diff --git a/qapi/block-core.json b/qapi/block-core.json
index 943df1926a..0fb527a9a1 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2202,6 +2202,54 @@
       { 'command': 'block-dirty-bitmap-merge',
         'data': 'BlockDirtyBitmapMerge' }
 
+##
+# @BitmapPattern:
+#
+# An enumeration of possible patterns that can be written into a bitmap.
+#
+# @allocation-top: The allocation status of the top layer
+#                  of the attached storage node.
+#
+# Since: 5.0
+##
+{ 'enum': 'BitmapPattern',
+  'data': ['allocation-top'] }
+
+##
+# @BlockDirtyBitmapPopulate:
+#
+# @job-id: identifier for the newly-created block job.
+#
+# @pattern: What pattern should be written into the bitmap?
+#
+# @on-error: the action to take if an error is encountered on a bitmap's
+#            attached node, default 'report'.
+#            'stop' and 'enospc' can only be used if the block device supports
+#            io-status (see BlockInfo).
+#
+# @auto-finalize: When false, this job will wait in a PENDING state after it has
+#                 finished its work, waiting for @block-job-finalize before
+#                 making any block graph changes.
+#                 When true, this job will automatically
+#                 perform its abort or commit actions.
+#                 Defaults to true.
+#
+# @auto-dismiss: When false, this job will wait in a CONCLUDED state after it
+#                has completely ceased all work, and awaits @block-job-dismiss.
+#                When true, this job will automatically disappear from the query
+#                list without user intervention.
+#                Defaults to true.
+#
+# Since: 5.0
+##
+{ 'struct': 'BlockDirtyBitmapPopulate',
+  'base': 'BlockDirtyBitmap',
+  'data': { 'job-id': 'str',
+            'pattern': 'BitmapPattern',
+            '*on-error': 'BlockdevOnError',
+            '*auto-finalize': 'bool',
+            '*auto-dismiss': 'bool' } }
+
 ##
 # @BlockDirtyBitmapSha256:
 #
diff --git a/qapi/job.json b/qapi/job.json
index 5e658281f5..5f496d4630 100644
--- a/qapi/job.json
+++ b/qapi/job.json
@@ -22,7 +22,7 @@
 # Since: 1.7
 ##
 { 'enum': 'JobType',
-  'data': ['commit', 'stream', 'mirror', 'backup', 'create'] }
+  'data': ['commit', 'stream', 'mirror', 'backup', 'create', 'bitmap-populate'] }
 
 ##
 # @JobStatus:
diff --git a/include/block/block_int.h b/include/block/block_int.h
index df6d0273d6..eb68a5639a 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1222,6 +1222,27 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                             BlockCompletionFunc *cb, void *opaque,
                             JobTxn *txn, Error **errp);
 
+/*
+ * bitpop_job_create: Create a new bitmap population job.
+ *
+ * @job_id: The id of the newly-created job.
+ * @bs: Block device associated with the @target_bitmap.
+ * @target_bitmap: The bitmap to populate.
+ * @on_error: What to do if an error on @bs is encountered.
+ * @creation_flags: Flags that control the behavior of the Job lifetime.
+ *                  See @BlockJobCreateFlags
+ * @cb: Completion function for the job.
+ * @opaque: Opaque pointer value passed to @cb.
+ * @txn: Transaction that this job is part of (may be NULL).
+ */
+BlockJob *bitpop_job_create(const char *job_id, BlockDriverState *bs,
+                            BdrvDirtyBitmap *target_bitmap,
+                            BitmapPattern pattern,
+                            BlockdevOnError on_error,
+                            int creation_flags,
+                            BlockCompletionFunc *cb, void *opaque,
+                            JobTxn *txn, Error **errp);
+
 BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
                                   const char *child_name,
                                   const BdrvChildRole *child_role,
diff --git a/block/bitmap-alloc.c b/block/bitmap-alloc.c
new file mode 100644
index 0000000000..47d542dc12
--- /dev/null
+++ b/block/bitmap-alloc.c
@@ -0,0 +1,207 @@
+/*
+ * Async Dirty Bitmap Populator
+ *
+ * Copyright (C) 2020 Red Hat, Inc.
+ *
+ * Authors:
+ *  John Snow <jsnow@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include "trace.h"
+#include "block/block.h"
+#include "block/block_int.h"
+#include "block/blockjob_int.h"
+#include "block/block_backup.h"
+#include "block/block-copy.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qerror.h"
+#include "qemu/ratelimit.h"
+#include "qemu/cutils.h"
+#include "sysemu/block-backend.h"
+#include "qemu/bitmap.h"
+#include "qemu/error-report.h"
+
+typedef struct BitpopBlockJob {
+    BlockJob common;
+    BlockDriverState *bs;
+    BdrvDirtyBitmap *target_bitmap;
+    BdrvDirtyBitmap *new_bitmap;
+    BlockdevOnError on_error;
+    uint64_t len;
+} BitpopBlockJob;
+
+static const BlockJobDriver bitpop_job_driver;
+
+static void bitpop_commit(Job *job)
+{
+    BitpopBlockJob *s = container_of(job, BitpopBlockJob, common.job);
+
+    bdrv_dirty_bitmap_merge_internal(s->target_bitmap, s->new_bitmap,
+                                     NULL, true);
+}
+
+/* no abort needed; just clean without committing. */
+
+static void bitpop_clean(Job *job)
+{
+    BitpopBlockJob *s = container_of(job, BitpopBlockJob, common.job);
+
+    bdrv_release_dirty_bitmap(s->new_bitmap);
+    bdrv_dirty_bitmap_set_busy(s->target_bitmap, false);
+}
+
+static BlockErrorAction bitpop_error_action(BitpopBlockJob *job, int error)
+{
+    return block_job_error_action(&job->common, job->on_error, true, error);
+}
+
+static bool coroutine_fn yield_and_check(Job *job)
+{
+    if (job_is_cancelled(job)) {
+        return true;
+    }
+
+    job_sleep_ns(job, 0);
+
+    if (job_is_cancelled(job)) {
+        return true;
+    }
+
+    return false;
+}
+
+static int coroutine_fn bitpop_run(Job *job, Error **errp)
+{
+    BitpopBlockJob *s = container_of(job, BitpopBlockJob, common.job);
+    int ret = 0;
+    int64_t offset;
+    int64_t count;
+    int64_t bytes;
+
+    for (offset = 0; offset < s->len; ) {
+        if (yield_and_check(job)) {
+            ret = -ECANCELED;
+            break;
+        }
+
+        bytes = s->len - offset;
+        ret = bdrv_is_allocated(s->bs, offset, bytes, &count);
+        if (ret < 0) {
+            if (bitpop_error_action(s, -ret) == BLOCK_ERROR_ACTION_REPORT) {
+                break;
+            }
+            continue;
+        }
+
+        if (!count) {
+            ret = 0;
+            break;
+        }
+
+        if (ret) {
+            bdrv_set_dirty_bitmap(s->new_bitmap, offset, count);
+            ret = 0;
+        }
+
+        job_progress_update(job, count);
+        offset += count;
+    }
+
+    return ret;
+}
+
+static const BlockJobDriver bitpop_job_driver = {
+    .job_driver = {
+        .instance_size          = sizeof(BitpopBlockJob),
+        .job_type               = JOB_TYPE_BITMAP_POPULATE,
+        .free                   = block_job_free,
+        .user_resume            = block_job_user_resume,
+        .run                    = bitpop_run,
+        .commit                 = bitpop_commit,
+        .clean                  = bitpop_clean,
+    }
+};
+
+
+BlockJob *bitpop_job_create(
+    const char *job_id,
+    BlockDriverState *bs,
+    BdrvDirtyBitmap *target_bitmap,
+    BitmapPattern pattern,
+    BlockdevOnError on_error,
+    int creation_flags,
+    BlockCompletionFunc *cb,
+    void *opaque,
+    JobTxn *txn,
+    Error **errp)
+{
+    int64_t len;
+    BitpopBlockJob *job = NULL;
+    int64_t cluster_size;
+    BdrvDirtyBitmap *new_bitmap = NULL;
+
+    assert(bs);
+    assert(target_bitmap);
+
+    if (!bdrv_is_inserted(bs)) {
+        error_setg(errp, "Device is not inserted: %s",
+                   bdrv_get_device_name(bs));
+        return NULL;
+    }
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
+        return NULL;
+    }
+
+    if (bdrv_dirty_bitmap_check(target_bitmap, BDRV_BITMAP_DEFAULT, errp)) {
+        return NULL;
+    }
+
+    if (pattern != BITMAP_PATTERN_ALLOCATION_TOP) {
+        error_setg(errp, "Unrecognized bitmap pattern");
+        return NULL;
+    }
+
+    len = bdrv_getlength(bs);
+    if (len < 0) {
+        error_setg_errno(errp, -len, "unable to get length for '%s'",
+                         bdrv_get_device_name(bs));
+        return NULL;
+    }
+
+    /* NB: new bitmap is anonymous and enabled */
+    cluster_size = bdrv_dirty_bitmap_granularity(target_bitmap);
+    new_bitmap = bdrv_create_dirty_bitmap(bs, cluster_size, NULL, errp);
+    if (!new_bitmap) {
+        return NULL;
+    }
+
+    /* Take ownership; we reserve the right to write into this on-commit. */
+    bdrv_dirty_bitmap_set_busy(target_bitmap, true);
+
+    job = block_job_create(job_id, &bitpop_job_driver, txn, bs,
+                           BLK_PERM_CONSISTENT_READ,
+                           BLK_PERM_ALL & ~BLK_PERM_RESIZE,
+                           0, creation_flags,
+                           cb, opaque, errp);
+    if (!job) {
+        bdrv_dirty_bitmap_set_busy(target_bitmap, false);
+        bdrv_release_dirty_bitmap(new_bitmap);
+        return NULL;
+    }
+
+    job->bs = bs;
+    job->on_error = on_error;
+    job->target_bitmap = target_bitmap;
+    job->new_bitmap = new_bitmap;
+    job->len = len;
+    job_progress_set_remaining(&job->common.job, job->len);
+
+    return &job->common;
+}
diff --git a/blockjob.c b/blockjob.c
index 2affa1844d..991d9167a2 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -56,7 +56,8 @@ static bool is_block_job(Job *job)
     return job_type(job) == JOB_TYPE_BACKUP ||
            job_type(job) == JOB_TYPE_COMMIT ||
            job_type(job) == JOB_TYPE_MIRROR ||
-           job_type(job) == JOB_TYPE_STREAM;
+           job_type(job) == JOB_TYPE_STREAM ||
+           job_type(job) == JOB_TYPE_BITMAP_POPULATE;
 }
 
 BlockJob *block_job_next(BlockJob *bjob)
diff --git a/block/Makefile.objs b/block/Makefile.objs
index 3635b6b4c1..87357529f3 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -36,6 +36,7 @@ block-obj-$(CONFIG_LIBSSH) += ssh.o
 block-obj-y += accounting.o dirty-bitmap.o
 block-obj-y += write-threshold.o
 block-obj-y += backup.o
+block-obj-y += bitmap-alloc.o
 block-obj-$(CONFIG_REPLICATION) += replication.o
 block-obj-y += throttle.o copy-on-read.o
 block-obj-y += block-copy.o
