Add qemu 2.4.0

Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>

1 files changed, 823 insertions, 0 deletions

diff --git a/qemu/block/mirror.c b/qemu/block/mirror.c
new file mode 100644
index 000000000..fc4d8f561
--- /dev/null
+++ b/qemu/block/mirror.c
@@ -0,0 +1,823 @@
+/*
+ * Image mirroring
+ *
+ * Copyright Red Hat, Inc. 2012
+ *
+ * Authors:
+ *  Paolo Bonzini  <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include "trace.h"
+#include "block/blockjob.h"
+#include "block/block_int.h"
+#include "qapi/qmp/qerror.h"
+#include "qemu/ratelimit.h"
+#include "qemu/bitmap.h"
+
+#define SLICE_TIME    100000000ULL /* ns */
+#define MAX_IN_FLIGHT 16
+#define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
+
+/* The mirroring buffer is a list of granularity-sized chunks.
+ * Free chunks are organized in a list.
+ */
+typedef struct MirrorBuffer {
+    QSIMPLEQ_ENTRY(MirrorBuffer) next;
+} MirrorBuffer;
+
+typedef struct MirrorBlockJob {
+    BlockJob common;
+    RateLimit limit;
+    BlockDriverState *target;
+    BlockDriverState *base;
+    /* The name of the graph node to replace */
+    char *replaces;
+    /* The BDS to replace */
+    BlockDriverState *to_replace;
+    /* Used to block operations on the drive-mirror-replace target */
+    Error *replace_blocker;
+    bool is_none_mode;
+    BlockdevOnError on_source_error, on_target_error;
+    bool synced;
+    bool should_complete;
+    int64_t sector_num;
+    int64_t granularity;
+    size_t buf_size;
+    int64_t bdev_length;
+    unsigned long *cow_bitmap;
+    BdrvDirtyBitmap *dirty_bitmap;
+    HBitmapIter hbi;
+    uint8_t *buf;
+    QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
+    int buf_free_count;
+
+    unsigned long *in_flight_bitmap;
+    int in_flight;
+    int sectors_in_flight;
+    int ret;
+    bool unmap;
+} MirrorBlockJob;
+
+typedef struct MirrorOp {
+    MirrorBlockJob *s;
+    QEMUIOVector qiov;
+    int64_t sector_num;
+    int nb_sectors;
+} MirrorOp;
+
+static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
+                                            int error)
+{
+    s->synced = false;
+    if (read) {
+        return block_job_error_action(&s->common, s->common.bs,
+                                      s->on_source_error, true, error);
+    } else {
+        return block_job_error_action(&s->common, s->target,
+                                      s->on_target_error, false, error);
+    }
+}
+
+static void mirror_iteration_done(MirrorOp *op, int ret)
+{
+    MirrorBlockJob *s = op->s;
+    struct iovec *iov;
+    int64_t chunk_num;
+    int i, nb_chunks, sectors_per_chunk;
+
+    trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);
+
+    s->in_flight--;
+    s->sectors_in_flight -= op->nb_sectors;
+    iov = op->qiov.iov;
+    for (i = 0; i < op->qiov.niov; i++) {
+        MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
+        QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
+        s->buf_free_count++;
+    }
+
+    sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
+    chunk_num = op->sector_num / sectors_per_chunk;
+    nb_chunks = op->nb_sectors / sectors_per_chunk;
+    bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
+    if (ret >= 0) {
+        if (s->cow_bitmap) {
+            bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
+        }
+        s->common.offset += (uint64_t)op->nb_sectors * BDRV_SECTOR_SIZE;
+    }
+
+    qemu_iovec_destroy(&op->qiov);
+    g_slice_free(MirrorOp, op);
+
+    /* Enter coroutine when it is not sleeping.  The coroutine sleeps to
+     * rate-limit itself.  The coroutine will eventually resume since there is
+     * a sleep timeout so don't wake it early.
+     */
+    if (s->common.busy) {
+        qemu_coroutine_enter(s->common.co, NULL);
+    }
+}
+
+static void mirror_write_complete(void *opaque, int ret)
+{
+    MirrorOp *op = opaque;
+    MirrorBlockJob *s = op->s;
+    if (ret < 0) {
+        BlockErrorAction action;
+
+        bdrv_set_dirty_bitmap(s->dirty_bitmap, op->sector_num, op->nb_sectors);
+        action = mirror_error_action(s, false, -ret);
+        if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
+            s->ret = ret;
+        }
+    }
+    mirror_iteration_done(op, ret);
+}
+
+static void mirror_read_complete(void *opaque, int ret)
+{
+    MirrorOp *op = opaque;
+    MirrorBlockJob *s = op->s;
+    if (ret < 0) {
+        BlockErrorAction action;
+
+        bdrv_set_dirty_bitmap(s->dirty_bitmap, op->sector_num, op->nb_sectors);
+        action = mirror_error_action(s, true, -ret);
+        if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
+            s->ret = ret;
+        }
+
+        mirror_iteration_done(op, ret);
+        return;
+    }
+    bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors,
+                    mirror_write_complete, op);
+}
+
+static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
+{
+    BlockDriverState *source = s->common.bs;
+    int nb_sectors, sectors_per_chunk, nb_chunks;
+    int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
+    uint64_t delay_ns = 0;
+    MirrorOp *op;
+    int pnum;
+    int64_t ret;
+
+    s->sector_num = hbitmap_iter_next(&s->hbi);
+    if (s->sector_num < 0) {
+        bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
+        s->sector_num = hbitmap_iter_next(&s->hbi);
+        trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap));
+        assert(s->sector_num >= 0);
+    }
+
+    hbitmap_next_sector = s->sector_num;
+    sector_num = s->sector_num;
+    sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
+    end = s->bdev_length / BDRV_SECTOR_SIZE;
+
+    /* Extend the QEMUIOVector to include all adjacent blocks that will
+     * be copied in this operation.
+     *
+     * We have to do this if we have no backing file yet in the destination,
+     * and the cluster size is very large.  Then we need to do COW ourselves.
+     * The first time a cluster is copied, copy it entirely.  Note that,
+     * because both the granularity and the cluster size are powers of two,
+     * the number of sectors to copy cannot exceed one cluster.
+     *
+     * We also want to extend the QEMUIOVector to include more adjacent
+     * dirty blocks if possible, to limit the number of I/O operations and
+     * run efficiently even with a small granularity.
+     */
+    nb_chunks = 0;
+    nb_sectors = 0;
+    next_sector = sector_num;
+    next_chunk = sector_num / sectors_per_chunk;
+
+    /* Wait for I/O to this cluster (from a previous iteration) to be done.  */
+    while (test_bit(next_chunk, s->in_flight_bitmap)) {
+        trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
+        qemu_coroutine_yield();
+    }
+
+    do {
+        int added_sectors, added_chunks;
+
+        if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) ||
+            test_bit(next_chunk, s->in_flight_bitmap)) {
+            assert(nb_sectors > 0);
+            break;
+        }
+
+        added_sectors = sectors_per_chunk;
+        if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) {
+            bdrv_round_to_clusters(s->target,
+                                   next_sector, added_sectors,
+                                   &next_sector, &added_sectors);
+
+            /* On the first iteration, the rounding may make us copy
+             * sectors before the first dirty one.
+             */
+            if (next_sector < sector_num) {
+                assert(nb_sectors == 0);
+                sector_num = next_sector;
+                next_chunk = next_sector / sectors_per_chunk;
+            }
+        }
+
+        added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors));
+        added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk;
+
+        /* When doing COW, it may happen that there is not enough space for
+         * a full cluster.  Wait if that is the case.
+         */
+        while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
+            trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
+            qemu_coroutine_yield();
+        }
+        if (s->buf_free_count < nb_chunks + added_chunks) {
+            trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
+            break;
+        }
+
+        /* We have enough free space to copy these sectors.  */
+        bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
+
+        nb_sectors += added_sectors;
+        nb_chunks += added_chunks;
+        next_sector += added_sectors;
+        next_chunk += added_chunks;
+        if (!s->synced && s->common.speed) {
+            delay_ns = ratelimit_calculate_delay(&s->limit, added_sectors);
+        }
+    } while (delay_ns == 0 && next_sector < end);
+
+    /* Allocate a MirrorOp that is used as an AIO callback.  */
+    op = g_slice_new(MirrorOp);
+    op->s = s;
+    op->sector_num = sector_num;
+    op->nb_sectors = nb_sectors;
+
+    /* Now make a QEMUIOVector taking enough granularity-sized chunks
+     * from s->buf_free.
+     */
+    qemu_iovec_init(&op->qiov, nb_chunks);
+    next_sector = sector_num;
+    while (nb_chunks-- > 0) {
+        MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
+        size_t remaining = (nb_sectors * BDRV_SECTOR_SIZE) - op->qiov.size;
+
+        QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
+        s->buf_free_count--;
+        qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining));
+
+        /* Advance the HBitmapIter in parallel, so that we do not examine
+         * the same sector twice.
+         */
+        if (next_sector > hbitmap_next_sector
+            && bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) {
+            hbitmap_next_sector = hbitmap_iter_next(&s->hbi);
+        }
+
+        next_sector += sectors_per_chunk;
+    }
+
+    bdrv_reset_dirty_bitmap(s->dirty_bitmap, sector_num, nb_sectors);
+
+    /* Copy the dirty cluster.  */
+    s->in_flight++;
+    s->sectors_in_flight += nb_sectors;
+    trace_mirror_one_iteration(s, sector_num, nb_sectors);
+
+    ret = bdrv_get_block_status_above(source, NULL, sector_num,
+                                      nb_sectors, &pnum);
+    if (ret < 0 || pnum < nb_sectors ||
+            (ret & BDRV_BLOCK_DATA && !(ret & BDRV_BLOCK_ZERO))) {
+        bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
+                       mirror_read_complete, op);
+    } else if (ret & BDRV_BLOCK_ZERO) {
+        bdrv_aio_write_zeroes(s->target, sector_num, op->nb_sectors,
+                              s->unmap ? BDRV_REQ_MAY_UNMAP : 0,
+                              mirror_write_complete, op);
+    } else {
+        assert(!(ret & BDRV_BLOCK_DATA));
+        bdrv_aio_discard(s->target, sector_num, op->nb_sectors,
+                         mirror_write_complete, op);
+    }
+    return delay_ns;
+}
+
+static void mirror_free_init(MirrorBlockJob *s)
+{
+    int granularity = s->granularity;
+    size_t buf_size = s->buf_size;
+    uint8_t *buf = s->buf;
+
+    assert(s->buf_free_count == 0);
+    QSIMPLEQ_INIT(&s->buf_free);
+    while (buf_size != 0) {
+        MirrorBuffer *cur = (MirrorBuffer *)buf;
+        QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);
+        s->buf_free_count++;
+        buf_size -= granularity;
+        buf += granularity;
+    }
+}
+
+static void mirror_drain(MirrorBlockJob *s)
+{
+    while (s->in_flight > 0) {
+        qemu_coroutine_yield();
+    }
+}
+
+typedef struct {
+    int ret;
+} MirrorExitData;
+
+static void mirror_exit(BlockJob *job, void *opaque)
+{
+    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+    MirrorExitData *data = opaque;
+    AioContext *replace_aio_context = NULL;
+
+    if (s->to_replace) {
+        replace_aio_context = bdrv_get_aio_context(s->to_replace);
+        aio_context_acquire(replace_aio_context);
+    }
+
+    if (s->should_complete && data->ret == 0) {
+        BlockDriverState *to_replace = s->common.bs;
+        if (s->to_replace) {
+            to_replace = s->to_replace;
+        }
+        if (bdrv_get_flags(s->target) != bdrv_get_flags(to_replace)) {
+            bdrv_reopen(s->target, bdrv_get_flags(to_replace), NULL);
+        }
+        bdrv_swap(s->target, to_replace);
+        if (s->common.driver->job_type == BLOCK_JOB_TYPE_COMMIT) {
+            /* drop the bs loop chain formed by the swap: break the loop then
+             * trigger the unref from the top one */
+            BlockDriverState *p = s->base->backing_hd;
+            bdrv_set_backing_hd(s->base, NULL);
+            bdrv_unref(p);
+        }
+    }
+    if (s->to_replace) {
+        bdrv_op_unblock_all(s->to_replace, s->replace_blocker);
+        error_free(s->replace_blocker);
+        bdrv_unref(s->to_replace);
+    }
+    if (replace_aio_context) {
+        aio_context_release(replace_aio_context);
+    }
+    g_free(s->replaces);
+    bdrv_unref(s->target);
+    block_job_completed(&s->common, data->ret);
+    g_free(data);
+}
+
+static void coroutine_fn mirror_run(void *opaque)
+{
+    MirrorBlockJob *s = opaque;
+    MirrorExitData *data;
+    BlockDriverState *bs = s->common.bs;
+    int64_t sector_num, end, length;
+    uint64_t last_pause_ns;
+    BlockDriverInfo bdi;
+    char backing_filename[2]; /* we only need 2 characters because we are only
+                                 checking for a NULL string */
+    int ret = 0;
+    int n;
+
+    if (block_job_is_cancelled(&s->common)) {
+        goto immediate_exit;
+    }
+
+    s->bdev_length = bdrv_getlength(bs);
+    if (s->bdev_length < 0) {
+        ret = s->bdev_length;
+        goto immediate_exit;
+    } else if (s->bdev_length == 0) {
+        /* Report BLOCK_JOB_READY and wait for complete. */
+        block_job_event_ready(&s->common);
+        s->synced = true;
+        while (!block_job_is_cancelled(&s->common) && !s->should_complete) {
+            block_job_yield(&s->common);
+        }
+        s->common.cancelled = false;
+        goto immediate_exit;
+    }
+
+    length = DIV_ROUND_UP(s->bdev_length, s->granularity);
+    s->in_flight_bitmap = bitmap_new(length);
+
+    /* If we have no backing file yet in the destination, we cannot let
+     * the destination do COW.  Instead, we copy sectors around the
+     * dirty data if needed.  We need a bitmap to do that.
+     */
+    bdrv_get_backing_filename(s->target, backing_filename,
+                              sizeof(backing_filename));
+    if (backing_filename[0] && !s->target->backing_hd) {
+        ret = bdrv_get_info(s->target, &bdi);
+        if (ret < 0) {
+            goto immediate_exit;
+        }
+        if (s->granularity < bdi.cluster_size) {
+            s->buf_size = MAX(s->buf_size, bdi.cluster_size);
+            s->cow_bitmap = bitmap_new(length);
+        }
+    }
+
+    end = s->bdev_length / BDRV_SECTOR_SIZE;
+    s->buf = qemu_try_blockalign(bs, s->buf_size);
+    if (s->buf == NULL) {
+        ret = -ENOMEM;
+        goto immediate_exit;
+    }
+
+    mirror_free_init(s);
+
+    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+    if (!s->is_none_mode) {
+        /* First part, loop on the sectors and initialize the dirty bitmap.  */
+        BlockDriverState *base = s->base;
+        for (sector_num = 0; sector_num < end; ) {
+            /* Just to make sure we are not exceeding int limit. */
+            int nb_sectors = MIN(INT_MAX >> BDRV_SECTOR_BITS,
+                                 end - sector_num);
+            int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+
+            if (now - last_pause_ns > SLICE_TIME) {
+                last_pause_ns = now;
+                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
+            }
+
+            if (block_job_is_cancelled(&s->common)) {
+                goto immediate_exit;
+            }
+
+            ret = bdrv_is_allocated_above(bs, base, sector_num, nb_sectors, &n);
+
+            if (ret < 0) {
+                goto immediate_exit;
+            }
+
+            assert(n > 0);
+            if (ret == 1) {
+                bdrv_set_dirty_bitmap(s->dirty_bitmap, sector_num, n);
+            }
+            sector_num += n;
+        }
+    }
+
+    bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
+    for (;;) {
+        uint64_t delay_ns = 0;
+        int64_t cnt;
+        bool should_complete;
+
+        if (s->ret < 0) {
+            ret = s->ret;
+            goto immediate_exit;
+        }
+
+        cnt = bdrv_get_dirty_count(s->dirty_bitmap);
+        /* s->common.offset contains the number of bytes already processed so
+         * far, cnt is the number of dirty sectors remaining and
+         * s->sectors_in_flight is the number of sectors currently being
+         * processed; together those are the current total operation length */
+        s->common.len = s->common.offset +
+                        (cnt + s->sectors_in_flight) * BDRV_SECTOR_SIZE;
+
+        /* Note that even when no rate limit is applied we need to yield
+         * periodically with no pending I/O so that bdrv_drain_all() returns.
+         * We do so every SLICE_TIME nanoseconds, or when there is an error,
+         * or when the source is clean, whichever comes first.
+         */
+        if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < SLICE_TIME &&
+            s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
+            if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
+                (cnt == 0 && s->in_flight > 0)) {
+                trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
+                qemu_coroutine_yield();
+                continue;
+            } else if (cnt != 0) {
+                delay_ns = mirror_iteration(s);
+            }
+        }
+
+        should_complete = false;
+        if (s->in_flight == 0 && cnt == 0) {
+            trace_mirror_before_flush(s);
+            ret = bdrv_flush(s->target);
+            if (ret < 0) {
+                if (mirror_error_action(s, false, -ret) ==
+                    BLOCK_ERROR_ACTION_REPORT) {
+                    goto immediate_exit;
+                }
+            } else {
+                /* We're out of the streaming phase.  From now on, if the job
+                 * is cancelled we will actually complete all pending I/O and
+                 * report completion.  This way, block-job-cancel will leave
+                 * the target in a consistent state.
+                 */
+                if (!s->synced) {
+                    block_job_event_ready(&s->common);
+                    s->synced = true;
+                }
+
+                should_complete = s->should_complete ||
+                    block_job_is_cancelled(&s->common);
+                cnt = bdrv_get_dirty_count(s->dirty_bitmap);
+            }
+        }
+
+        if (cnt == 0 && should_complete) {
+            /* The dirty bitmap is not updated while operations are pending.
+             * If we're about to exit, wait for pending operations before
+             * calling bdrv_get_dirty_count(bs), or we may exit while the
+             * source has dirty data to copy!
+             *
+             * Note that I/O can be submitted by the guest while
+             * mirror_populate runs.
+             */
+            trace_mirror_before_drain(s, cnt);
+            bdrv_drain(bs);
+            cnt = bdrv_get_dirty_count(s->dirty_bitmap);
+        }
+
+        ret = 0;
+        trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
+        if (!s->synced) {
+            block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
+            if (block_job_is_cancelled(&s->common)) {
+                break;
+            }
+        } else if (!should_complete) {
+            delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
+            block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
+        } else if (cnt == 0) {
+            /* The two disks are in sync.  Exit and report successful
+             * completion.
+             */
+            assert(QLIST_EMPTY(&bs->tracked_requests));
+            s->common.cancelled = false;
+            break;
+        }
+        last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+    }
+
+immediate_exit:
+    if (s->in_flight > 0) {
+        /* We get here only if something went wrong.  Either the job failed,
+         * or it was cancelled prematurely so that we do not guarantee that
+         * the target is a copy of the source.
+         */
+        assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common)));
+        mirror_drain(s);
+    }
+
+    assert(s->in_flight == 0);
+    qemu_vfree(s->buf);
+    g_free(s->cow_bitmap);
+    g_free(s->in_flight_bitmap);
+    bdrv_release_dirty_bitmap(bs, s->dirty_bitmap);
+    bdrv_iostatus_disable(s->target);
+
+    data = g_malloc(sizeof(*data));
+    data->ret = ret;
+    block_job_defer_to_main_loop(&s->common, mirror_exit, data);
+}
+
+static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp)
+{
+    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+
+    if (speed < 0) {
+        error_setg(errp, QERR_INVALID_PARAMETER, "speed");
+        return;
+    }
+    ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
+}
+
+static void mirror_iostatus_reset(BlockJob *job)
+{
+    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+
+    bdrv_iostatus_reset(s->target);
+}
+
+static void mirror_complete(BlockJob *job, Error **errp)
+{
+    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+    Error *local_err = NULL;
+    int ret;
+
+    ret = bdrv_open_backing_file(s->target, NULL, &local_err);
+    if (ret < 0) {
+        error_propagate(errp, local_err);
+        return;
+    }
+    if (!s->synced) {
+        error_setg(errp, QERR_BLOCK_JOB_NOT_READY,
+                   bdrv_get_device_name(job->bs));
+        return;
+    }
+
+    /* check the target bs is not blocked and block all operations on it */
+    if (s->replaces) {
+        AioContext *replace_aio_context;
+
+        s->to_replace = check_to_replace_node(s->replaces, &local_err);
+        if (!s->to_replace) {
+            error_propagate(errp, local_err);
+            return;
+        }
+
+        replace_aio_context = bdrv_get_aio_context(s->to_replace);
+        aio_context_acquire(replace_aio_context);
+
+        error_setg(&s->replace_blocker,
+                   "block device is in use by block-job-complete");
+        bdrv_op_block_all(s->to_replace, s->replace_blocker);
+        bdrv_ref(s->to_replace);
+
+        aio_context_release(replace_aio_context);
+    }
+
+    s->should_complete = true;
+    block_job_enter(&s->common);
+}
+
+static const BlockJobDriver mirror_job_driver = {
+    .instance_size = sizeof(MirrorBlockJob),
+    .job_type      = BLOCK_JOB_TYPE_MIRROR,
+    .set_speed     = mirror_set_speed,
+    .iostatus_reset= mirror_iostatus_reset,
+    .complete      = mirror_complete,
+};
+
+static const BlockJobDriver commit_active_job_driver = {
+    .instance_size = sizeof(MirrorBlockJob),
+    .job_type      = BLOCK_JOB_TYPE_COMMIT,
+    .set_speed     = mirror_set_speed,
+    .iostatus_reset
+                   = mirror_iostatus_reset,
+    .complete      = mirror_complete,
+};
+
+static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
+                             const char *replaces,
+                             int64_t speed, uint32_t granularity,
+                             int64_t buf_size,
+                             BlockdevOnError on_source_error,
+                             BlockdevOnError on_target_error,
+                             bool unmap,
+                             BlockCompletionFunc *cb,
+                             void *opaque, Error **errp,
+                             const BlockJobDriver *driver,
+                             bool is_none_mode, BlockDriverState *base)
+{
+    MirrorBlockJob *s;
+
+    if (granularity == 0) {
+        granularity = bdrv_get_default_bitmap_granularity(target);
+    }
+
+    assert ((granularity & (granularity - 1)) == 0);
+
+    if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
+         on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
+        !bdrv_iostatus_is_enabled(bs)) {
+        error_setg(errp, QERR_INVALID_PARAMETER, "on-source-error");
+        return;
+    }
+
+    if (buf_size < 0) {
+        error_setg(errp, "Invalid parameter 'buf-size'");
+        return;
+    }
+
+    if (buf_size == 0) {
+        buf_size = DEFAULT_MIRROR_BUF_SIZE;
+    }
+
+    s = block_job_create(driver, bs, speed, cb, opaque, errp);
+    if (!s) {
+        return;
+    }
+
+    s->replaces = g_strdup(replaces);
+    s->on_source_error = on_source_error;
+    s->on_target_error = on_target_error;
+    s->target = target;
+    s->is_none_mode = is_none_mode;
+    s->base = base;
+    s->granularity = granularity;
+    s->buf_size = ROUND_UP(buf_size, granularity);
+    s->unmap = unmap;
+
+    s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
+    if (!s->dirty_bitmap) {
+        g_free(s->replaces);
+        block_job_release(bs);
+        return;
+    }
+    bdrv_set_enable_write_cache(s->target, true);
+    bdrv_set_on_error(s->target, on_target_error, on_target_error);
+    bdrv_iostatus_enable(s->target);
+    s->common.co = qemu_coroutine_create(mirror_run);
+    trace_mirror_start(bs, s, s->common.co, opaque);
+    qemu_coroutine_enter(s->common.co, s);
+}
+
+void mirror_start(BlockDriverState *bs, BlockDriverState *target,
+                  const char *replaces,
+                  int64_t speed, uint32_t granularity, int64_t buf_size,
+                  MirrorSyncMode mode, BlockdevOnError on_source_error,
+                  BlockdevOnError on_target_error,
+                  bool unmap,
+                  BlockCompletionFunc *cb,
+                  void *opaque, Error **errp)
+{
+    bool is_none_mode;
+    BlockDriverState *base;
+
+    if (mode == MIRROR_SYNC_MODE_INCREMENTAL) {
+        error_setg(errp, "Sync mode 'incremental' not supported");
+        return;
+    }
+    is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
+    base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL;
+    mirror_start_job(bs, target, replaces,
+                     speed, granularity, buf_size,
+                     on_source_error, on_target_error, unmap, cb, opaque, errp,
+                     &mirror_job_driver, is_none_mode, base);
+}
+
+void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
+                         int64_t speed,
+                         BlockdevOnError on_error,
+                         BlockCompletionFunc *cb,
+                         void *opaque, Error **errp)
+{
+    int64_t length, base_length;
+    int orig_base_flags;
+    int ret;
+    Error *local_err = NULL;
+
+    orig_base_flags = bdrv_get_flags(base);
+
+    if (bdrv_reopen(base, bs->open_flags, errp)) {
+        return;
+    }
+
+    length = bdrv_getlength(bs);
+    if (length < 0) {
+        error_setg_errno(errp, -length,
+                         "Unable to determine length of %s", bs->filename);
+        goto error_restore_flags;
+    }
+
+    base_length = bdrv_getlength(base);
+    if (base_length < 0) {
+        error_setg_errno(errp, -base_length,
+                         "Unable to determine length of %s", base->filename);
+        goto error_restore_flags;
+    }
+
+    if (length > base_length) {
+        ret = bdrv_truncate(base, length);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret,
+                            "Top image %s is larger than base image %s, and "
+                             "resize of base image failed",
+                             bs->filename, base->filename);
+            goto error_restore_flags;
+        }
+    }
+
+    bdrv_ref(base);
+    mirror_start_job(bs, base, NULL, speed, 0, 0,
+                     on_error, on_error, false, cb, opaque, &local_err,
+                     &commit_active_job_driver, false, base);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto error_restore_flags;
+    }
+
+    return;
+
+error_restore_flags:
+    /* ignore error and errp for bdrv_reopen, because we want to propagate
+     * the original error */
+    bdrv_reopen(base, orig_base_flags, NULL);
+    return;
+}