/*
 * 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) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2015, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/mgc/mgc_request.c
 *
 * Author: Nathan Rutman <nathan@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_MGC
#define D_MGC D_CONFIG /*|D_WARNING*/

#include <linux/module.h>
#include "../include/obd_class.h"
#include "../include/lustre_dlm.h"
#include "../include/lprocfs_status.h"
#include "../include/lustre_log.h"
#include "../include/lustre_disk.h"

#include "mgc_internal.h"

static int mgc_name2resid(char *name, int len, struct ldlm_res_id *res_id,
                          int type)
{
        __u64 resname = 0;

        if (len > sizeof(resname)) {
                CERROR("name too long: %s\n", name);
                return -EINVAL;
        }
        if (len <= 0) {
                CERROR("missing name: %s\n", name);
                return -EINVAL;
        }
        memcpy(&resname, name, len);

        /* Always use the same endianness for the resid */
        memset(res_id, 0, sizeof(*res_id));
        res_id->name[0] = cpu_to_le64(resname);
        /* XXX: unfortunately, sptlprc and config llog share one lock */
        switch (type) {
        case CONFIG_T_CONFIG:
        case CONFIG_T_SPTLRPC:
                resname = 0;
                break;
        case CONFIG_T_RECOVER:
        case CONFIG_T_PARAMS:
                resname = type;
                break;
        default:
                LBUG();
        }
        res_id->name[1] = cpu_to_le64(resname);
        CDEBUG(D_MGC, "log %s to resid %#llx/%#llx (%.8s)\n", name,
               res_id->name[0], res_id->name[1], (char *)&res_id->name[0]);
        return 0;
}

int mgc_fsname2resid(char *fsname, struct ldlm_res_id *res_id, int type)
{
        /* fsname is at most 8 chars long, maybe contain "-".
         * e.g. "lustre", "SUN-000"
         */
        return mgc_name2resid(fsname, strlen(fsname), res_id, type);
}
EXPORT_SYMBOL(mgc_fsname2resid);

static int mgc_logname2resid(char *logname, struct ldlm_res_id *res_id, int type)
{
        char *name_end;
        int len;

        /* logname consists of "fsname-nodetype".
         * e.g. "lustre-MDT0001", "SUN-000-client"
         * there is an exception: llog "params"
         */
        name_end = strrchr(logname, '-');
        if (!name_end)
                len = strlen(logname);
        else
                len = name_end - logname;
        return mgc_name2resid(logname, len, res_id, type);
}

/********************** config llog list **********************/
static LIST_HEAD(config_llog_list);
static DEFINE_SPINLOCK(config_list_lock);

/* Take a reference to a config log */
static int config_log_get(struct config_llog_data *cld)
{
        atomic_inc(&cld->cld_refcount);
        CDEBUG(D_INFO, "log %s refs %d\n", cld->cld_logname,
               atomic_read(&cld->cld_refcount));
        return 0;
}

/* Drop a reference to a config log.  When no longer referenced,
 * we can free the config log data
 */
static void config_log_put(struct config_llog_data *cld)
{
        CDEBUG(D_INFO, "log %s refs %d\n", cld->cld_logname,
               atomic_read(&cld->cld_refcount));
        LASSERT(atomic_read(&cld->cld_refcount) > 0);

        /* spinlock to make sure no item with 0 refcount in the list */
        if (atomic_dec_and_lock(&cld->cld_refcount, &config_list_lock)) {
                list_del(&cld->cld_list_chain);
                spin_unlock(&config_list_lock);

                CDEBUG(D_MGC, "dropping config log %s\n", cld->cld_logname);

                if (cld->cld_recover)
                        config_log_put(cld->cld_recover);
                if (cld->cld_sptlrpc)
                        config_log_put(cld->cld_sptlrpc);
                if (cld->cld_params)
                        config_log_put(cld->cld_params);
                if (cld_is_sptlrpc(cld))
                        sptlrpc_conf_log_stop(cld->cld_logname);

                class_export_put(cld->cld_mgcexp);
                kfree(cld);
        }
}

/* Find a config log by name */
static
struct config_llog_data *config_log_find(char *logname,
                                         struct config_llog_instance *cfg)
{
        struct config_llog_data *cld;
        struct config_llog_data *found = NULL;
        void *instance;

        LASSERT(logname);

        instance = cfg ? cfg->cfg_instance : NULL;
        spin_lock(&config_list_lock);
        list_for_each_entry(cld, &config_llog_list, cld_list_chain) {
                /* check if instance equals */
                if (instance != cld->cld_cfg.cfg_instance)
                        continue;

                /* instance may be NULL, should check name */
                if (strcmp(logname, cld->cld_logname) == 0) {
                        found = cld;
                        break;
                }
        }
        if (found) {
                atomic_inc(&found->cld_refcount);
                LASSERT(found->cld_stopping == 0 || cld_is_sptlrpc(found) == 0);
        }
        spin_unlock(&config_list_lock);
        return found;
}

static
struct config_llog_data *do_config_log_add(struct obd_device *obd,
                                           char *logname,
                                           int type,
                                           struct config_llog_instance *cfg,
                                           struct super_block *sb)
{
        struct config_llog_data *cld;
        int                   rc;

        CDEBUG(D_MGC, "do adding config log %s:%p\n", logname,
               cfg ? cfg->cfg_instance : NULL);

        cld = kzalloc(sizeof(*cld) + strlen(logname) + 1, GFP_NOFS);
        if (!cld)
                return ERR_PTR(-ENOMEM);

        strcpy(cld->cld_logname, logname);
        if (cfg)
                cld->cld_cfg = *cfg;
        else
                cld->cld_cfg.cfg_callback = class_config_llog_handler;
        mutex_init(&cld->cld_lock);
        cld->cld_cfg.cfg_last_idx = 0;
        cld->cld_cfg.cfg_flags = 0;
        cld->cld_cfg.cfg_sb = sb;
        cld->cld_type = type;
        atomic_set(&cld->cld_refcount, 1);

        /* Keep the mgc around until we are done */
        cld->cld_mgcexp = class_export_get(obd->obd_self_export);

        if (cld_is_sptlrpc(cld)) {
                sptlrpc_conf_log_start(logname);
                cld->cld_cfg.cfg_obdname = obd->obd_name;
        }

        rc = mgc_logname2resid(logname, &cld->cld_resid, type);

        spin_lock(&config_list_lock);
        list_add(&cld->cld_list_chain, &config_llog_list);
        spin_unlock(&config_list_lock);

        if (rc) {
                config_log_put(cld);
                return ERR_PTR(rc);
        }

        if (cld_is_sptlrpc(cld)) {
                rc = mgc_process_log(obd, cld);
                if (rc && rc != -ENOENT)
                        CERROR("failed processing sptlrpc log: %d\n", rc);
        }

        return cld;
}

static struct config_llog_data *
config_recover_log_add(struct obd_device *obd, char *fsname,
                       struct config_llog_instance *cfg,
                       struct super_block *sb)
{
        struct config_llog_instance lcfg = *cfg;
        struct config_llog_data *cld;
        char logname[32];

        /* we have to use different llog for clients and mdts for cmd
         * where only clients are notified if one of cmd server restarts
         */
        LASSERT(strlen(fsname) < sizeof(logname) / 2);
        strcpy(logname, fsname);
        LASSERT(lcfg.cfg_instance);
        strcat(logname, "-cliir");

        cld = do_config_log_add(obd, logname, CONFIG_T_RECOVER, &lcfg, sb);
        return cld;
}

static struct config_llog_data *
config_params_log_add(struct obd_device *obd,
                      struct config_llog_instance *cfg, struct super_block *sb)
{
        struct config_llog_instance     lcfg = *cfg;
        struct config_llog_data         *cld;

        lcfg.cfg_instance = sb;

        cld = do_config_log_add(obd, PARAMS_FILENAME, CONFIG_T_PARAMS,
                                &lcfg, sb);

        return cld;
}

/** Add this log to the list of active logs watched by an MGC.
 * Active means we're watching for updates.
 * We have one active log per "mount" - client instance or servername.
 * Each instance may be at a different point in the log.
 */
static int config_log_add(struct obd_device *obd, char *logname,
                          struct config_llog_instance *cfg,
                          struct super_block *sb)
{
        struct lustre_sb_info *lsi = s2lsi(sb);
        struct config_llog_data *cld;
        struct config_llog_data *sptlrpc_cld;
        struct config_llog_data *params_cld;
        char                    seclogname[32];
        char                    *ptr;
        int                     rc;

        CDEBUG(D_MGC, "adding config log %s:%p\n", logname, cfg->cfg_instance);

        /*
         * for each regular log, the depended sptlrpc log name is
         * <fsname>-sptlrpc. multiple regular logs may share one sptlrpc log.
         */
        ptr = strrchr(logname, '-');
        if (!ptr || ptr - logname > 8) {
                CERROR("logname %s is too long\n", logname);
                return -EINVAL;
        }

        memcpy(seclogname, logname, ptr - logname);
        strcpy(seclogname + (ptr - logname), "-sptlrpc");

        sptlrpc_cld = config_log_find(seclogname, NULL);
        if (!sptlrpc_cld) {
                sptlrpc_cld = do_config_log_add(obd, seclogname,
                                                CONFIG_T_SPTLRPC, NULL, NULL);
                if (IS_ERR(sptlrpc_cld)) {
                        CERROR("can't create sptlrpc log: %s\n", seclogname);
                        rc = PTR_ERR(sptlrpc_cld);
                        goto out_err;
                }
        }
        params_cld = config_params_log_add(obd, cfg, sb);
        if (IS_ERR(params_cld)) {
                rc = PTR_ERR(params_cld);
                CERROR("%s: can't create params log: rc = %d\n",
                       obd->obd_name, rc);
                goto out_err1;
        }

        cld = do_config_log_add(obd, logname, CONFIG_T_CONFIG, cfg, sb);
        if (IS_ERR(cld)) {
                CERROR("can't create log: %s\n", logname);
                rc = PTR_ERR(cld);
                goto out_err2;
        }

        cld->cld_sptlrpc = sptlrpc_cld;
        cld->cld_params = params_cld;

        LASSERT(lsi->lsi_lmd);
        if (!(lsi->lsi_lmd->lmd_flags & LMD_FLG_NOIR)) {
                struct config_llog_data *recover_cld;

                ptr = strrchr(seclogname, '-');
                if (ptr) {
                        *ptr = 0;
                } else {
                        CERROR("%s: sptlrpc log name not correct, %s: rc = %d\n",
                               obd->obd_name, seclogname, -EINVAL);
                        config_log_put(cld);
                        return -EINVAL;
                }
                recover_cld = config_recover_log_add(obd, seclogname, cfg, sb);
                if (IS_ERR(recover_cld)) {
                        rc = PTR_ERR(recover_cld);
                        goto out_err3;
                }
                cld->cld_recover = recover_cld;
        }

        return 0;

out_err3:
        config_log_put(cld);

out_err2:
        config_log_put(params_cld);

out_err1:
        config_log_put(sptlrpc_cld);

out_err:
        return rc;
}

DEFINE_MUTEX(llog_process_lock);

/** Stop watching for updates on this log.
 */
static int config_log_end(char *logname, struct config_llog_instance *cfg)
{
        struct config_llog_data *cld;
        struct config_llog_data *cld_sptlrpc = NULL;
        struct config_llog_data *cld_params = NULL;
        struct config_llog_data *cld_recover = NULL;
        int rc = 0;

        cld = config_log_find(logname, cfg);
        if (!cld)
                return -ENOENT;

        mutex_lock(&cld->cld_lock);
        /*
         * if cld_stopping is set, it means we didn't start the log thus
         * not owning the start ref. this can happen after previous umount:
         * the cld still hanging there waiting for lock cancel, and we
         * remount again but failed in the middle and call log_end without
         * calling start_log.
         */
        if (unlikely(cld->cld_stopping)) {
                mutex_unlock(&cld->cld_lock);
                /* drop the ref from the find */
                config_log_put(cld);
                return rc;
        }

        cld->cld_stopping = 1;

        cld_recover = cld->cld_recover;
        cld->cld_recover = NULL;
        mutex_unlock(&cld->cld_lock);

        if (cld_recover) {
                mutex_lock(&cld_recover->cld_lock);
                cld_recover->cld_stopping = 1;
                mutex_unlock(&cld_recover->cld_lock);
                config_log_put(cld_recover);
        }

        spin_lock(&config_list_lock);
        cld_sptlrpc = cld->cld_sptlrpc;
        cld->cld_sptlrpc = NULL;
        cld_params = cld->cld_params;
        cld->cld_params = NULL;
        spin_unlock(&config_list_lock);

        if (cld_sptlrpc)
                config_log_put(cld_sptlrpc);

        if (cld_params) {
                mutex_lock(&cld_params->cld_lock);
                cld_params->cld_stopping = 1;
                mutex_unlock(&cld_params->cld_lock);
                config_log_put(cld_params);
        }

        /* drop the ref from the find */
        config_log_put(cld);
        /* drop the start ref */
        config_log_put(cld);

        CDEBUG(D_MGC, "end config log %s (%d)\n", logname ? logname : "client",
               rc);
        return rc;
}

int lprocfs_mgc_rd_ir_state(struct seq_file *m, void *data)
{
        struct obd_device       *obd = data;
        struct obd_import       *imp;
        struct obd_connect_data *ocd;
        struct config_llog_data *cld;
        int rc;

        rc = lprocfs_climp_check(obd);
        if (rc)
                return rc;

        imp = obd->u.cli.cl_import;
        ocd = &imp->imp_connect_data;

        seq_printf(m, "imperative_recovery: %s\n",
                   OCD_HAS_FLAG(ocd, IMP_RECOV) ? "ENABLED" : "DISABLED");
        seq_printf(m, "client_state:\n");

        spin_lock(&config_list_lock);
        list_for_each_entry(cld, &config_llog_list, cld_list_chain) {
                if (!cld->cld_recover)
                        continue;
                seq_printf(m, "    - { client: %s, nidtbl_version: %u }\n",
                           cld->cld_logname,
                           cld->cld_recover->cld_cfg.cfg_last_idx);
        }
        spin_unlock(&config_list_lock);

        up_read(&obd->u.cli.cl_sem);
        return 0;
}

/* reenqueue any lost locks */
#define RQ_RUNNING 0x1
#define RQ_NOW     0x2
#define RQ_LATER   0x4
#define RQ_STOP    0x8
#define RQ_PRECLEANUP  0x10
static int rq_state;
static wait_queue_head_t            rq_waitq;
static DECLARE_COMPLETION(rq_exit);
static DECLARE_COMPLETION(rq_start);

static void do_requeue(struct config_llog_data *cld)
{
        LASSERT(atomic_read(&cld->cld_refcount) > 0);

        /* Do not run mgc_process_log on a disconnected export or an
         * export which is being disconnected. Take the client
         * semaphore to make the check non-racy.
         */
        down_read(&cld->cld_mgcexp->exp_obd->u.cli.cl_sem);
        if (cld->cld_mgcexp->exp_obd->u.cli.cl_conn_count != 0) {
                CDEBUG(D_MGC, "updating log %s\n", cld->cld_logname);
                mgc_process_log(cld->cld_mgcexp->exp_obd, cld);
        } else {
                CDEBUG(D_MGC, "disconnecting, won't update log %s\n",
                       cld->cld_logname);
        }
        up_read(&cld->cld_mgcexp->exp_obd->u.cli.cl_sem);
}

/* this timeout represents how many seconds MGC should wait before
 * requeue config and recover lock to the MGS. We need to randomize this
 * in order to not flood the MGS.
 */
#define MGC_TIMEOUT_MIN_SECONDS   5
#define MGC_TIMEOUT_RAND_CENTISEC 0x1ff /* ~500 */

static int mgc_requeue_thread(void *data)
{
        bool first = true;

        CDEBUG(D_MGC, "Starting requeue thread\n");

        /* Keep trying failed locks periodically */
        spin_lock(&config_list_lock);
        rq_state |= RQ_RUNNING;
        while (1) {
                struct l_wait_info lwi;
                struct config_llog_data *cld, *cld_prev;
                int rand = cfs_rand() & MGC_TIMEOUT_RAND_CENTISEC;
                int stopped = !!(rq_state & RQ_STOP);
                int to;

                /* Any new or requeued lostlocks will change the state */
                rq_state &= ~(RQ_NOW | RQ_LATER);
                spin_unlock(&config_list_lock);

                if (first) {
                        first = false;
                        complete(&rq_start);
                }

                /* Always wait a few seconds to allow the server who
                 * caused the lock revocation to finish its setup, plus some
                 * random so everyone doesn't try to reconnect at once.
                 */
                to = MGC_TIMEOUT_MIN_SECONDS * HZ;
                to += rand * HZ / 100; /* rand is centi-seconds */
                lwi = LWI_TIMEOUT(to, NULL, NULL);
                l_wait_event(rq_waitq, rq_state & (RQ_STOP | RQ_PRECLEANUP),
                             &lwi);

                /*
                 * iterate & processing through the list. for each cld, process
                 * its depending sptlrpc cld firstly (if any) and then itself.
                 *
                 * it's guaranteed any item in the list must have
                 * reference > 0; and if cld_lostlock is set, at
                 * least one reference is taken by the previous enqueue.
                 */
                cld_prev = NULL;

                spin_lock(&config_list_lock);
                rq_state &= ~RQ_PRECLEANUP;
                list_for_each_entry(cld, &config_llog_list, cld_list_chain) {
                        if (!cld->cld_lostlock)
                                continue;

                        spin_unlock(&config_list_lock);

                        LASSERT(atomic_read(&cld->cld_refcount) > 0);

                        /* Whether we enqueued again or not in mgc_process_log,
                         * we're done with the ref from the old enqueue
                         */
                        if (cld_prev)
                                config_log_put(cld_prev);
                        cld_prev = cld;

                        cld->cld_lostlock = 0;
                        if (likely(!stopped))
                                do_requeue(cld);

                        spin_lock(&config_list_lock);
                }
                spin_unlock(&config_list_lock);
                if (cld_prev)
                        config_log_put(cld_prev);

                /* break after scanning the list so that we can drop
                 * refcount to losing lock clds
                 */
                if (unlikely(stopped)) {
                        spin_lock(&config_list_lock);
                        break;
                }

                /* Wait a bit to see if anyone else needs a requeue */
                lwi = (struct l_wait_info) { 0 };
                l_wait_event(rq_waitq, rq_state & (RQ_NOW | RQ_STOP),
                             &lwi);
                spin_lock(&config_list_lock);
        }
        /* spinlock and while guarantee RQ_NOW and RQ_LATER are not set */
        rq_state &= ~RQ_RUNNING;
        spin_unlock(&config_list_lock);

        complete(&rq_exit);

        CDEBUG(D_MGC, "Ending requeue thread\n");
        return 0;
}

/* Add a cld to the list to requeue.  Start the requeue thread if needed.
 * We are responsible for dropping the config log reference from here on out.
 */
static void mgc_requeue_add(struct config_llog_data *cld)
{
        CDEBUG(D_INFO, "log %s: requeue (r=%d sp=%d st=%x)\n",
               cld->cld_logname, atomic_read(&cld->cld_refcount),
               cld->cld_stopping, rq_state);
        LASSERT(atomic_read(&cld->cld_refcount) > 0);

        mutex_lock(&cld->cld_lock);
        if (cld->cld_stopping || cld->cld_lostlock) {
                mutex_unlock(&cld->cld_lock);
                return;
        }
        /* this refcount will be released in mgc_requeue_thread. */
        config_log_get(cld);
        cld->cld_lostlock = 1;
        mutex_unlock(&cld->cld_lock);

        /* Hold lock for rq_state */
        spin_lock(&config_list_lock);
        if (rq_state & RQ_STOP) {
                spin_unlock(&config_list_lock);
                cld->cld_lostlock = 0;
                config_log_put(cld);
        } else {
                rq_state |= RQ_NOW;
                spin_unlock(&config_list_lock);
                wake_up(&rq_waitq);
        }
}

static int mgc_llog_init(const struct lu_env *env, struct obd_device *obd)
{
        struct llog_ctxt        *ctxt;
        int                      rc;

        /* setup only remote ctxt, the local disk context is switched per each
         * filesystem during mgc_fs_setup()
         */
        rc = llog_setup(env, obd, &obd->obd_olg, LLOG_CONFIG_REPL_CTXT, obd,
                        &llog_client_ops);
        if (rc)
                return rc;

        ctxt = llog_get_context(obd, LLOG_CONFIG_REPL_CTXT);
        LASSERT(ctxt);

        llog_initiator_connect(ctxt);
        llog_ctxt_put(ctxt);

        return 0;
}

static int mgc_llog_fini(const struct lu_env *env, struct obd_device *obd)
{
        struct llog_ctxt *ctxt;

        ctxt = llog_get_context(obd, LLOG_CONFIG_REPL_CTXT);
        if (ctxt)
                llog_cleanup(env, ctxt);

        return 0;
}

static atomic_t mgc_count = ATOMIC_INIT(0);
static int mgc_precleanup(struct obd_device *obd, enum obd_cleanup_stage stage)
{
        int rc = 0;
        int temp;

        switch (stage) {
        case OBD_CLEANUP_EARLY:
                break;
        case OBD_CLEANUP_EXPORTS:
                if (atomic_dec_and_test(&mgc_count)) {
                        LASSERT(rq_state & RQ_RUNNING);
                        /* stop requeue thread */
                        temp = RQ_STOP;
                } else {
                        /* wakeup requeue thread to clean our cld */
                        temp = RQ_NOW | RQ_PRECLEANUP;
                }
                spin_lock(&config_list_lock);
                rq_state |= temp;
                spin_unlock(&config_list_lock);
                wake_up(&rq_waitq);
                if (temp & RQ_STOP)
                        wait_for_completion(&rq_exit);
                obd_cleanup_client_import(obd);
                rc = mgc_llog_fini(NULL, obd);
                if (rc != 0)
                        CERROR("failed to cleanup llogging subsystems\n");
                break;
        }
        return rc;
}

static int mgc_cleanup(struct obd_device *obd)
{
        /* COMPAT_146 - old config logs may have added profiles we don't
         * know about
         */
        if (obd->obd_type->typ_refcnt <= 1)
                /* Only for the last mgc */
                class_del_profiles();

        lprocfs_obd_cleanup(obd);
        ptlrpcd_decref();

        return client_obd_cleanup(obd);
}

static int mgc_setup(struct obd_device *obd, struct lustre_cfg *lcfg)
{
        struct lprocfs_static_vars lvars = { NULL };
        struct task_struct *task;
        int rc;

        ptlrpcd_addref();

        rc = client_obd_setup(obd, lcfg);
        if (rc)
                goto err_decref;

        rc = mgc_llog_init(NULL, obd);
        if (rc) {
                CERROR("failed to setup llogging subsystems\n");
                goto err_cleanup;
        }

        lprocfs_mgc_init_vars(&lvars);
        lprocfs_obd_setup(obd, lvars.obd_vars, lvars.sysfs_vars);
        sptlrpc_lprocfs_cliobd_attach(obd);

        if (atomic_inc_return(&mgc_count) == 1) {
                rq_state = 0;
                init_waitqueue_head(&rq_waitq);

                /* start requeue thread */
                task = kthread_run(mgc_requeue_thread, NULL, "ll_cfg_requeue");
                if (IS_ERR(task)) {
                        rc = PTR_ERR(task);
                        CERROR("%s: cannot start requeue thread: rc = %d; no more log updates\n",
                               obd->obd_name, rc);
                        goto err_cleanup;
                }
                /* rc is the task_struct pointer of mgc_requeue_thread. */
                rc = 0;
                wait_for_completion(&rq_start);
        }

        return rc;

err_cleanup:
        client_obd_cleanup(obd);
err_decref:
        ptlrpcd_decref();
        return rc;
}

/* based on ll_mdc_blocking_ast */
static int mgc_blocking_ast(struct ldlm_lock *lock, struct ldlm_lock_desc *desc,
                            void *data, int flag)
{
        struct lustre_handle lockh;
        struct config_llog_data *cld = data;
        int rc = 0;

        switch (flag) {
        case LDLM_CB_BLOCKING:
                /* mgs wants the lock, give it up... */
                LDLM_DEBUG(lock, "MGC blocking CB");
                ldlm_lock2handle(lock, &lockh);
                rc = ldlm_cli_cancel(&lockh, LCF_ASYNC);
                break;
        case LDLM_CB_CANCELING:
                /* We've given up the lock, prepare ourselves to update. */
                LDLM_DEBUG(lock, "MGC cancel CB");

                CDEBUG(D_MGC, "Lock res "DLDLMRES" (%.8s)\n",
                       PLDLMRES(lock->l_resource),
                       (char *)&lock->l_resource->lr_name.name[0]);

                if (!cld) {
                        CDEBUG(D_INFO, "missing data, won't requeue\n");
                        break;
                }

                /* held at mgc_process_log(). */
                LASSERT(atomic_read(&cld->cld_refcount) > 0);
                /* Are we done with this log? */
                if (cld->cld_stopping) {
                        CDEBUG(D_MGC, "log %s: stopping, won't requeue\n",
                               cld->cld_logname);
                        config_log_put(cld);
                        break;
                }
                /* Make sure not to re-enqueue when the mgc is stopping
                 * (we get called from client_disconnect_export)
                 */
                if (!lock->l_conn_export ||
                    !lock->l_conn_export->exp_obd->u.cli.cl_conn_count) {
                        CDEBUG(D_MGC, "log %.8s: disconnecting, won't requeue\n",
                               cld->cld_logname);
                        config_log_put(cld);
                        break;
                }

                /* Re-enqueue now */
                mgc_requeue_add(cld);
                config_log_put(cld);
                break;
        default:
                LBUG();
        }

        return rc;
}

/* Not sure where this should go... */
/* This is the timeout value for MGS_CONNECT request plus a ping interval, such
 * that we can have a chance to try the secondary MGS if any.
 */
#define  MGC_ENQUEUE_LIMIT (INITIAL_CONNECT_TIMEOUT + (AT_OFF ? 0 : at_min) \
                                + PING_INTERVAL)
#define  MGC_TARGET_REG_LIMIT 10
#define  MGC_SEND_PARAM_LIMIT 10

/* Send parameter to MGS*/
static int mgc_set_mgs_param(struct obd_export *exp,
                             struct mgs_send_param *msp)
{
        struct ptlrpc_request *req;
        struct mgs_send_param *req_msp, *rep_msp;
        int rc;

        req = ptlrpc_request_alloc_pack(class_exp2cliimp(exp),
                                        &RQF_MGS_SET_INFO, LUSTRE_MGS_VERSION,
                                        MGS_SET_INFO);
        if (!req)
                return -ENOMEM;

        req_msp = req_capsule_client_get(&req->rq_pill, &RMF_MGS_SEND_PARAM);
        if (!req_msp) {
                ptlrpc_req_finished(req);
                return -ENOMEM;
        }

        memcpy(req_msp, msp, sizeof(*req_msp));
        ptlrpc_request_set_replen(req);

        /* Limit how long we will wait for the enqueue to complete */
        req->rq_delay_limit = MGC_SEND_PARAM_LIMIT;
        rc = ptlrpc_queue_wait(req);
        if (!rc) {
                rep_msp = req_capsule_server_get(&req->rq_pill, &RMF_MGS_SEND_PARAM);
                memcpy(msp, rep_msp, sizeof(*rep_msp));
        }

        ptlrpc_req_finished(req);

        return rc;
}

/* Take a config lock so we can get cancel notifications */
static int mgc_enqueue(struct obd_export *exp, struct lov_stripe_md *lsm,
                       __u32 type, ldlm_policy_data_t *policy, __u32 mode,
                       __u64 *flags, void *bl_cb, void *cp_cb, void *gl_cb,
                       void *data, __u32 lvb_len, void *lvb_swabber,
                       struct lustre_handle *lockh)
{
        struct config_llog_data *cld = data;
        struct ldlm_enqueue_info einfo = {
                .ei_type        = type,
                .ei_mode        = mode,
                .ei_cb_bl       = mgc_blocking_ast,
                .ei_cb_cp       = ldlm_completion_ast,
        };
        struct ptlrpc_request *req;
        int short_limit = cld_is_sptlrpc(cld);
        int rc;

        CDEBUG(D_MGC, "Enqueue for %s (res %#llx)\n", cld->cld_logname,
               cld->cld_resid.name[0]);

        /* We need a callback for every lockholder, so don't try to
         * ldlm_lock_match (see rev 1.1.2.11.2.47)
         */
        req = ptlrpc_request_alloc_pack(class_exp2cliimp(exp),
                                        &RQF_LDLM_ENQUEUE, LUSTRE_DLM_VERSION,
                                        LDLM_ENQUEUE);
        if (!req)
                return -ENOMEM;

        req_capsule_set_size(&req->rq_pill, &RMF_DLM_LVB, RCL_SERVER, 0);
        ptlrpc_request_set_replen(req);

        /* Limit how long we will wait for the enqueue to complete */
        req->rq_delay_limit = short_limit ? 5 : MGC_ENQUEUE_LIMIT;
        rc = ldlm_cli_enqueue(exp, &req, &einfo, &cld->cld_resid, NULL, flags,
                              NULL, 0, LVB_T_NONE, lockh, 0);
        /* A failed enqueue should still call the mgc_blocking_ast,
         * where it will be requeued if needed ("grant failed").
         */
        ptlrpc_req_finished(req);
        return rc;
}

static void mgc_notify_active(struct obd_device *unused)
{
        /* wakeup mgc_requeue_thread to requeue mgc lock */
        spin_lock(&config_list_lock);
        rq_state |= RQ_NOW;
        spin_unlock(&config_list_lock);
        wake_up(&rq_waitq);

        /* TODO: Help the MGS rebuild nidtbl. -jay */
}

/* Send target_reg message to MGS */
static int mgc_target_register(struct obd_export *exp,
                               struct mgs_target_info *mti)
{
        struct ptlrpc_request  *req;
        struct mgs_target_info *req_mti, *rep_mti;
        int                  rc;

        req = ptlrpc_request_alloc_pack(class_exp2cliimp(exp),
                                        &RQF_MGS_TARGET_REG, LUSTRE_MGS_VERSION,
                                        MGS_TARGET_REG);
        if (!req)
                return -ENOMEM;

        req_mti = req_capsule_client_get(&req->rq_pill, &RMF_MGS_TARGET_INFO);
        if (!req_mti) {
                ptlrpc_req_finished(req);
                return -ENOMEM;
        }

        memcpy(req_mti, mti, sizeof(*req_mti));
        ptlrpc_request_set_replen(req);
        CDEBUG(D_MGC, "register %s\n", mti->mti_svname);
        /* Limit how long we will wait for the enqueue to complete */
        req->rq_delay_limit = MGC_TARGET_REG_LIMIT;

        rc = ptlrpc_queue_wait(req);
        if (!rc) {
                rep_mti = req_capsule_server_get(&req->rq_pill,
                                                 &RMF_MGS_TARGET_INFO);
                memcpy(mti, rep_mti, sizeof(*rep_mti));
                CDEBUG(D_MGC, "register %s got index = %d\n",
                       mti->mti_svname, mti->mti_stripe_index);
        }
        ptlrpc_req_finished(req);

        return rc;
}

static int mgc_set_info_async(const struct lu_env *env, struct obd_export *exp,
                              u32 keylen, void *key, u32 vallen,
                              void *val, struct ptlrpc_request_set *set)
{
        int rc = -EINVAL;

        /* Turn off initial_recov after we try all backup servers once */
        if (KEY_IS(KEY_INIT_RECOV_BACKUP)) {
                struct obd_import *imp = class_exp2cliimp(exp);
                int value;

                if (vallen != sizeof(int))
                        return -EINVAL;
                value = *(int *)val;
                CDEBUG(D_MGC, "InitRecov %s %d/d%d:i%d:r%d:or%d:%s\n",
                       imp->imp_obd->obd_name, value,
                       imp->imp_deactive, imp->imp_invalid,
                       imp->imp_replayable, imp->imp_obd->obd_replayable,
                       ptlrpc_import_state_name(imp->imp_state));
                /* Resurrect if we previously died */
                if ((imp->imp_state != LUSTRE_IMP_FULL &&
                     imp->imp_state != LUSTRE_IMP_NEW) || value > 1)
                        ptlrpc_reconnect_import(imp);
                return 0;

        }
        if (KEY_IS(KEY_SET_INFO)) {
                struct mgs_send_param *msp;

                msp = val;
                rc =  mgc_set_mgs_param(exp, msp);
                return rc;
        }
        if (KEY_IS(KEY_MGSSEC)) {
                struct client_obd     *cli = &exp->exp_obd->u.cli;
                struct sptlrpc_flavor  flvr;

                /*
                 * empty string means using current flavor, if which haven't
                 * been set yet, set it as null.
                 *
                 * if flavor has been set previously, check the asking flavor
                 * must match the existing one.
                 */
                if (vallen == 0) {
                        if (cli->cl_flvr_mgc.sf_rpc != SPTLRPC_FLVR_INVALID)
                                return 0;
                        val = "null";
                        vallen = 4;
                }

                rc = sptlrpc_parse_flavor(val, &flvr);
                if (rc) {
                        CERROR("invalid sptlrpc flavor %s to MGS\n",
                               (char *) val);
                        return rc;
                }

                /*
                 * caller already hold a mutex
                 */
                if (cli->cl_flvr_mgc.sf_rpc == SPTLRPC_FLVR_INVALID) {
                        cli->cl_flvr_mgc = flvr;
                } else if (memcmp(&cli->cl_flvr_mgc, &flvr,
                                  sizeof(flvr)) != 0) {
                        char    str[20];

                        sptlrpc_flavor2name(&cli->cl_flvr_mgc,
                                            str, sizeof(str));
                        LCONSOLE_ERROR("asking sptlrpc flavor %s to MGS but currently %s is in use\n",
                                       (char *) val, str);
                        rc = -EPERM;
                }
                return rc;
        }

        return rc;
}

static int mgc_get_info(const struct lu_env *env, struct obd_export *exp,
                        __u32 keylen, void *key, __u32 *vallen, void *val,
                        struct lov_stripe_md *unused)
{
        int rc = -EINVAL;

        if (KEY_IS(KEY_CONN_DATA)) {
                struct obd_import *imp = class_exp2cliimp(exp);
                struct obd_connect_data *data = val;

                if (*vallen == sizeof(*data)) {
                        *data = imp->imp_connect_data;
                        rc = 0;
                }
        }

        return rc;
}

static int mgc_import_event(struct obd_device *obd,
                            struct obd_import *imp,
                            enum obd_import_event event)
{
        LASSERT(imp->imp_obd == obd);
        CDEBUG(D_MGC, "import event %#x\n", event);

        switch (event) {
        case IMP_EVENT_DISCON:
                /* MGC imports should not wait for recovery */
                if (OCD_HAS_FLAG(&imp->imp_connect_data, IMP_RECOV))
                        ptlrpc_pinger_ir_down();
                break;
        case IMP_EVENT_INACTIVE:
                break;
        case IMP_EVENT_INVALIDATE: {
                struct ldlm_namespace *ns = obd->obd_namespace;

                ldlm_namespace_cleanup(ns, LDLM_FL_LOCAL_ONLY);
                break;
        }
        case IMP_EVENT_ACTIVE:
                CDEBUG(D_INFO, "%s: Reactivating import\n", obd->obd_name);
                /* Clearing obd_no_recov allows us to continue pinging */
                obd->obd_no_recov = 0;
                mgc_notify_active(obd);
                if (OCD_HAS_FLAG(&imp->imp_connect_data, IMP_RECOV))
                        ptlrpc_pinger_ir_up();
                break;
        case IMP_EVENT_OCD:
                break;
        case IMP_EVENT_DEACTIVATE:
        case IMP_EVENT_ACTIVATE:
                break;
        default:
                CERROR("Unknown import event %#x\n", event);
                LBUG();
        }
        return 0;
}

enum {
        CONFIG_READ_NRPAGES_INIT = 1 << (20 - PAGE_SHIFT),
        CONFIG_READ_NRPAGES      = 4
};

static int mgc_apply_recover_logs(struct obd_device *mgc,
                                  struct config_llog_data *cld,
                                  __u64 max_version,
                                  void *data, int datalen, bool mne_swab)
{
        struct config_llog_instance *cfg = &cld->cld_cfg;
        struct mgs_nidtbl_entry *entry;
        struct lustre_cfg       *lcfg;
        struct lustre_cfg_bufs   bufs;
        u64   prev_version = 0;
        char *inst;
        char *buf;
        int   bufsz;
        int   pos;
        int   rc  = 0;
        int   off = 0;

        LASSERT(cfg->cfg_instance);
        LASSERT(cfg->cfg_sb == cfg->cfg_instance);

        inst = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!inst)
                return -ENOMEM;

        pos = snprintf(inst, PAGE_SIZE, "%p", cfg->cfg_instance);
        if (pos >= PAGE_SIZE) {
                kfree(inst);
                return -E2BIG;
        }

        ++pos;
        buf   = inst + pos;
        bufsz = PAGE_SIZE - pos;

        while (datalen > 0) {
                int   entry_len = sizeof(*entry);
                int   is_ost;
                struct obd_device *obd;
                char *obdname;
                char *cname;
                char *params;
                char *uuid;

                rc = -EINVAL;
                if (datalen < sizeof(*entry))
                        break;

                entry = (typeof(entry))(data + off);

                /* sanity check */
                if (entry->mne_nid_type != 0) /* only support type 0 for ipv4 */
                        break;
                if (entry->mne_nid_count == 0) /* at least one nid entry */
                        break;
                if (entry->mne_nid_size != sizeof(lnet_nid_t))
                        break;

                entry_len += entry->mne_nid_count * entry->mne_nid_size;
                if (datalen < entry_len) /* must have entry_len at least */
                        break;

                /* Keep this swab for normal mixed endian handling. LU-1644 */
                if (mne_swab)
                        lustre_swab_mgs_nidtbl_entry(entry);
                if (entry->mne_length > PAGE_SIZE) {
                        CERROR("MNE too large (%u)\n", entry->mne_length);
                        break;
                }

                if (entry->mne_length < entry_len)
                        break;

                off     += entry->mne_length;
                datalen -= entry->mne_length;
                if (datalen < 0)
                        break;

                if (entry->mne_version > max_version) {
                        CERROR("entry index(%lld) is over max_index(%lld)\n",
                               entry->mne_version, max_version);
                        break;
                }

                if (prev_version >= entry->mne_version) {
                        CERROR("index unsorted, prev %lld, now %lld\n",
                               prev_version, entry->mne_version);
                        break;
                }
                prev_version = entry->mne_version;

                /*
                 * Write a string with format "nid::instance" to
                 * lustre/<osc|mdc>/<target>-<osc|mdc>-<instance>/import.
                 */

                is_ost = entry->mne_type == LDD_F_SV_TYPE_OST;
                memset(buf, 0, bufsz);
                obdname = buf;
                pos = 0;

                /* lustre-OST0001-osc-<instance #> */
                strcpy(obdname, cld->cld_logname);
                cname = strrchr(obdname, '-');
                if (!cname) {
                        CERROR("mgc %s: invalid logname %s\n",
                               mgc->obd_name, obdname);
                        break;
                }

                pos = cname - obdname;
                obdname[pos] = 0;
                pos += sprintf(obdname + pos, "-%s%04x",
                                  is_ost ? "OST" : "MDT", entry->mne_index);

                cname = is_ost ? "osc" : "mdc";
                pos += sprintf(obdname + pos, "-%s-%s", cname, inst);
                lustre_cfg_bufs_reset(&bufs, obdname);

                /* find the obd by obdname */
                obd = class_name2obd(obdname);
                if (!obd) {
                        CDEBUG(D_INFO, "mgc %s: cannot find obdname %s\n",
                               mgc->obd_name, obdname);
                        rc = 0;
                        /* this is a safe race, when the ost is starting up...*/
                        continue;
                }

                /* osc.import = "connection=<Conn UUID>::<target instance>" */
                ++pos;
                params = buf + pos;
                pos += sprintf(params, "%s.import=%s", cname, "connection=");
                uuid = buf + pos;

                down_read(&obd->u.cli.cl_sem);
                if (!obd->u.cli.cl_import) {
                        /* client does not connect to the OST yet */
                        up_read(&obd->u.cli.cl_sem);
                        rc = 0;
                        continue;
                }

                /* TODO: iterate all nids to find one */
                /* find uuid by nid */
                rc = client_import_find_conn(obd->u.cli.cl_import,
                                             entry->u.nids[0],
                                             (struct obd_uuid *)uuid);
                up_read(&obd->u.cli.cl_sem);
                if (rc < 0) {
                        CERROR("mgc: cannot find uuid by nid %s\n",
                               libcfs_nid2str(entry->u.nids[0]));
                        break;
                }

                CDEBUG(D_INFO, "Find uuid %s by nid %s\n",
                       uuid, libcfs_nid2str(entry->u.nids[0]));

                pos += strlen(uuid);
                pos += sprintf(buf + pos, "::%u", entry->mne_instance);
                LASSERT(pos < bufsz);

                lustre_cfg_bufs_set_string(&bufs, 1, params);

                rc = -ENOMEM;
                lcfg = lustre_cfg_new(LCFG_PARAM, &bufs);
                if (IS_ERR(lcfg)) {
                        CERROR("mgc: cannot allocate memory\n");
                        break;
                }

                CDEBUG(D_INFO, "ir apply logs %lld/%lld for %s -> %s\n",
                       prev_version, max_version, obdname, params);

                rc = class_process_config(lcfg);
                lustre_cfg_free(lcfg);
                if (rc)
                        CDEBUG(D_INFO, "process config for %s error %d\n",
                               obdname, rc);

                /* continue, even one with error */
        }

        kfree(inst);
        return rc;
}

/**
 * This function is called if this client was notified for target restarting
 * by the MGS. A CONFIG_READ RPC is going to send to fetch recovery logs.
 */
static int mgc_process_recover_log(struct obd_device *obd,
                                   struct config_llog_data *cld)
{
        struct ptlrpc_request *req = NULL;
        struct config_llog_instance *cfg = &cld->cld_cfg;
        struct mgs_config_body *body;
        struct mgs_config_res  *res;
        struct ptlrpc_bulk_desc *desc;
        struct page **pages;
        int nrpages;
        bool eof = true;
        bool mne_swab;
        int i;
        int ealen;
        int rc;

        /* allocate buffer for bulk transfer.
         * if this is the first time for this mgs to read logs,
         * CONFIG_READ_NRPAGES_INIT will be used since it will read all logs
         * once; otherwise, it only reads increment of logs, this should be
         * small and CONFIG_READ_NRPAGES will be used.
         */
        nrpages = CONFIG_READ_NRPAGES;
        if (cfg->cfg_last_idx == 0) /* the first time */
                nrpages = CONFIG_READ_NRPAGES_INIT;

        pages = kcalloc(nrpages, sizeof(*pages), GFP_KERNEL);
        if (!pages) {
                rc = -ENOMEM;
                goto out;
        }

        for (i = 0; i < nrpages; i++) {
                pages[i] = alloc_page(GFP_KERNEL);
                if (!pages[i]) {
                        rc = -ENOMEM;
                        goto out;
                }
        }

again:
        LASSERT(cld_is_recover(cld));
        LASSERT(mutex_is_locked(&cld->cld_lock));
        req = ptlrpc_request_alloc(class_exp2cliimp(cld->cld_mgcexp),
                                   &RQF_MGS_CONFIG_READ);
        if (!req) {
                rc = -ENOMEM;
                goto out;
        }

        rc = ptlrpc_request_pack(req, LUSTRE_MGS_VERSION, MGS_CONFIG_READ);
        if (rc)
                goto out;

        /* pack request */
        body = req_capsule_client_get(&req->rq_pill, &RMF_MGS_CONFIG_BODY);
        LASSERT(sizeof(body->mcb_name) > strlen(cld->cld_logname));
        if (strlcpy(body->mcb_name, cld->cld_logname, sizeof(body->mcb_name))
            >= sizeof(body->mcb_name)) {
                rc = -E2BIG;
                goto out;
        }
        body->mcb_offset = cfg->cfg_last_idx + 1;
        body->mcb_type   = cld->cld_type;
        body->mcb_bits   = PAGE_SHIFT;
        body->mcb_units  = nrpages;

        /* allocate bulk transfer descriptor */
        desc = ptlrpc_prep_bulk_imp(req, nrpages, 1, BULK_PUT_SINK,
                                    MGS_BULK_PORTAL);
        if (!desc) {
                rc = -ENOMEM;
                goto out;
        }

        for (i = 0; i < nrpages; i++)
                ptlrpc_prep_bulk_page_pin(desc, pages[i], 0, PAGE_SIZE);

        ptlrpc_request_set_replen(req);
        rc = ptlrpc_queue_wait(req);
        if (rc)
                goto out;

        res = req_capsule_server_get(&req->rq_pill, &RMF_MGS_CONFIG_RES);
        if (res->mcr_size < res->mcr_offset) {
                rc = -EINVAL;
                goto out;
        }

        /* always update the index even though it might have errors with
         * handling the recover logs
         */
        cfg->cfg_last_idx = res->mcr_offset;
        eof = res->mcr_offset == res->mcr_size;

        CDEBUG(D_INFO, "Latest version %lld, more %d.\n",
               res->mcr_offset, eof == false);

        ealen = sptlrpc_cli_unwrap_bulk_read(req, req->rq_bulk, 0);
        if (ealen < 0) {
                rc = ealen;
                goto out;
        }

        if (ealen > nrpages << PAGE_SHIFT) {
                rc = -EINVAL;
                goto out;
        }

        if (ealen == 0) { /* no logs transferred */
                if (!eof)
                        rc = -EINVAL;
                goto out;
        }

        mne_swab = !!ptlrpc_rep_need_swab(req);
#if LUSTRE_VERSION_CODE < OBD_OCD_VERSION(3, 2, 50, 0)
        /* This import flag means the server did an extra swab of IR MNE
         * records (fixed in LU-1252), reverse it here if needed. LU-1644
         */
        if (unlikely(req->rq_import->imp_need_mne_swab))
                mne_swab = !mne_swab;
#else
#warning "LU-1644: Remove old OBD_CONNECT_MNE_SWAB fixup and imp_need_mne_swab"
#endif

        for (i = 0; i < nrpages && ealen > 0; i++) {
                int rc2;
                void *ptr;

                ptr = kmap(pages[i]);
                rc2 = mgc_apply_recover_logs(obd, cld, res->mcr_offset, ptr,
                                             min_t(int, ealen, PAGE_SIZE),
                                             mne_swab);
                kunmap(pages[i]);
                if (rc2 < 0) {
                        CWARN("Process recover log %s error %d\n",
                              cld->cld_logname, rc2);
                        break;
                }

                ealen -= PAGE_SIZE;
        }

out:
        if (req)
                ptlrpc_req_finished(req);

        if (rc == 0 && !eof)
                goto again;

        if (pages) {
                for (i = 0; i < nrpages; i++) {
                        if (!pages[i])
                                break;
                        __free_page(pages[i]);
                }
                kfree(pages);
        }
        return rc;
}

/* local_only means it cannot get remote llogs */
static int mgc_process_cfg_log(struct obd_device *mgc,
                               struct config_llog_data *cld, int local_only)
{
        struct llog_ctxt        *ctxt;
        struct lustre_sb_info   *lsi = NULL;
        int                      rc = 0;
        bool                     sptlrpc_started = false;
        struct lu_env           *env;

        LASSERT(cld);
        LASSERT(mutex_is_locked(&cld->cld_lock));

        /*
         * local copy of sptlrpc log is controlled elsewhere, don't try to
         * read it up here.
         */
        if (cld_is_sptlrpc(cld) && local_only)
                return 0;

        if (cld->cld_cfg.cfg_sb)
                lsi = s2lsi(cld->cld_cfg.cfg_sb);

        env = kzalloc(sizeof(*env), GFP_KERNEL);
        if (!env)
                return -ENOMEM;

        rc = lu_env_init(env, LCT_MG_THREAD);
        if (rc)
                goto out_free;

        ctxt = llog_get_context(mgc, LLOG_CONFIG_REPL_CTXT);
        LASSERT(ctxt);

        if (local_only) /* no local log at client side */ {
                rc = -EIO;
                goto out_pop;
        }

        if (cld_is_sptlrpc(cld)) {
                sptlrpc_conf_log_update_begin(cld->cld_logname);
                sptlrpc_started = true;
        }

        /* logname and instance info should be the same, so use our
         * copy of the instance for the update.  The cfg_last_idx will
         * be updated here.
         */
        rc = class_config_parse_llog(env, ctxt, cld->cld_logname,
                                     &cld->cld_cfg);

out_pop:
        __llog_ctxt_put(env, ctxt);

        /*
         * update settings on existing OBDs. doing it inside
         * of llog_process_lock so no device is attaching/detaching
         * in parallel.
         * the logname must be <fsname>-sptlrpc
         */
        if (sptlrpc_started) {
                LASSERT(cld_is_sptlrpc(cld));
                sptlrpc_conf_log_update_end(cld->cld_logname);
                class_notify_sptlrpc_conf(cld->cld_logname,
                                          strlen(cld->cld_logname) -
                                          strlen("-sptlrpc"));
        }

        lu_env_fini(env);
out_free:
        kfree(env);
        return rc;
}

/** Get a config log from the MGS and process it.
 * This func is called for both clients and servers.
 * Copy the log locally before parsing it if appropriate (non-MGS server)
 */
int mgc_process_log(struct obd_device *mgc, struct config_llog_data *cld)
{
        struct lustre_handle lockh = { 0 };
        __u64 flags = LDLM_FL_NO_LRU;
        int rc = 0, rcl;

        LASSERT(cld);

        /* I don't want multiple processes running process_log at once --
         * sounds like badness.  It actually might be fine, as long as
         * we're not trying to update from the same log
         * simultaneously (in which case we should use a per-log sem.)
         */
        mutex_lock(&cld->cld_lock);
        if (cld->cld_stopping) {
                mutex_unlock(&cld->cld_lock);
                return 0;
        }

        OBD_FAIL_TIMEOUT(OBD_FAIL_MGC_PAUSE_PROCESS_LOG, 20);

        CDEBUG(D_MGC, "Process log %s:%p from %d\n", cld->cld_logname,
               cld->cld_cfg.cfg_instance, cld->cld_cfg.cfg_last_idx + 1);

        /* Get the cfg lock on the llog */
        rcl = mgc_enqueue(mgc->u.cli.cl_mgc_mgsexp, NULL, LDLM_PLAIN, NULL,
                          LCK_CR, &flags, NULL, NULL, NULL,
                          cld, 0, NULL, &lockh);
        if (rcl == 0) {
                /* Get the cld, it will be released in mgc_blocking_ast. */
                config_log_get(cld);
                rc = ldlm_lock_set_data(&lockh, (void *)cld);
                LASSERT(rc == 0);
        } else {
                CDEBUG(D_MGC, "Can't get cfg lock: %d\n", rcl);

                /* mark cld_lostlock so that it will requeue
                 * after MGC becomes available.
                 */
                cld->cld_lostlock = 1;
                /* Get extra reference, it will be put in requeue thread */
                config_log_get(cld);
        }

        if (cld_is_recover(cld)) {
                rc = 0; /* this is not a fatal error for recover log */
                if (rcl == 0)
                        rc = mgc_process_recover_log(mgc, cld);
        } else {
                rc = mgc_process_cfg_log(mgc, cld, rcl != 0);
        }

        CDEBUG(D_MGC, "%s: configuration from log '%s' %sed (%d).\n",
               mgc->obd_name, cld->cld_logname, rc ? "fail" : "succeed", rc);

        mutex_unlock(&cld->cld_lock);

        /* Now drop the lock so MGS can revoke it */
        if (!rcl)
                ldlm_lock_decref(&lockh, LCK_CR);

        return rc;
}

/** Called from lustre_process_log.
 * LCFG_LOG_START gets the config log from the MGS, processes it to start
 * any services, and adds it to the list logs to watch (follow).
 */
static int mgc_process_config(struct obd_device *obd, u32 len, void *buf)
{
        struct lustre_cfg *lcfg = buf;
        struct config_llog_instance *cfg = NULL;
        char *logname;
        int rc = 0;

        switch (lcfg->lcfg_command) {
        case LCFG_LOV_ADD_OBD: {
                /* Overloading this cfg command: register a new target */
                struct mgs_target_info *mti;

                if (LUSTRE_CFG_BUFLEN(lcfg, 1) !=
                    sizeof(struct mgs_target_info)) {
                        rc = -EINVAL;
                        goto out;
                }

                mti = (struct mgs_target_info *)lustre_cfg_buf(lcfg, 1);
                CDEBUG(D_MGC, "add_target %s %#x\n",
                       mti->mti_svname, mti->mti_flags);
                rc = mgc_target_register(obd->u.cli.cl_mgc_mgsexp, mti);
                break;
        }
        case LCFG_LOV_DEL_OBD:
                /* Unregister has no meaning at the moment. */
                CERROR("lov_del_obd unimplemented\n");
                rc = -ENOSYS;
                break;
        case LCFG_SPTLRPC_CONF: {
                rc = sptlrpc_process_config(lcfg);
                break;
        }
        case LCFG_LOG_START: {
                struct config_llog_data *cld;
                struct super_block *sb;

                logname = lustre_cfg_string(lcfg, 1);
                cfg = (struct config_llog_instance *)lustre_cfg_buf(lcfg, 2);
                sb = *(struct super_block **)lustre_cfg_buf(lcfg, 3);

                CDEBUG(D_MGC, "parse_log %s from %d\n", logname,
                       cfg->cfg_last_idx);

                /* We're only called through here on the initial mount */
                rc = config_log_add(obd, logname, cfg, sb);
                if (rc)
                        break;
                cld = config_log_find(logname, cfg);
                if (!cld) {
                        rc = -ENOENT;
                        break;
                }

                /* COMPAT_146 */
                /* FIXME only set this for old logs!  Right now this forces
                 * us to always skip the "inside markers" check
                 */
                cld->cld_cfg.cfg_flags |= CFG_F_COMPAT146;

                rc = mgc_process_log(obd, cld);
                if (rc == 0 && cld->cld_recover) {
                        if (OCD_HAS_FLAG(&obd->u.cli.cl_import->
                                         imp_connect_data, IMP_RECOV)) {
                                rc = mgc_process_log(obd, cld->cld_recover);
                        } else {
                                struct config_llog_data *cir = cld->cld_recover;

                                cld->cld_recover = NULL;
                                config_log_put(cir);
                        }
                        if (rc)
                                CERROR("Cannot process recover llog %d\n", rc);
                }

                if (rc == 0 && cld->cld_params) {
                        rc = mgc_process_log(obd, cld->cld_params);
                        if (rc == -ENOENT) {
                                CDEBUG(D_MGC,
                                       "There is no params config file yet\n");
                                rc = 0;
                        }
                        /* params log is optional */
                        if (rc)
                                CERROR(
                                       "%s: can't process params llog: rc = %d\n",
                                       obd->obd_name, rc);
                }
                config_log_put(cld);

                break;
        }
        case LCFG_LOG_END: {
                logname = lustre_cfg_string(lcfg, 1);

                if (lcfg->lcfg_bufcount >= 2)
                        cfg = (struct config_llog_instance *)lustre_cfg_buf(
                                lcfg, 2);
                rc = config_log_end(logname, cfg);
                break;
        }
        default: {
                CERROR("Unknown command: %d\n", lcfg->lcfg_command);
                rc = -EINVAL;
                goto out;

        }
        }
out:
        return rc;
}

static struct obd_ops mgc_obd_ops = {
        .owner          = THIS_MODULE,
        .setup          = mgc_setup,
        .precleanup     = mgc_precleanup,
        .cleanup        = mgc_cleanup,
        .add_conn       = client_import_add_conn,
        .del_conn       = client_import_del_conn,
        .connect        = client_connect_import,
        .disconnect     = client_disconnect_export,
        /* .enqueue     = mgc_enqueue, */
        /* .iocontrol   = mgc_iocontrol, */
        .set_info_async = mgc_set_info_async,
        .get_info       = mgc_get_info,
        .import_event   = mgc_import_event,
        .process_config = mgc_process_config,
};

static int __init mgc_init(void)
{
        return class_register_type(&mgc_obd_ops, NULL,
                                   LUSTRE_MGC_NAME, NULL);
}

static void /*__exit*/ mgc_exit(void)
{
        class_unregister_type(LUSTRE_MGC_NAME);
}

MODULE_AUTHOR("OpenSFS, Inc. <http://www.lustre.org/>");
MODULE_DESCRIPTION("Lustre Management Client");
MODULE_VERSION(LUSTRE_VERSION_STRING);
MODULE_LICENSE("GPL");

module_init(mgc_init);
module_exit(mgc_exit);