n", obd->obd_name);

        req_capsule_set(&req->rq_pill, &RQF_OBD_SET_INFO);

        key = req_capsule_client_get(&req->rq_pill, &RMF_SETINFO_KEY);
        if (key == NULL) {
                DEBUG_REQ(D_IOCTL, req, "no set_info key");
                return -EFAULT;
        }
        keylen = req_capsule_get_size(&req->rq_pill, &RMF_SETINFO_KEY,
                                      RCL_CLIENT);
        val = req_capsule_client_get(&req->rq_pill, &RMF_SETINFO_VAL);
        if (val == NULL) {
                DEBUG_REQ(D_IOCTL, req, "no set_info val");
                return -EFAULT;
        }
        vallen = req_capsule_get_size(&req->rq_pill, &RMF_SETINFO_VAL,
                                      RCL_CLIENT);

        /* We are responsible for swabbing contents of val */

        if (KEY_IS(KEY_HSM_COPYTOOL_SEND))
                /* Pass it on to mdc (the "export" in this case) */
                rc = obd_set_info_async(req->rq_svc_thread->t_env,
                                        req->rq_export,
                                        sizeof(KEY_HSM_COPYTOOL_SEND),
                                        KEY_HSM_COPYTOOL_SEND,
                                        vallen, val, NULL);
        else
                DEBUG_REQ(D_WARNING, req, "ignoring unknown key %s", key);

        return rc;
}

static inline void ldlm_callback_errmsg(struct ptlrpc_request *req,
                                        const char *msg, int rc,
                                        struct lustre_handle *handle)
{
        DEBUG_REQ((req->rq_no_reply || rc) ? D_WARNING : D_DLMTRACE, req,
                  "%s: [nid %s] [rc %d] [lock %#llx]",
                  msg, libcfs_id2str(req->rq_peer), rc,
                  handle ? handle->cookie : 0);
        if (req->rq_no_reply)
                CWARN("No reply was sent, maybe cause bug 21636.\n");
        else if (rc)
                CWARN("Send reply failed, maybe cause bug 21636.\n");
}

static int ldlm_handle_qc_callback(struct ptlrpc_request *req)
{
        struct obd_quotactl *oqctl;
        struct client_obd *cli = &req->rq_export->exp_obd->u.cli;

        oqctl = req_capsule_client_get(&req->rq_pill, &RMF_OBD_QUOTACTL);
        if (oqctl == NULL) {
                CERROR("Can't unpack obd_quotactl\n");
                return -EPROTO;
        }

        oqctl->qc_stat = ptlrpc_status_ntoh(oqctl->qc_stat);

        cli->cl_qchk_stat = oqctl->qc_stat;
        return 0;
}

/* TODO: handle requests in a similar way as MDT: see mdt_handle_common() */
static int ldlm_callback_handler(struct ptlrpc_request *req)
{
        struct ldlm_namespace *ns;
        struct ldlm_request *dlm_req;
        struct ldlm_lock *lock;
        int rc;

        /* Requests arrive in sender's byte order.  The ptlrpc service
         * handler has already checked and, if necessary, byte-swapped the
         * incoming request message body, but I am responsible for the
         * message buffers. */

        /* do nothing for sec context finalize */
        if (lustre_msg_get_opc(req->rq_reqmsg) == SEC_CTX_FINI)
                return 0;

        req_capsule_init(&req->rq_pill, req, RCL_SERVER);

        if (req->rq_export == NULL) {
                rc = ldlm_callback_reply(req, -ENOTCONN);
                ldlm_callback_errmsg(req, "Operate on unconnected server",
                                     rc, NULL);
                return 0;
        }

        LASSERT(req->rq_export != NULL);
        LASSERT(req->rq_export->exp_obd != NULL);

        switch (lustre_msg_get_opc(req->rq_reqmsg)) {
        case LDLM_BL_CALLBACK:
                if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_BL_CALLBACK_NET))
                        return 0;
                break;
        case LDLM_CP_CALLBACK:
                if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_CP_CALLBACK_NET))
                        return 0;
                break;
        case LDLM_GL_CALLBACK:
                if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_GL_CALLBACK_NET))
                        return 0;
                break;
        case LDLM_SET_INFO:
                rc = ldlm_handle_setinfo(req);
                ldlm_callback_reply(req, rc);
                return 0;
        case OBD_QC_CALLBACK:
                req_capsule_set(&req->rq_pill, &RQF_QC_CALLBACK);
                if (OBD_FAIL_CHECK(OBD_FAIL_OBD_QC_CALLBACK_NET))
                        return 0;
                rc = ldlm_handle_qc_callback(req);
                ldlm_callback_reply(req, rc);
                return 0;
        default:
                CERROR("unknown opcode %u\n",
                       lustre_msg_get_opc(req->rq_reqmsg));
                ldlm_callback_reply(req, -EPROTO);
                return 0;
        }

        ns = req->rq_export->exp_obd->obd_namespace;
        LASSERT(ns != NULL);

        req_capsule_set(&req->rq_pill, &RQF_LDLM_CALLBACK);

        dlm_req = req_capsule_client_get(&req->rq_pill, &RMF_DLM_REQ);
        if (dlm_req == NULL) {
                rc = ldlm_callback_reply(req, -EPROTO);
                ldlm_callback_errmsg(req, "Operate without parameter", rc,
                                     NULL);
                return 0;
        }

        /* Force a known safe race, send a cancel to the server for a lock
         * which the server has already started a blocking callback on. */
        if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_CANCEL_BL_CB_RACE) &&
            lustre_msg_get_opc(req->rq_reqmsg) == LDLM_BL_CALLBACK) {
                rc = ldlm_cli_cancel(&dlm_req->lock_handle[0], 0);
                if (rc < 0)
                        CERROR("ldlm_cli_cancel: %d\n", rc);
        }

        lock = ldlm_handle2lock_long(&dlm_req->lock_handle[0], 0);
        if (!lock) {
                CDEBUG(D_DLMTRACE, "callback on lock %#llx - lock disappeared\n",
                       dlm_req->lock_handle[0].cookie);
                rc = ldlm_callback_reply(req, -EINVAL);
                ldlm_callback_errmsg(req, "Operate with invalid parameter", rc,
                                     &dlm_req->lock_handle[0]);
                return 0;
        }

        if ((lock->l_flags & LDLM_FL_FAIL_LOC) &&
            lustre_msg_get_opc(req->rq_reqmsg) == LDLM_BL_CALLBACK)
                OBD_RACE(OBD_FAIL_LDLM_CP_BL_RACE);

        /* Copy hints/flags (e.g. LDLM_FL_DISCARD_DATA) from AST. */
        lock_res_and_lock(lock);
        lock->l_flags |= ldlm_flags_from_wire(dlm_req->lock_flags &
                                              LDLM_AST_FLAGS);
        if (lustre_msg_get_opc(req->rq_reqmsg) == LDLM_BL_CALLBACK) {
                /* If somebody cancels lock and cache is already dropped,
                 * or lock is failed before cp_ast received on client,
                 * we can tell the server we have no lock. Otherwise, we
                 * should send cancel after dropping the cache. */
                if (((lock->l_flags & LDLM_FL_CANCELING) &&
                    (lock->l_flags & LDLM_FL_BL_DONE)) ||
                    (lock->l_flags & LDLM_FL_FAILED)) {
                        LDLM_DEBUG(lock, "callback on lock %#llx - lock disappeared\n",
                                   dlm_req->lock_handle[0].cookie);
                        unlock_res_and_lock(lock);
                        LDLM_LOCK_RELEASE(lock);
                        rc = ldlm_callback_reply(req, -EINVAL);
                        ldlm_callback_errmsg(req, "Operate on stale lock", rc,
                                             &dlm_req->lock_handle[0]);
                        return 0;
                }
                /* BL_AST locks are not needed in LRU.
                 * Let ldlm_cancel_lru() be fast. */
                ldlm_lock_remove_from_lru(lock);
                lock->l_flags |= LDLM_FL_BL_AST;
        }
        unlock_res_and_lock(lock);

        /* We want the ost thread to get this reply so that it can respond
         * to ost requests (write cache writeback) that might be triggered
         * in the callback.
         *
         * But we'd also like to be able to indicate in the reply that we're
         * cancelling right now, because it's unused, or have an intent result
         * in the reply, so we might have to push the responsibility for sending
         * the reply down into the AST handlers, alas. */

        switch (lustre_msg_get_opc(req->rq_reqmsg)) {
        case LDLM_BL_CALLBACK:
                CDEBUG(D_INODE, "blocking ast\n");
                req_capsule_extend(&req->rq_pill, &RQF_LDLM_BL_CALLBACK);
                if (!(lock->l_flags & LDLM_FL_CANCEL_ON_BLOCK)) {
                        rc = ldlm_callback_reply(req, 0);
                        if (req->rq_no_reply || rc)
                                ldlm_callback_errmsg(req, "Normal process", rc,
                                                     &dlm_req->lock_handle[0]);
                }
                if (ldlm_bl_to_thread_lock(ns, &dlm_req->lock_desc, lock))
                        ldlm_handle_bl_callback(ns, &dlm_req->lock_desc, lock);
                break;
        case LDLM_CP_CALLBACK:
                CDEBUG(D_INODE, "completion ast\n");
                req_capsule_extend(&req->rq_pill, &RQF_LDLM_CP_CALLBACK);
                ldlm_callback_reply(req, 0);
                ldlm_handle_cp_callback(req, ns, dlm_req, lock);
                break;
        case LDLM_GL_CALLBACK:
                CDEBUG(D_INODE, "glimpse ast\n");
                req_capsule_extend(&req->rq_pill, &RQF_LDLM_GL_CALLBACK);
                ldlm_handle_gl_callback(req, ns, dlm_req, lock);
                break;
        default:
                LBUG();                  /* checked above */
        }

        return 0;
}

static struct ldlm_bl_work_item *ldlm_bl_get_work(struct ldlm_bl_pool *blp)
{
        struct ldlm_bl_work_item *blwi = NULL;
        static unsigned int num_bl;

        spin_lock(&blp->blp_lock);
        /* process a request from the blp_list at least every blp_num_threads */
        if (!list_empty(&blp->blp_list) &&
            (list_empty(&blp->blp_prio_list) || num_bl == 0))
                blwi = list_entry(blp->blp_list.next,
                                      struct ldlm_bl_work_item, blwi_entry);
        else
                if (!list_empty(&blp->blp_prio_list))
                        blwi = list_entry(blp->blp_prio_list.next,
                                              struct ldlm_bl_work_item,
                                              blwi_entry);

        if (blwi) {
                if (++num_bl >= atomic_read(&blp->blp_num_threads))
                        num_bl = 0;
                list_del(&blwi->blwi_entry);
        }
        spin_unlock(&blp->blp_lock);

        return blwi;
}

/* This only contains temporary data until the thread starts */
struct ldlm_bl_thread_data {
        char                    bltd_name[CFS_CURPROC_COMM_MAX];
        struct ldlm_bl_pool     *bltd_blp;
        struct completion       bltd_comp;
        int                     bltd_num;
};

static int ldlm_bl_thread_main(void *arg);

static int ldlm_bl_thread_start(struct ldlm_bl_pool *blp)
{
        struct ldlm_bl_thread_data bltd = { .bltd_blp = blp };
        struct task_struct *task;

        init_completion(&bltd.bltd_comp);
        bltd.bltd_num = atomic_read(&blp->blp_num_threads);
        snprintf(bltd.bltd_name, sizeof(bltd.bltd_name),
                "ldlm_bl_%02d", bltd.bltd_num);
        task = kthread_run(ldlm_bl_thread_main, &bltd, "%s", bltd.bltd_name);
        if (IS_ERR(task)) {
                CERROR("cannot start LDLM thread ldlm_bl_%02d: rc %ld\n",
                       atomic_read(&blp->blp_num_threads), PTR_ERR(task));
                return PTR_ERR(task);
        }
        wait_for_completion(&bltd.bltd_comp);

        return 0;
}

/**
 * Main blocking requests processing thread.
 *
 * Callers put locks into its queue by calling ldlm_bl_to_thread.
 * This thread in the end ends up doing actual call to ->l_blocking_ast
 * for queued locks.
 */
static int ldlm_bl_thread_main(void *arg)
{
        struct ldlm_bl_pool *blp;

        {
                struct ldlm_bl_thread_data *bltd = arg;

                blp = bltd->bltd_blp;

                atomic_inc(&blp->blp_num_threads);
                atomic_inc(&blp->blp_busy_threads);

                complete(&bltd->bltd_comp);
                /* cannot use bltd after this, it is only on caller's stack */
        }

        while (1) {
                struct l_wait_info lwi = { 0 };
                struct ldlm_bl_work_item *blwi = NULL;
                int busy;

                blwi = ldlm_bl_get_work(blp);

                if (blwi == NULL) {
                        atomic_dec(&blp->blp_busy_threads);
                        l_wait_event_exclusive(blp->blp_waitq,
                                         (blwi = ldlm_bl_get_work(blp)) != NULL,
                                         &lwi);
                        busy = atomic_inc_return(&blp->blp_busy_threads);
                } else {
                        busy = atomic_read(&blp->blp_busy_threads);
                }

                if (blwi->blwi_ns == NULL)
                        /* added by ldlm_cleanup() */
                        break;

                /* Not fatal if racy and have a few too many threads */
                if (unlikely(busy < blp->blp_max_threads &&
                             busy >= atomic_read(&blp->blp_num_threads) &&
                             !blwi->blwi_mem_pressure))
                        /* discard the return value, we tried */
                        ldlm_bl_thread_start(blp);

                if (blwi->blwi_mem_pressure)
                        memory_pressure_set();

                if (blwi->blwi_count) {
                        int count;
                        /* The special case when we cancel locks in LRU
                         * asynchronously, we pass the list of locks here.
                         * Thus locks are marked LDLM_FL_CANCELING, but NOT
                         * canceled locally yet. */
                        count = ldlm_cli_cancel_list_local(&blwi->blwi_head,
                                                           blwi->blwi_count,
                                                           LCF_BL_AST);
                        ldlm_cli_cancel_list(&blwi->blwi_head, count, NULL,
                                             blwi->blwi_flags);
                } else {
                        ldlm_handle_bl_callback(blwi->blwi_ns, &blwi->blwi_ld,
                                                blwi->blwi_lock);
                }
                if (blwi->blwi_mem_pressure)
                        memory_pressure_clr();

                if (blwi->blwi_flags & LCF_ASYNC)
                        kfree(blwi);
                else
                        complete(&blwi->blwi_comp);
        }

        atomic_dec(&blp->blp_busy_threads);
        atomic_dec(&blp->blp_num_threads);
        complete(&blp->blp_comp);
        return 0;
}

static int ldlm_setup(void);
static int ldlm_cleanup(void);

int ldlm_get_ref(void)
{
        int rc = 0;

        mutex_lock(&ldlm_ref_mutex);
        if (++ldlm_refcount == 1) {
                rc = ldlm_setup();
                if (rc)
                        ldlm_refcount--;
        }
        mutex_unlock(&ldlm_ref_mutex);

        return rc;
}
EXPORT_SYMBOL(ldlm_get_ref);

void ldlm_put_ref(void)
{
        mutex_lock(&ldlm_ref_mutex);
        if (ldlm_refcount == 1) {
                int rc = ldlm_cleanup();

                if (rc)
                        CERROR("ldlm_cleanup failed: %d\n", rc);
                else
                        ldlm_refcount--;
        } else {
                ldlm_refcount--;
        }
        mutex_unlock(&ldlm_ref_mutex);
}
EXPORT_SYMBOL(ldlm_put_ref);

extern unsigned int ldlm_cancel_unused_locks_before_replay;

static ssize_t cancel_unused_locks_before_replay_show(struct kobject *kobj,
                                                      struct attribute *attr,
                                                      char *buf)
{
        return sprintf(buf, "%d\n", ldlm_cancel_unused_locks_before_replay);
}

static ssize_t cancel_unused_locks_before_replay_store(struct kobject *kobj,
                                                       struct attribute *attr,
                                                       const char *buffer,
                                                       size_t count)
{
        int rc;
        unsigned long val;

        rc = kstrtoul(buffer, 10, &val);
        if (rc)
                return rc;

        ldlm_cancel_unused_locks_before_replay = val;

        return count;
}
LUSTRE_RW_ATTR(cancel_unused_locks_before_replay);

/* These are for root of /sys/fs/lustre/ldlm */
static struct attribute *ldlm_attrs[] = {
        &lustre_attr_cancel_unused_locks_before_replay.attr,
        NULL,
};

static struct attribute_group ldlm_attr_group = {
        .attrs = ldlm_attrs,
};

static int ldlm_setup(void)
{
        static struct ptlrpc_service_conf       conf;
        struct ldlm_bl_pool                     *blp = NULL;
        int rc = 0;
        int i;

        if (ldlm_state != NULL)
                return -EALREADY;

        ldlm_state = kzalloc(sizeof(*ldlm_state), GFP_NOFS);
        if (!ldlm_state)
                return -ENOMEM;

        ldlm_kobj = kobject_create_and_add("ldlm", lustre_kobj);
        if (!ldlm_kobj) {
                rc = -ENOMEM;
                goto out;
        }

        rc = sysfs_create_group(ldlm_kobj, &ldlm_attr_group);
        if (rc)
                goto out;

        ldlm_ns_kset = kset_create_and_add("namespaces", NULL, ldlm_kobj);
        if (!ldlm_ns_kset) {
                rc = -ENOMEM;
                goto out;
        }

        ldlm_svc_kset = kset_create_and_add("services", NULL, ldlm_kobj);
        if (!ldlm_svc_kset) {
                rc = -ENOMEM;
                goto out;
        }

        rc = ldlm_debugfs_setup();
        if (rc != 0)
                goto out;

        memset(&conf, 0, sizeof(conf));
        conf = (typeof(conf)) {
                .psc_name               = "ldlm_cbd",
                .psc_watchdog_factor    = 2,
                .psc_buf                = {
                        .bc_nbufs               = LDLM_CLIENT_NBUFS,
                        .bc_buf_size            = LDLM_BUFSIZE,
                        .bc_req_max_size        = LDLM_MAXREQSIZE,
                        .bc_rep_max_size        = LDLM_MAXREPSIZE,
                        .bc_req_portal          = LDLM_CB_REQUEST_PORTAL,
                        .bc_rep_portal          = LDLM_CB_REPLY_PORTAL,
                },
                .psc_thr                = {
                        .tc_thr_name            = "ldlm_cb",
                        .tc_thr_factor          = LDLM_THR_FACTOR,
                        .tc_nthrs_init          = LDLM_NTHRS_INIT,
                        .tc_nthrs_base          = LDLM_NTHRS_BASE,
                        .tc_nthrs_max           = LDLM_NTHRS_MAX,
                        .tc_nthrs_user          = ldlm_num_threads,
                        .tc_cpu_affinity        = 1,
                        .tc_ctx_tags            = LCT_MD_THREAD | LCT_DT_THREAD,
                },
                .psc_cpt                = {
                        .cc_pattern             = ldlm_cpts,
                },
                .psc_ops                = {
                        .so_req_handler         = ldlm_callback_handler,
                },
        };
        ldlm_state->ldlm_cb_service =
                        ptlrpc_register_service(&conf, ldlm_svc_kset,
                                                ldlm_svc_debugfs_dir);
        if (IS_ERR(ldlm_state->ldlm_cb_service)) {
                CERROR("failed to start service\n");
                rc = PTR_ERR(ldlm_state->ldlm_cb_service);
                ldlm_state->ldlm_cb_service = NULL;
                goto out;
        }

        blp = kzalloc(sizeof(*blp), GFP_NOFS);
        if (!blp) {
                rc = -ENOMEM;
                goto out;
        }
        ldlm_state->ldlm_bl_pool = blp;

        spin_lock_init(&blp->blp_lock);
        INIT_LIST_HEAD(&blp->blp_list);
        INIT_LIST_HEAD(&blp->blp_prio_list);
        init_waitqueue_head(&blp->blp_waitq);
        atomic_set(&blp->blp_num_threads, 0);
        atomic_set(&blp->blp_busy_threads, 0);

        if (ldlm_num_threads == 0) {
                blp->blp_min_threads = LDLM_NTHRS_INIT;
                blp->blp_max_threads = LDLM_NTHRS_MAX;
        } else {
                blp->blp_min_threads = blp->blp_max_threads =
                        min_t(int, LDLM_NTHRS_MAX, max_t(int, LDLM_NTHRS_INIT,
                                                         ldlm_num_threads));
        }

        for (i = 0; i < blp->blp_min_threads; i++) {
                rc = ldlm_bl_thread_start(blp);
                if (rc < 0)
                        goto out;
        }

        rc = ldlm_pools_init();
        if (rc) {
                CERROR("Failed to initialize LDLM pools: %d\n", rc);
                goto out;
        }
        return 0;

 out:
        ldlm_cleanup();
        return rc;
}

static int ldlm_cleanup(void)
{
        if (!list_empty(ldlm_namespace_list(LDLM_NAMESPACE_SERVER)) ||
            !list_empty(ldlm_namespace_list(LDLM_NAMESPACE_CLIENT))) {
                CERROR("ldlm still has namespaces; clean these up first.\n");
                ldlm_dump_all_namespaces(LDLM_NAMESPACE_SERVER, D_DLMTRACE);
                ldlm_dump_all_namespaces(LDLM_NAMESPACE_CLIENT, D_DLMTRACE);
                return -EBUSY;
        }

        ldlm_pools_fini();

        if (ldlm_state->ldlm_bl_pool != NULL) {
                struct ldlm_bl_pool *blp = ldlm_state->ldlm_bl_pool;

                while (atomic_read(&blp->blp_num_threads) > 0) {
                        struct ldlm_bl_work_item blwi = { .blwi_ns = NULL };

                        init_completion(&blp->blp_comp);

                        spin_lock(&blp->blp_lock);
                        list_add_tail(&blwi.blwi_entry, &blp->blp_list);
                        wake_up(&blp->blp_waitq);
                        spin_unlock(&blp->blp_lock);

                        wait_for_completion(&blp->blp_comp);
                }

                kfree(blp);
        }

        if (ldlm_state->ldlm_cb_service != NULL)
                ptlrpc_unregister_service(ldlm_state->ldlm_cb_service);

        if (ldlm_ns_kset)
                kset_unregister(ldlm_ns_kset);
        if (ldlm_svc_kset)
                kset_unregister(ldlm_svc_kset);
        if (ldlm_kobj)
                kobject_put(ldlm_kobj);

        ldlm_debugfs_cleanup();

        kfree(ldlm_state);
        ldlm_state = NULL;

        return 0;
}

int ldlm_init(void)
{
        mutex_init(&ldlm_ref_mutex);
        mutex_init(ldlm_namespace_lock(LDLM_NAMESPACE_SERVER));
        mutex_init(ldlm_namespace_lock(LDLM_NAMESPACE_CLIENT));
        ldlm_resource_slab = kmem_cache_create("ldlm_resources",
                                               sizeof(struct ldlm_resource), 0,
                                               SLAB_HWCACHE_ALIGN, NULL);
        if (ldlm_resource_slab == NULL)
                return -ENOMEM;

        ldlm_lock_slab = kmem_cache_create("ldlm_locks",
                              sizeof(struct ldlm_lock), 0,
                              SLAB_HWCACHE_ALIGN | SLAB_DESTROY_BY_RCU, NULL);
        if (ldlm_lock_slab == NULL) {
                kmem_cache_destroy(ldlm_resource_slab);
                return -ENOMEM;
        }

        ldlm_interval_slab = kmem_cache_create("interval_node",
                                        sizeof(struct ldlm_interval),
                                        0, SLAB_HWCACHE_ALIGN, NULL);
        if (ldlm_interval_slab == NULL) {
                kmem_cache_destroy(ldlm_resource_slab);
                kmem_cache_destroy(ldlm_lock_slab);
                return -ENOMEM;
        }
#if LUSTRE_TRACKS_LOCK_EXP_REFS
        class_export_dump_hook = ldlm_dump_export_locks;
#endif
        return 0;
}

void ldlm_exit(void)
{
        if (ldlm_refcount)
                CERROR("ldlm_refcount is %d in ldlm_exit!\n", ldlm_refcount);
        kmem_cache_destroy(ldlm_resource_slab);
        /* ldlm_lock_put() use RCU to call ldlm_lock_free, so need call
         * synchronize_rcu() to wait a grace period elapsed, so that
         * ldlm_lock_free() get a chance to be called. */
        synchronize_rcu();
        kmem_cache_destroy(ldlm_lock_slab);
        kmem_cache_destroy(ldlm_interval_slab);
}