graphene/LibOS/shim/src/sys/shim_msgget.c

/* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
/* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */

/* Copyright (C) 2014 OSCAR lab, Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * shim_msgget.c
 *
 * Implementation of system call "msgget", "msgsnd", "msgrcv" and "msgctl".
 */

#include <shim_internal.h>
#include <shim_handle.h>
#include <shim_utils.h>
#include <shim_ipc.h>
#include <shim_sysv.h>
#include <shim_unistd.h>
#include <shim_profile.h>

#include <pal.h>
#include <pal_error.h>
#include <linux_list.h>
#include <errno.h>

#define MSGQ_HASH_LEN     8
#define MSGQ_HASH_NUM     (1 << MSGQ_HASH_LEN)
#define MSGQ_HASH_MASK    (MSGQ_HASH_NUM - 1)
#define MSGQ_HASH(idx)    ((idx) & MSGQ_HASH_MASK)

static LIST_HEAD(msgq_list);
static struct hlist_head msgq_key_hlist [MSGQ_HASH_NUM];
static struct hlist_head msgq_qid_hlist [MSGQ_HASH_NUM];
static LOCKTYPE msgq_list_lock;

static int __load_msg_persist (struct shim_msg_handle * msgq, bool readmsg);
static int __store_msg_persist(struct shim_msg_handle * msgq);

DEFINE_PROFILE_CATAGORY(sysv_msg, );

#define MSG_TO_HANDLE(msghdl)   \
        container_of((msghdl), struct shim_handle, info.msg)

static int __add_msg_handle (unsigned long key, IDTYPE msqid, bool owned,
                             struct shim_msg_handle ** msghdl)
{
    struct hlist_head * key_head = (key != IPC_PRIVATE) ?
                                   &msgq_key_hlist[MSGQ_HASH(key)] :
                                   NULL;
    struct hlist_head * qid_head = msqid ?
                                   &msgq_qid_hlist[MSGQ_HASH(msqid)] :
                                   NULL;

    struct shim_msg_handle * tmp;
    struct hlist_node * pos;

    if (key_head)
        hlist_for_each_entry(tmp, pos, key_head, key_hlist)
            if (tmp->msqkey == key) {
                if (tmp->msqid == msqid) {
                    if (msghdl)
                        *msghdl = tmp;
                    return 0;
                }
                return -EEXIST;
            }

    if (qid_head)
        hlist_for_each_entry(tmp, pos, qid_head, qid_hlist)
            if (tmp->msqid == msqid) {
                if (key)
                    tmp->msqkey = key;
                if (msghdl)
                    *msghdl = tmp;
                return 0;
            }

    struct shim_handle * hdl = get_new_handle();
    if (!hdl)
        return -ENOMEM;

    struct shim_msg_handle * msgq = &hdl->info.msg;

    hdl->type       = TYPE_MSG;
    msgq->msqkey    = key;
    msgq->msqid     = msqid;
    msgq->owned     = owned;
    msgq->deleted   = false;
    msgq->currentsize = 0;
    msgq->event     = DkSynchronizationEventCreate(0);

    msgq->queue     = malloc(MSG_QOBJ_SIZE * DEFAULT_MSG_QUEUE_SIZE);
    msgq->queuesize = DEFAULT_MSG_QUEUE_SIZE;
    msgq->queueused = 0;
    msgq->freed     = NULL;

    msgq->ntypes    = 0;
    msgq->maxtypes  = INIT_MSG_TYPE_SIZE;
    msgq->types     = malloc(sizeof(struct msg_type) * INIT_MSG_TYPE_SIZE);

    INIT_LIST_HEAD(&msgq->list);
    get_handle(hdl);
    list_add_tail(&msgq->list, &msgq_list);

    INIT_HLIST_NODE(&msgq->key_hlist);
    if (key_head) {
        get_handle(hdl);
        hlist_add_head(&msgq->key_hlist, key_head);
    }
    INIT_HLIST_NODE(&msgq->qid_hlist);
    if (qid_head) {
        get_handle(hdl);
        hlist_add_head(&msgq->qid_hlist, qid_head);
    }

    if (!msghdl) {
        put_handle(hdl);
        return 0;
    }

    *msghdl = msgq;
    return 0;
}

int add_msg_handle (unsigned long key, IDTYPE id, bool owned)
{
    lock(msgq_list_lock);
    int ret = __add_msg_handle(key, id, owned, NULL);
    unlock(msgq_list_lock);
    return ret;
}

struct shim_msg_handle * get_msg_handle_by_key (unsigned long key)
{

    struct hlist_head * key_head = &msgq_key_hlist[MSGQ_HASH(key)];
    struct shim_msg_handle * tmp, * found = NULL;
    struct hlist_node * pos;

    lock(msgq_list_lock);

    hlist_for_each_entry(tmp, pos, key_head, key_hlist)
        if (tmp->msqkey == key) {
            found = tmp;
            break;
        }

    if (found)
        get_handle(MSG_TO_HANDLE(found));

    unlock(msgq_list_lock);
    return found;
}

struct shim_msg_handle * get_msg_handle_by_id (IDTYPE msqid)
{
    struct hlist_head * qid_head = &msgq_qid_hlist[MSGQ_HASH(msqid)];
    struct shim_msg_handle * tmp, * found = NULL;
    struct hlist_node * pos;

    lock(msgq_list_lock);

    hlist_for_each_entry(tmp, pos, qid_head, qid_hlist)
        if (tmp->msqid == msqid) {
            found = tmp;
            break;
        }

    if (found)
        get_handle(MSG_TO_HANDLE(found));

    unlock(msgq_list_lock);
    return found;
}

void put_msg_handle (struct shim_msg_handle * msgq)
{
    put_handle(MSG_TO_HANDLE(msgq));
}

static void * __get_msg_qobj (struct shim_msg_handle * msgq)
{
    struct msg_qobj * obj = NULL;

    if (msgq->freed) {
        obj = msgq->freed;
        msgq->freed = obj->next;
        obj->next = NULL;
        return obj;
    }

    if (msgq->queueused < msgq->queuesize) {
        obj = &msgq->queue[msgq->queueused];
        msgq->queueused++;
        obj->next = NULL;
        return obj;
    }

    return NULL;
}

static void __free_msg_qobj (struct shim_msg_handle * msgq, void * obj)
{
    ((struct msg_qobj *) obj)->next = msgq->freed;
    msgq->freed = obj;
}

static void __free_msg_linked_qobjs (struct shim_msg_handle * msgq, void * obj)
{
    struct msg_qobj * qobj = obj;
    while (qobj) {
        struct msg_qobj * next = qobj->next;
        __free_msg_qobj(msgq, qobj);
        qobj = next;
    }
}

static int __del_msg_handle (struct shim_msg_handle * msgq)
{
    if (msgq->deleted)
        return -EIDRM;

    msgq->deleted = true;
    free(msgq->queue);
    msgq->queuesize = 0;
    msgq->queueused = 0;
    free(msgq->types);
    msgq->ntypes = 0;

    struct shim_handle * hdl = MSG_TO_HANDLE(msgq);

    lock(msgq_list_lock);
    list_del_init(&msgq->list);
    put_handle(hdl);
    if (!hlist_unhashed(&msgq->key_hlist)) {
        hlist_del_init(&msgq->key_hlist);
        put_handle(hdl);
    }
    if (!hlist_unhashed(&msgq->qid_hlist)) {
        hlist_del_init(&msgq->qid_hlist);
        put_handle(hdl);
    }
    unlock(msgq_list_lock);
    return 0;
}

int del_msg_handle (struct shim_msg_handle * msgq)
{
    struct shim_handle * hdl = MSG_TO_HANDLE(msgq);
    lock(hdl->lock);
    int ret = __del_msg_handle(msgq);
    unlock(hdl->lock);
    return ret;
}

static void __try_create_lock (void)
{
    create_lock_runtime(&msgq_list_lock);
}

int shim_do_msgget (key_t key, int msgflg)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);
    IDTYPE msgid = 0;
    int ret;
    __try_create_lock();

    if (key != IPC_PRIVATE) {
        struct shim_msg_handle * msgq = get_msg_handle_by_key(key);
        if (msgq) {
            msgid = msgq->msqid;
            put_msg_handle(msgq);
            return (msgflg & IPC_EXCL) ? -EEXIST : msgid;
        }
    }

    struct sysv_key k;
    k.key  = key;
    k.type = SYSV_MSGQ;

    if (msgflg & IPC_CREAT) {
        do {
            msgid = allocate_sysv(0, 0);
            if (!msgid)
                ipc_sysv_lease_send(NULL);
        } while (!msgid);

        if (key != IPC_PRIVATE) {
            if ((ret = ipc_sysv_tellkey_send(NULL, 0, &k, msgid, 0)) < 0) {
                release_sysv(msgid);
                return ret;
            }
        }

        add_msg_handle(key, msgid, true);
    } else {
        /* query the manager with the key to find the
           corresponding sysvkey */
        if ((ret = ipc_sysv_findkey_send(&k)) < 0)
            return ret;

        msgid = ret;

        if ((ret = ipc_sysv_query_send(msgid)) < 0)
            return ret;

        add_msg_handle(key, msgid, false);
    }

    return msgid;
}

static int connect_msg_handle (int msqid, struct shim_msg_handle ** msgqp)
{
    struct shim_msg_handle * msgq = get_msg_handle_by_id(msqid);
    int ret;

    if (!msgq) {
        if ((ret = ipc_sysv_query_send(msqid)) < 0)
            return ret;

        if (!msgq) {
            lock(msgq_list_lock);
            ret = __add_msg_handle(IPC_PRIVATE, msqid, false, &msgq);
            unlock(msgq_list_lock);
            if (ret < 0)
                return ret;
        }
    }

    if (msgq->deleted)
        return -EIDRM;

    *msgqp = msgq;
    return 0;
}

int recover_msg_ownership (struct shim_msg_handle * msgq)
{
    struct shim_handle * hdl = MSG_TO_HANDLE(msgq);
    lock(hdl->lock);
    assert(!msgq->owned);
    int ret = __load_msg_persist(msgq, true);

    if (ret < 0) {
        ret = (ret == -ENOENT) ? -EIDRM : ret;
        goto out;
    }

    msgq->owned = true;
    DkEventSet(msgq->event);
out:
    unlock(hdl->lock);
    return 0;
}

int shim_do_msgsnd (int msqid, const void * msgp, size_t msgsz, int msgflg)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);
    int ret;

    if ((msgsz < 0) || (msgsz > MSGMAX))
        return -EINVAL;

    if (!msgp)
        return -EFAULT;

    struct __kernel_msgbuf * msgbuf = (struct __kernel_msgbuf *) msgp;

    if (msgbuf->mtype < 0)
        return -EINVAL;

    struct shim_msg_handle * msgq;
    __try_create_lock();

    if ((ret = connect_msg_handle(msqid, &msgq)) < 0)
        return ret;

    ret = add_sysv_msg(msgq, msgbuf->mtype, msgsz, msgbuf->mtext, NULL);
    put_msg_handle(msgq);
    return ret;
}

int shim_do_msgrcv (int msqid, void * msgp, size_t msgsz, long msgtype,
                    int msgflg)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);
    int ret;

    if (msgsz < 0)
        return -EINVAL;
    if (!msgp)
        return -EFAULT;

    struct __kernel_msgbuf * msgbuf = (struct __kernel_msgbuf *) msgp;
    struct shim_msg_handle * msgq;
    __try_create_lock();

    if ((ret = connect_msg_handle(msqid, &msgq)) < 0)
        return ret;

    ret = get_sysv_msg(msgq, msgtype, msgsz, msgbuf->mtext, msgflg, NULL);
    put_msg_handle(msgq);
    return ret;
}

int shim_do_msgctl (int msqid, int cmd, struct msqid_ds * buf)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);
    struct shim_msg_handle * msgq;
    int ret;
    __try_create_lock();

    if ((ret = connect_msg_handle(msqid, &msgq)) < 0)
       return ret;

    switch (cmd) {
        case IPC_RMID:
            if (!msgq->owned) {
                ret = ipc_sysv_delres_send(NULL, 0, msgq->msqid, SYSV_MSGQ);
                if (ret < 0)
                    break;
            }

            __del_msg_handle(msgq);
            break;

        default:
            ret = -ENOSYS;
            break;
    }

    put_msg_handle(msgq);
    return ret;
}

static struct msg_type *
__add_msg_type (int type, struct msg_type ** ptypes, int * pntypes,
                int * pmaxtypes)
{
    struct msg_type * types = *ptypes;
    int ntypes = *pntypes;
    int maxtypes = *pmaxtypes;

    struct msg_type * mtype;
    for (mtype = types ;
         mtype < &types[ntypes] && mtype->type <= type ; mtype++)
        if (mtype->type == type)
            return mtype;

    int off = mtype - types;
    struct msg_type * new_types = types;

    if (ntypes == maxtypes)
        new_types = malloc(sizeof(struct msg_type) * maxtypes * 2);

    if (mtype < &types[ntypes])
        memmove(new_types + off + 1, mtype,
                sizeof(struct msg_type) * (ntypes - off));

    if (new_types != types) {
        memcpy(new_types, types, sizeof(struct msg_type) * off);
        free(types);
        mtype = new_types + off;
        *ptypes = new_types;
        *pmaxtypes = maxtypes * 2;
    }

    mtype->type = type;
    mtype->msgs = NULL;
    mtype->msg_tail = NULL;
    mtype->reqs = NULL;
    mtype->req_tail = NULL;

    (*pntypes)++;
    return mtype;
}

static int __load_msg_qobjs (struct shim_msg_handle * msgq,
                             struct msg_type * mtype,
                             struct msg_item * msg, void * data)
{
    int copysize = MSG_ITEM_DATA_SIZE(msg->size);
    memcpy(data, msg->data, copysize);
    mtype->msgs = msg->next;
    __free_msg_qobj(msgq, msg);

    while (copysize < msg->size) {
        assert(mtype->msgs);
        struct msg_ext_item * ext = (struct msg_ext_item *) mtype->msgs;
        int sz = MSG_EXT_ITEM_DATA_SIZE(msg->size - copysize);
        memcpy(data + copysize, ext->data, sz);
        copysize += sz;
        mtype->msgs = ext->next;
        __free_msg_qobj(msgq, ext);
    }

    if (!mtype->msgs)
        mtype->msg_tail = NULL;

    msgq->nmsgs--;
    msgq->currentsize -= msg->size;
    return 0;
}

static int __store_msg_qobjs (struct shim_msg_handle * msgq,
                              struct msg_type * mtype,
                              int size, const void * data)
{
    struct msg_item * newmsg = __get_msg_qobj(msgq);
    if (!newmsg)
        return -EAGAIN;

    struct msg_item * old_tail = mtype->msg_tail;

    newmsg->next = NULL;
    newmsg->size = size;
    int copysize = MSG_ITEM_DATA_SIZE(size);
    memcpy(newmsg->data, data, copysize);

    if (mtype->msg_tail) {
        mtype->msg_tail->next = newmsg;
        mtype->msg_tail = newmsg;
    } else {
        assert(!mtype->msgs);
        mtype->msgs = mtype->msg_tail = newmsg;
    }

    while (copysize < size) {
        struct msg_ext_item * ext = __get_msg_qobj(msgq);
        if (!ext)
            goto eagain;

        int sz = MSG_EXT_ITEM_DATA_SIZE(size - copysize);
        memcpy(ext->data, data + copysize, sz);
        ext->next = NULL;
        mtype->msg_tail->next = ext;
        mtype->msg_tail = (struct msg_item *) ext;
        copysize += sz;
    }

    msgq->nmsgs++;
    msgq->currentsize += size;
    return 0;

eagain:
    __free_msg_linked_qobjs(msgq, newmsg);

    if (mtype->msgs == newmsg)
        mtype->msgs = NULL;

    mtype->msg_tail = old_tail;
    return -EAGAIN;
}

static int msg_balance_migrate (struct shim_handle * hdl,
                                struct sysv_client * client);

static struct sysv_balance_policy msg_policy  = {
        .score_decay        = MSG_SCORE_DECAY,
        .score_max          = MSG_SCORE_MAX,
        .balance_threshold  = MSG_BALANCE_THRESHOLD,
        .migrate            = &msg_balance_migrate,
    };


DEFINE_PROFILE_INTERVAL(add_sysv_msg, sysv_msg);

int add_sysv_msg (struct shim_msg_handle * msgq,
                  long type, int size, const void * data,
                  struct sysv_client * src)
{
    BEGIN_PROFILE_INTERVAL();

    struct shim_handle * hdl = MSG_TO_HANDLE(msgq);
    int ret = 0;
    lock(hdl->lock);

    if (msgq->deleted) {
        ret = -EIDRM;
        goto out_locked;
    }

    if (!msgq->owned) {
        unlock(hdl->lock);
        ret = ipc_sysv_msgsnd_send(src->port, src->vmid, msgq->msqid,
                                   type, data, size, src->seq);
        goto out;
    }

    struct msg_type * mtype = __add_msg_type(type, &msgq->types,
                                             &msgq->ntypes,
                                             &msgq->maxtypes);

    if ((ret = __store_msg_qobjs(msgq, mtype, size, data)) < 0)
        goto out_locked;

    if (msgq->owned)
        __balance_sysv_score(&msg_policy, hdl, msgq->scores, MAX_SYSV_CLIENTS,
                             src, MSG_SND_SCORE);

    DkEventSet(msgq->event);
    ret  = 0;
out_locked:
    unlock(hdl->lock);
out:
    SAVE_PROFILE_INTERVAL(add_sysv_msg);
    return ret;
}

static struct msg_type *
__find_msg_type (int type, struct msg_type * types, int ntypes)
{
    for (struct msg_type * mtype = types ;
         mtype < &types[ntypes] && mtype->type <= type; mtype++)
        if (mtype->type == type)
            return mtype;
    return NULL;
}

static int __add_msg_req (struct shim_msg_handle * msgq,
                          struct msg_type * mtype,
                          int size, int flags, struct sysv_client * src)
{
    if (msgq->deleted)
        return -EIDRM;

    struct msg_req * req = __get_msg_qobj(msgq);
    if (!req)
        return -ENOMEM;

    get_ipc_port(src->port);

    req->next   = NULL;
    req->size   = size;
    req->flags  = flags;
    req->dest   = *src;

    if (mtype->req_tail) {
        mtype->req_tail->next = req;
        mtype->req_tail = req;
    } else {
        assert(!mtype->reqs);
        mtype->reqs = mtype->req_tail = req;
    }

    return 0;
}

DEFINE_PROFILE_INTERVAL(get_sysv_msg, sysv_msg);

int get_sysv_msg (struct shim_msg_handle * msgq,
                  long type, int size, void * data, int flags,
                  struct sysv_client * src)
{
    BEGIN_PROFILE_INTERVAL();
    int ret = 0;
    struct shim_handle * hdl = MSG_TO_HANDLE(msgq);
    struct msg_item * msg = NULL;
    struct msg_type * alltypes = NULL, * mtype = NULL;
    lock(hdl->lock);

    if (msgq->deleted) {
        ret = -EIDRM;
        goto out_locked;
    }

    if (msgq->owned) {
        __balance_sysv_score(&msg_policy, hdl, msgq->scores, MAX_SYSV_CLIENTS,
                             src, MSG_RCV_SCORE);

        if (!msgq->owned && src) {
            struct shim_ipc_info * owner = msgq->owner;
            assert(owner);
            ret = ipc_sysv_movres_send(src, owner->vmid,
                                       qstrgetstr(&owner->uri), msgq->lease,
                                       msgq->msqid, SYSV_MSGQ);
            goto out_locked;
        }
    }

    if (!msgq->owned) {
        IDTYPE msqid = msgq->msqid;

        if (src) {
            struct shim_ipc_info * owner = msgq->owner;
            ret = owner ?
                  ipc_sysv_movres_send(src, owner->vmid,
                                       qstrgetstr(&owner->uri), msgq->lease,
                                       msgq->msqid, SYSV_MSGQ) :
                  -ECONNREFUSED;
            goto out_locked;
        }

unowned:
        unlock(hdl->lock);
        ret = ipc_sysv_msgrcv_send(msqid, type, flags, data, size);
        if (ret != -EAGAIN &&
            ret != -ECONNREFUSED)
            goto out;

        lock(hdl->lock);

        if (!msgq->owned)
            goto out_locked;
    }

    while (1) {
        if (alltypes != msgq->types || !mtype || mtype->type != type) {
            alltypes = msgq->types;
            mtype = __find_msg_type(type, alltypes, msgq->ntypes);
        }

        if (mtype && mtype->msgs) {
            msg = mtype->msgs;
            if (msg->size > size && !(flags & MSG_NOERROR)) {
                ret = -E2BIG;
                goto out;
            }
            break;
        }

        if (flags & IPC_NOWAIT || src)
            break;

        unlock(hdl->lock);
        while (!DkObjectsWaitAny(1, &msgq->event, NO_TIMEOUT));
        lock(hdl->lock);

        if (!msgq->owned)
            goto unowned;
    }

    if (!msg) {
        ret = (!(flags & IPC_NOWAIT) && src) ?
            __add_msg_req(msgq, mtype, size, flags, src) : -ENOMSG;
        goto out_locked;
    }

    if ((ret = __load_msg_qobjs(msgq, mtype, msg, data)) < 0)
        goto out_locked;;

    ret = msg->size;
out_locked:
    unlock(hdl->lock);
out:
    SAVE_PROFILE_INTERVAL(get_sysv_msg);
    return ret;
}

static int __store_msg_persist (struct shim_msg_handle * msgq)
{
    int ret = 0;

   if (msgq->deleted)
        goto out;

    debug("store msgq %d to persistent store\n", msgq->msqid);

    char fileuri[20];
    snprintf(fileuri, 20, "file:msgq.%08x", msgq->msqid);

    PAL_HANDLE file = DkStreamOpen(fileuri, PAL_ACCESS_RDWR, 0600,
                                   PAL_CREAT_TRY, 0);
    if (!file) {
        ret = -PAL_ERRNO;
        goto out;
    }

    int expected_size = sizeof(struct msg_handle_backup) +
                        sizeof(struct msg_backup) * msgq->nmsgs +
                        msgq->currentsize;

    if (DkStreamSetLength(file, expected_size) != expected_size)
        goto err_file;

    void * mem = DkStreamMap(file, NULL, PAL_PROT_READ|PAL_PROT_WRITE,
                             0, ALIGN_UP(expected_size));
    if (!mem) {
        ret = -EFAULT;
        goto err_file;
    }

    struct msg_handle_backup * mback = mem;
    mem += sizeof(struct msg_handle_backup);

    mback->perm        = msgq->perm;
    mback->nmsgs       = msgq->nmsgs;
    mback->currentsize = msgq->currentsize;

    struct msg_type * mtype;
    for (mtype = msgq->types ; mtype < &msgq->types[msgq->ntypes] ;
         mtype++) {
        while (mtype->msgs) {
            struct msg_backup * msg = mem;
            mem += sizeof(struct msg_backup) + mtype->msgs->size;

            msg->type = mtype->type;
            msg->size = mtype->msgs->size;
            __load_msg_qobjs(msgq, mtype, mtype->msgs, msg->data);
        }

        mtype->msgs = mtype->msg_tail = NULL;
    }

    DkStreamUnmap(mem, ALIGN_UP(expected_size));

    if (msgq->owned)
        for (mtype = msgq->types ; mtype < &msgq->types[msgq->ntypes] ;
             mtype++) {
            struct msg_req * req = mtype->reqs;
            mtype->reqs = mtype->req_tail = NULL;
            while (req) {
                struct sysv_client * c = &req->dest;
                struct msg_req * next = req->next;

                __response_ipc_message(c->port, c->vmid, -EIDRM, c->seq);

                put_ipc_port(c->port);
                __free_msg_qobj(msgq, req);
                req = next;
            }
        }

    msgq->owned = false;
    ret = 0;
    goto out;

err_file:
    DkStreamDelete(file, 0);
    DkObjectClose(file);

out:
    // To wake up any receiver waiting on local message which must
    // now be requested from new owner.
    DkEventSet(msgq->event);
    return ret;
}

static int __load_msg_persist (struct shim_msg_handle * msgq, bool readmsg)
{
    int ret = 0;

    char fileuri[20];
    snprintf(fileuri, 20, "file:msgq.%08x", msgq->msqid);

    PAL_HANDLE file = DkStreamOpen(fileuri, PAL_ACCESS_RDONLY, 0, 0, 0);

    if (!file)
        return -EIDRM;

    struct msg_handle_backup mback;

    int bytes = DkStreamRead(file, 0, sizeof(struct msg_handle_backup),
                             &mback, NULL, 0);

    if (bytes < sizeof(struct msg_handle_backup)) {
        ret = bytes ? -EFAULT : -PAL_ERRNO;
        goto out;
    }

    msgq->perm = mback.perm;

    if (!readmsg || !mback.nmsgs)
        goto done;

    int expected_size = sizeof(struct msg_handle_backup) +
                        sizeof(struct msg_backup) * mback.nmsgs +
                        mback.currentsize;

    void * mem = DkStreamMap(file, NULL, PAL_PROT_READ,
                             0, ALIGN_UP(expected_size));

    if (!mem) {
        ret = -PAL_ERRNO;
        goto out;
    }

    mem += sizeof(struct msg_handle_backup);

    struct msg_type * mtype = NULL;
    for (int i = 0 ; i < mback.nmsgs ; i++) {
        struct msg_backup * m = mem;
        mem += sizeof(struct msg_backup) + m->size;

        debug("load msg: type=%d, size=%d\n", m->type, m->size);

        if (!mtype || mtype->type != m->type)
            mtype = __add_msg_type(m->type, &msgq->types, &msgq->ntypes,
                                   &msgq->maxtypes);

        if ((ret = __store_msg_qobjs(msgq, mtype, m->size, m->data)) < 0)
            goto out;
    };

    DkStreamUnmap(mem, ALIGN_UP(expected_size));

done:
    DkStreamDelete(file, 0);
    ret = 0;
    goto out;

out:
    DkObjectClose(file);
    return ret;
}

int store_all_msg_persist (void)
{
    struct shim_msg_handle * msgq, *n;

    lock(msgq_list_lock);

    list_for_each_entry_safe(msgq, n, &msgq_list, list)
        if (msgq->owned) {
            struct shim_handle * hdl = container_of(msgq, struct shim_handle,
                                                    info.msg);
            lock(hdl->lock);
            __store_msg_persist(msgq);
            unlock(hdl->lock);
        }

    unlock(msgq_list_lock);
    return 0;
}

int shim_do_msgpersist (int msqid, int cmd)
{
    struct shim_msg_handle * msgq;
    struct shim_handle * hdl;
    int ret = -EINVAL;

    switch (cmd) {
        case MSGPERSIST_STORE:
            msgq = get_msg_handle_by_id(msqid);
            if (!msgq)
                return -EINVAL;

            hdl = container_of(msgq, struct shim_handle, info.msg);
            lock(hdl->lock);
            ret = __store_msg_persist(msgq);
            unlock(hdl->lock);
            put_msg_handle(msgq);
            break;

        case MSGPERSIST_LOAD:
            lock(msgq_list_lock);
            ret = __add_msg_handle(0, msqid, false, &msgq);
            if (!ret)
                ret = __load_msg_persist(msgq, true);
            unlock(msgq_list_lock);
            put_msg_handle(msgq);
            break;
    }

    return ret;
}

static int msg_balance_migrate (struct shim_handle * hdl,
                                struct sysv_client * src)
{
    struct shim_msg_handle * msgq = &hdl->info.msg;
    int ret = 0;

    debug("trigger msg queue balancing, migrate to process %u\n", src->vmid);

    if ((ret = __store_msg_persist(msgq)) < 0)
        return 0;

    struct shim_ipc_info * info = discover_client(src->port, src->vmid);
    if (!info)
        goto failed;

    ipc_sysv_sublease_send(src->vmid, msgq->msqid,
                           qstrgetstr(&info->uri),
                           &msgq->lease);

    ret = ipc_sysv_msgmov_send(src->port, src->vmid, msgq->msqid, msgq->lease,
                               msgq->scores, MAX_SYSV_CLIENTS);
    if (ret < 0)
        goto failed_info;

    msgq->owner = info;

    for (struct msg_type * mtype = msgq->types ;
         mtype < &msgq->types[msgq->ntypes] ; mtype++) {
        struct msg_req * req = mtype->reqs;
        mtype->reqs = mtype->req_tail = NULL;
        while (req) {
            struct msg_req * next = req->next;

            ipc_sysv_movres_send(&req->dest, info->vmid, qstrgetstr(&info->uri),
                                 msgq->lease, msgq->msqid, SYSV_MSGQ);

            put_ipc_port(req->dest.port);
            __free_msg_qobj(msgq, req);
            req = next;
        }
    }

    ret = 0;
    DkEventSet(msgq->event);
    goto out;

failed_info:
    put_ipc_info(info);
failed:
    ret = __load_msg_persist(msgq, true);
out:
    return ret;
}