[mirror_qemu.git] / blockjob.c

/*
 * QEMU System Emulator block driver
 *
 * Copyright (c) 2011 IBM Corp.
 * Copyright (c) 2012 Red Hat, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "config-host.h"
#include "qemu-common.h"
#include "trace.h"
#include "block/block.h"
#include "block/blockjob.h"
#include "block/block_int.h"
#include "qapi/qmp/qerror.h"
#include "qapi/qmp/qjson.h"
#include "block/coroutine.h"
#include "qmp-commands.h"
#include "qemu/timer.h"
#include "qapi-event.h"

void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
                       int64_t speed, BlockCompletionFunc *cb,
                       void *opaque, Error **errp)
{
    BlockJob *job;

    if (bs->job) {
        error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
        return NULL;
    }
    bdrv_ref(bs);
    job = g_malloc0(driver->instance_size);
    error_setg(&job->blocker, "block device is in use by block job: %s",
               BlockJobType_lookup[driver->job_type]);
    bdrv_op_block_all(bs, job->blocker);
    bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);

    job->driver        = driver;
    job->bs            = bs;
    job->cb            = cb;
    job->opaque        = opaque;
    job->busy          = true;
    bs->job = job;

    /* Only set speed when necessary to avoid NotSupported error */
    if (speed != 0) {
        Error *local_err = NULL;

        block_job_set_speed(job, speed, &local_err);
        if (local_err) {
            bs->job = NULL;
            bdrv_op_unblock_all(bs, job->blocker);
            error_free(job->blocker);
            g_free(job);
            error_propagate(errp, local_err);
            return NULL;
        }
    }
    return job;
}

void block_job_completed(BlockJob *job, int ret)
{
    BlockDriverState *bs = job->bs;

    assert(bs->job == job);
    job->cb(job->opaque, ret);
    bs->job = NULL;
    bdrv_op_unblock_all(bs, job->blocker);
    error_free(job->blocker);
    g_free(job);
}

void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
{
    Error *local_err = NULL;

    if (!job->driver->set_speed) {
        error_setg(errp, QERR_UNSUPPORTED);
        return;
    }
    job->driver->set_speed(job, speed, &local_err);
    if (local_err) {
        error_propagate(errp, local_err);
        return;
    }

    job->speed = speed;
}

void block_job_complete(BlockJob *job, Error **errp)
{
    if (job->pause_count || job->cancelled || !job->driver->complete) {
        error_setg(errp, QERR_BLOCK_JOB_NOT_READY,
                   bdrv_get_device_name(job->bs));
        return;
    }

    job->driver->complete(job, errp);
}

void block_job_pause(BlockJob *job)
{
    job->pause_count++;
}

bool block_job_is_paused(BlockJob *job)
{
    return job->pause_count > 0;
}

void block_job_resume(BlockJob *job)
{
    assert(job->pause_count > 0);
    job->pause_count--;
    if (job->pause_count) {
        return;
    }
    block_job_enter(job);
}

void block_job_enter(BlockJob *job)
{
    block_job_iostatus_reset(job);
    if (job->co && !job->busy) {
        qemu_coroutine_enter(job->co, NULL);
    }
}

void block_job_cancel(BlockJob *job)
{
    job->cancelled = true;
    block_job_enter(job);
}

bool block_job_is_cancelled(BlockJob *job)
{
    return job->cancelled;
}

void block_job_iostatus_reset(BlockJob *job)
{
    job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
    if (job->driver->iostatus_reset) {
        job->driver->iostatus_reset(job);
    }
}

struct BlockFinishData {
    BlockJob *job;
    BlockCompletionFunc *cb;
    void *opaque;
    bool cancelled;
    int ret;
};

static void block_job_finish_cb(void *opaque, int ret)
{
    struct BlockFinishData *data = opaque;

    data->cancelled = block_job_is_cancelled(data->job);
    data->ret = ret;
    data->cb(data->opaque, ret);
}

static int block_job_finish_sync(BlockJob *job,
                                 void (*finish)(BlockJob *, Error **errp),
                                 Error **errp)
{
    struct BlockFinishData data;
    BlockDriverState *bs = job->bs;
    Error *local_err = NULL;

    assert(bs->job == job);

    /* Set up our own callback to store the result and chain to
     * the original callback.
     */
    data.job = job;
    data.cb = job->cb;
    data.opaque = job->opaque;
    data.ret = -EINPROGRESS;
    job->cb = block_job_finish_cb;
    job->opaque = &data;
    finish(job, &local_err);
    if (local_err) {
        error_propagate(errp, local_err);
        return -EBUSY;
    }
    while (data.ret == -EINPROGRESS) {
        aio_poll(bdrv_get_aio_context(bs), true);
    }
    return (data.cancelled && data.ret == 0) ? -ECANCELED : data.ret;
}

/* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
 * used with block_job_finish_sync() without the need for (rather nasty)
 * function pointer casts there. */
static void block_job_cancel_err(BlockJob *job, Error **errp)
{
    block_job_cancel(job);
}

int block_job_cancel_sync(BlockJob *job)
{
    return block_job_finish_sync(job, &block_job_cancel_err, NULL);
}

int block_job_complete_sync(BlockJob *job, Error **errp)
{
    return block_job_finish_sync(job, &block_job_complete, errp);
}

void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
{
    assert(job->busy);

    /* Check cancellation *before* setting busy = false, too!  */
    if (block_job_is_cancelled(job)) {
        return;
    }

    job->busy = false;
    if (block_job_is_paused(job)) {
        qemu_coroutine_yield();
    } else {
        co_aio_sleep_ns(bdrv_get_aio_context(job->bs), type, ns);
    }
    job->busy = true;
}

void block_job_yield(BlockJob *job)
{
    assert(job->busy);

    /* Check cancellation *before* setting busy = false, too!  */
    if (block_job_is_cancelled(job)) {
        return;
    }

    job->busy = false;
    qemu_coroutine_yield();
    job->busy = true;
}

BlockJobInfo *block_job_query(BlockJob *job)
{
    BlockJobInfo *info = g_new0(BlockJobInfo, 1);
    info->type      = g_strdup(BlockJobType_lookup[job->driver->job_type]);
    info->device    = g_strdup(bdrv_get_device_name(job->bs));
    info->len       = job->len;
    info->busy      = job->busy;
    info->paused    = job->pause_count > 0;
    info->offset    = job->offset;
    info->speed     = job->speed;
    info->io_status = job->iostatus;
    info->ready     = job->ready;
    return info;
}

static void block_job_iostatus_set_err(BlockJob *job, int error)
{
    if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
        job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
                                          BLOCK_DEVICE_IO_STATUS_FAILED;
    }
}

void block_job_event_cancelled(BlockJob *job)
{
    qapi_event_send_block_job_cancelled(job->driver->job_type,
                                        bdrv_get_device_name(job->bs),
                                        job->len,
                                        job->offset,
                                        job->speed,
                                        &error_abort);
}

void block_job_event_completed(BlockJob *job, const char *msg)
{
    qapi_event_send_block_job_completed(job->driver->job_type,
                                        bdrv_get_device_name(job->bs),
                                        job->len,
                                        job->offset,
                                        job->speed,
                                        !!msg,
                                        msg,
                                        &error_abort);
}

void block_job_event_ready(BlockJob *job)
{
    job->ready = true;

    qapi_event_send_block_job_ready(job->driver->job_type,
                                    bdrv_get_device_name(job->bs),
                                    job->len,
                                    job->offset,
                                    job->speed, &error_abort);
}

BlockErrorAction block_job_error_action(BlockJob *job, BlockDriverState *bs,
                                        BlockdevOnError on_err,
                                        int is_read, int error)
{
    BlockErrorAction action;

    switch (on_err) {
    case BLOCKDEV_ON_ERROR_ENOSPC:
        action = (error == ENOSPC) ?
                 BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
        break;
    case BLOCKDEV_ON_ERROR_STOP:
        action = BLOCK_ERROR_ACTION_STOP;
        break;
    case BLOCKDEV_ON_ERROR_REPORT:
        action = BLOCK_ERROR_ACTION_REPORT;
        break;
    case BLOCKDEV_ON_ERROR_IGNORE:
        action = BLOCK_ERROR_ACTION_IGNORE;
        break;
    default:
        abort();
    }
    qapi_event_send_block_job_error(bdrv_get_device_name(job->bs),
                                    is_read ? IO_OPERATION_TYPE_READ :
                                    IO_OPERATION_TYPE_WRITE,
                                    action, &error_abort);
    if (action == BLOCK_ERROR_ACTION_STOP) {
        /* make the pause user visible, which will be resumed from QMP. */
        job->user_paused = true;
        block_job_pause(job);
        block_job_iostatus_set_err(job, error);
        if (bs != job->bs) {
            bdrv_iostatus_set_err(bs, error);
        }
    }
    return action;
}

typedef struct {
    BlockJob *job;
    QEMUBH *bh;
    AioContext *aio_context;
    BlockJobDeferToMainLoopFn *fn;
    void *opaque;
} BlockJobDeferToMainLoopData;

static void block_job_defer_to_main_loop_bh(void *opaque)
{
    BlockJobDeferToMainLoopData *data = opaque;
    AioContext *aio_context;

    qemu_bh_delete(data->bh);

    /* Prevent race with block_job_defer_to_main_loop() */
    aio_context_acquire(data->aio_context);

    /* Fetch BDS AioContext again, in case it has changed */
    aio_context = bdrv_get_aio_context(data->job->bs);
    aio_context_acquire(aio_context);

    data->fn(data->job, data->opaque);

    aio_context_release(aio_context);

    aio_context_release(data->aio_context);

    g_free(data);
}

void block_job_defer_to_main_loop(BlockJob *job,
                                  BlockJobDeferToMainLoopFn *fn,
                                  void *opaque)
{
    BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
    data->job = job;
    data->bh = qemu_bh_new(block_job_defer_to_main_loop_bh, data);
    data->aio_context = bdrv_get_aio_context(job->bs);
    data->fn = fn;
    data->opaque = opaque;

    qemu_bh_schedule(data->bh);
}
Commit	Line	Data
	1	/*
	2	* QEMU System Emulator block driver
	3	*
	4	* Copyright (c) 2011 IBM Corp.
	5	* Copyright (c) 2012 Red Hat, Inc.
	6	*
	7	* Permission is hereby granted, free of charge, to any person obtaining a copy
	8	* of this software and associated documentation files (the "Software"), to deal
	9	* in the Software without restriction, including without limitation the rights
	10	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	11	* copies of the Software, and to permit persons to whom the Software is
	12	* furnished to do so, subject to the following conditions:
	13	*
	14	* The above copyright notice and this permission notice shall be included in
	15	* all copies or substantial portions of the Software.
	16	*
	17	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	18	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	19	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	20	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	21	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	22	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	23	* THE SOFTWARE.
	24	*/
	25
	26	#include "config-host.h"
	27	#include "qemu-common.h"
	28	#include "trace.h"
	29	#include "block/block.h"
	30	#include "block/blockjob.h"
	31	#include "block/block_int.h"
	32	#include "qapi/qmp/qerror.h"
	33	#include "qapi/qmp/qjson.h"
	34	#include "block/coroutine.h"
	35	#include "qmp-commands.h"
	36	#include "qemu/timer.h"
	37	#include "qapi-event.h"
	38
	39	void block_job_create(const BlockJobDriver driver, BlockDriverState *bs,
	40	int64_t speed, BlockCompletionFunc *cb,
	41	void opaque, Error *errp)
	42	{
	43	BlockJob *job;
	44
	45	if (bs->job) {
	46	error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
	47	return NULL;
	48	}
	49	bdrv_ref(bs);
	50	job = g_malloc0(driver->instance_size);
	51	error_setg(&job->blocker, "block device is in use by block job: %s",
	52	BlockJobType_lookup[driver->job_type]);
	53	bdrv_op_block_all(bs, job->blocker);
	54	bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);
	55
	56	job->driver = driver;
	57	job->bs = bs;
	58	job->cb = cb;
	59	job->opaque = opaque;
	60	job->busy = true;
	61	bs->job = job;
	62
	63	/* Only set speed when necessary to avoid NotSupported error */
	64	if (speed != 0) {
	65	Error *local_err = NULL;
	66
	67	block_job_set_speed(job, speed, &local_err);
	68	if (local_err) {
	69	bs->job = NULL;
	70	bdrv_op_unblock_all(bs, job->blocker);
	71	error_free(job->blocker);
	72	g_free(job);
	73	error_propagate(errp, local_err);
	74	return NULL;
	75	}
	76	}
	77	return job;
	78	}
	79
	80	void block_job_completed(BlockJob *job, int ret)
	81	{
	82	BlockDriverState *bs = job->bs;
	83
	84	assert(bs->job == job);
	85	job->cb(job->opaque, ret);
	86	bs->job = NULL;
	87	bdrv_op_unblock_all(bs, job->blocker);
	88	error_free(job->blocker);
	89	g_free(job);
	90	}
	91
	92	void block_job_set_speed(BlockJob job, int64_t speed, Error *errp)
	93	{
	94	Error *local_err = NULL;
	95
	96	if (!job->driver->set_speed) {
	97	error_setg(errp, QERR_UNSUPPORTED);
	98	return;
	99	}
	100	job->driver->set_speed(job, speed, &local_err);
	101	if (local_err) {
	102	error_propagate(errp, local_err);
	103	return;
	104	}
	105
	106	job->speed = speed;
	107	}
	108
	109	void block_job_complete(BlockJob job, Error *errp)
	110	{
	111	if (job->pause_count \|\| job->cancelled \|\| !job->driver->complete) {
	112	error_setg(errp, QERR_BLOCK_JOB_NOT_READY,
	113	bdrv_get_device_name(job->bs));
	114	return;
	115	}
	116
	117	job->driver->complete(job, errp);
	118	}
	119
	120	void block_job_pause(BlockJob *job)
	121	{
	122	job->pause_count++;
	123	}
	124
	125	bool block_job_is_paused(BlockJob *job)
	126	{
	127	return job->pause_count > 0;
	128	}
	129
	130	void block_job_resume(BlockJob *job)
	131	{
	132	assert(job->pause_count > 0);
	133	job->pause_count--;
	134	if (job->pause_count) {
	135	return;
	136	}
	137	block_job_enter(job);
	138	}
	139
	140	void block_job_enter(BlockJob *job)
	141	{
	142	block_job_iostatus_reset(job);
	143	if (job->co && !job->busy) {
	144	qemu_coroutine_enter(job->co, NULL);
	145	}
	146	}
	147
	148	void block_job_cancel(BlockJob *job)
	149	{
	150	job->cancelled = true;
	151	block_job_enter(job);
	152	}
	153
	154	bool block_job_is_cancelled(BlockJob *job)
	155	{
	156	return job->cancelled;
	157	}
	158
	159	void block_job_iostatus_reset(BlockJob *job)
	160	{
	161	job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
	162	if (job->driver->iostatus_reset) {
	163	job->driver->iostatus_reset(job);
	164	}
	165	}
	166
	167	struct BlockFinishData {
	168	BlockJob *job;
	169	BlockCompletionFunc *cb;
	170	void *opaque;
	171	bool cancelled;
	172	int ret;
	173	};
	174
	175	static void block_job_finish_cb(void *opaque, int ret)
	176	{
	177	struct BlockFinishData *data = opaque;
	178
	179	data->cancelled = block_job_is_cancelled(data->job);
	180	data->ret = ret;
	181	data->cb(data->opaque, ret);
	182	}
	183
	184	static int block_job_finish_sync(BlockJob *job,
	185	void (finish)(BlockJob , Error **errp),
	186	Error **errp)
	187	{
	188	struct BlockFinishData data;
	189	BlockDriverState *bs = job->bs;
	190	Error *local_err = NULL;
	191
	192	assert(bs->job == job);
	193
	194	/* Set up our own callback to store the result and chain to
	195	* the original callback.
	196	*/
	197	data.job = job;
	198	data.cb = job->cb;
	199	data.opaque = job->opaque;
	200	data.ret = -EINPROGRESS;
	201	job->cb = block_job_finish_cb;
	202	job->opaque = &data;
	203	finish(job, &local_err);
	204	if (local_err) {
	205	error_propagate(errp, local_err);
	206	return -EBUSY;
	207	}
	208	while (data.ret == -EINPROGRESS) {
	209	aio_poll(bdrv_get_aio_context(bs), true);
	210	}
	211	return (data.cancelled && data.ret == 0) ? -ECANCELED : data.ret;
	212	}
	213
	214	/* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
	215	* used with block_job_finish_sync() without the need for (rather nasty)
	216	* function pointer casts there. */
	217	static void block_job_cancel_err(BlockJob job, Error *errp)
	218	{
	219	block_job_cancel(job);
	220	}
	221
	222	int block_job_cancel_sync(BlockJob *job)
	223	{
	224	return block_job_finish_sync(job, &block_job_cancel_err, NULL);
	225	}
	226
	227	int block_job_complete_sync(BlockJob job, Error *errp)
	228	{
	229	return block_job_finish_sync(job, &block_job_complete, errp);
	230	}
	231
	232	void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
	233	{
	234	assert(job->busy);
	235
	236	/* Check cancellation before setting busy = false, too! */
	237	if (block_job_is_cancelled(job)) {
	238	return;
	239	}
	240
	241	job->busy = false;
	242	if (block_job_is_paused(job)) {
	243	qemu_coroutine_yield();
	244	} else {
	245	co_aio_sleep_ns(bdrv_get_aio_context(job->bs), type, ns);
	246	}
	247	job->busy = true;
	248	}
	249
	250	void block_job_yield(BlockJob *job)
	251	{
	252	assert(job->busy);
	253
	254	/* Check cancellation before setting busy = false, too! */
	255	if (block_job_is_cancelled(job)) {
	256	return;
	257	}
	258
	259	job->busy = false;
	260	qemu_coroutine_yield();
	261	job->busy = true;
	262	}
	263
	264	BlockJobInfo block_job_query(BlockJob job)
	265	{
	266	BlockJobInfo *info = g_new0(BlockJobInfo, 1);
	267	info->type = g_strdup(BlockJobType_lookup[job->driver->job_type]);
	268	info->device = g_strdup(bdrv_get_device_name(job->bs));
	269	info->len = job->len;
	270	info->busy = job->busy;
	271	info->paused = job->pause_count > 0;
	272	info->offset = job->offset;
	273	info->speed = job->speed;
	274	info->io_status = job->iostatus;
	275	info->ready = job->ready;
	276	return info;
	277	}
	278
	279	static void block_job_iostatus_set_err(BlockJob *job, int error)
	280	{
	281	if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
	282	job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
	283	BLOCK_DEVICE_IO_STATUS_FAILED;
	284	}
	285	}
	286
	287	void block_job_event_cancelled(BlockJob *job)
	288	{
	289	qapi_event_send_block_job_cancelled(job->driver->job_type,
	290	bdrv_get_device_name(job->bs),
	291	job->len,
	292	job->offset,
	293	job->speed,
	294	&error_abort);
	295	}
	296
	297	void block_job_event_completed(BlockJob job, const char msg)
	298	{
	299	qapi_event_send_block_job_completed(job->driver->job_type,
	300	bdrv_get_device_name(job->bs),
	301	job->len,
	302	job->offset,
	303	job->speed,
	304	!!msg,
	305	msg,
	306	&error_abort);
	307	}
	308
	309	void block_job_event_ready(BlockJob *job)
	310	{
	311	job->ready = true;
	312
	313	qapi_event_send_block_job_ready(job->driver->job_type,
	314	bdrv_get_device_name(job->bs),
	315	job->len,
	316	job->offset,
	317	job->speed, &error_abort);
	318	}
	319
	320	BlockErrorAction block_job_error_action(BlockJob job, BlockDriverState bs,
	321	BlockdevOnError on_err,
	322	int is_read, int error)
	323	{
	324	BlockErrorAction action;
	325
	326	switch (on_err) {
	327	case BLOCKDEV_ON_ERROR_ENOSPC:
	328	action = (error == ENOSPC) ?
	329	BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
	330	break;
	331	case BLOCKDEV_ON_ERROR_STOP:
	332	action = BLOCK_ERROR_ACTION_STOP;
	333	break;
	334	case BLOCKDEV_ON_ERROR_REPORT:
	335	action = BLOCK_ERROR_ACTION_REPORT;
	336	break;
	337	case BLOCKDEV_ON_ERROR_IGNORE:
	338	action = BLOCK_ERROR_ACTION_IGNORE;
	339	break;
	340	default:
	341	abort();
	342	}
	343	qapi_event_send_block_job_error(bdrv_get_device_name(job->bs),
	344	is_read ? IO_OPERATION_TYPE_READ :
	345	IO_OPERATION_TYPE_WRITE,
	346	action, &error_abort);
	347	if (action == BLOCK_ERROR_ACTION_STOP) {
	348	/* make the pause user visible, which will be resumed from QMP. */
	349	job->user_paused = true;
	350	block_job_pause(job);
	351	block_job_iostatus_set_err(job, error);
	352	if (bs != job->bs) {
	353	bdrv_iostatus_set_err(bs, error);
	354	}
	355	}
	356	return action;
	357	}
	358
	359	typedef struct {
	360	BlockJob *job;
	361	QEMUBH *bh;
	362	AioContext *aio_context;
	363	BlockJobDeferToMainLoopFn *fn;
	364	void *opaque;
	365	} BlockJobDeferToMainLoopData;
	366
	367	static void block_job_defer_to_main_loop_bh(void *opaque)
	368	{
	369	BlockJobDeferToMainLoopData *data = opaque;
	370	AioContext *aio_context;
	371
	372	qemu_bh_delete(data->bh);
	373
	374	/* Prevent race with block_job_defer_to_main_loop() */
	375	aio_context_acquire(data->aio_context);
	376
	377	/* Fetch BDS AioContext again, in case it has changed */
	378	aio_context = bdrv_get_aio_context(data->job->bs);
	379	aio_context_acquire(aio_context);
	380
	381	data->fn(data->job, data->opaque);
	382
	383	aio_context_release(aio_context);
	384
	385	aio_context_release(data->aio_context);
	386
	387	g_free(data);
	388	}
	389
	390	void block_job_defer_to_main_loop(BlockJob *job,
	391	BlockJobDeferToMainLoopFn *fn,
	392	void *opaque)
	393	{
	394	BlockJobDeferToMainLoopData data = g_malloc(sizeof(data));
	395	data->job = job;
	396	data->bh = qemu_bh_new(block_job_defer_to_main_loop_bh, data);
	397	data->aio_context = bdrv_get_aio_context(job->bs);
	398	data->fn = fn;
	399	data->opaque = opaque;
	400
	401	qemu_bh_schedule(data->bh);
	402	}