diff --git a/block/backup.c b/block/backup.c
index 00f4f8af53..a5b8e04c9c 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -2,6 +2,7 @@
  * QEMU backup
  *
  * Copyright (C) 2013 Proxmox Server Solutions
+ * Copyright (c) 2019 Virtuozzo International GmbH. All rights reserved.
  *
  * Authors:
  *  Dietmar Maurer (dietmar@proxmox.com)
@@ -26,14 +27,9 @@
 #include "qemu/bitmap.h"
 #include "qemu/error-report.h"
 
-#define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
+#include "block/backup-top.h"
 
-typedef struct CowRequest {
-    int64_t start_byte;
-    int64_t end_byte;
-    QLIST_ENTRY(CowRequest) list;
-    CoQueue wait_queue; /* coroutines blocked on this request */
-} CowRequest;
+#define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
 
 typedef struct BackupBlockJob {
     BlockJob common;
@@ -43,13 +39,10 @@ typedef struct BackupBlockJob {
     MirrorSyncMode sync_mode;
     BlockdevOnError on_source_error;
     BlockdevOnError on_target_error;
-    CoRwlock flush_rwlock;
     uint64_t len;
     uint64_t bytes_read;
     int64_t cluster_size;
     bool compress;
-    NotifierWithReturn before_write;
-    QLIST_HEAD(, CowRequest) inflight_reqs;
 
     HBitmap *copy_bitmap;
     bool use_copy_range;
@@ -60,56 +53,17 @@ typedef struct BackupBlockJob {
 
 static const BlockJobDriver backup_job_driver;
 
-/* See if in-flight requests overlap and wait for them to complete */
-static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job,
-                                                       int64_t start,
-                                                       int64_t end)
-{
-    CowRequest *req;
-    bool retry;
-
-    do {
-        retry = false;
-        QLIST_FOREACH(req, &job->inflight_reqs, list) {
-            if (end > req->start_byte && start < req->end_byte) {
-                qemu_co_queue_wait(&req->wait_queue, NULL);
-                retry = true;
-                break;
-            }
-        }
-    } while (retry);
-}
-
-/* Keep track of an in-flight request */
-static void cow_request_begin(CowRequest *req, BackupBlockJob *job,
-                              int64_t start, int64_t end)
-{
-    req->start_byte = start;
-    req->end_byte = end;
-    qemu_co_queue_init(&req->wait_queue);
-    QLIST_INSERT_HEAD(&job->inflight_reqs, req, list);
-}
-
-/* Forget about a completed request */
-static void cow_request_end(CowRequest *req)
-{
-    QLIST_REMOVE(req, list);
-    qemu_co_queue_restart_all(&req->wait_queue);
-}
-
 /* Copy range to target with a bounce buffer and return the bytes copied. If
  * error occurred, return a negative error number */
 static int coroutine_fn backup_cow_with_bounce_buffer(BackupBlockJob *job,
                                                       int64_t start,
                                                       int64_t end,
-                                                      bool is_write_notifier,
                                                       bool *error_is_read,
                                                       void **bounce_buffer)
 {
     int ret;
     BlockBackend *blk = job->common.blk;
     int nbytes;
-    int read_flags = is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0;
     int write_flags = job->serialize_target_writes ? BDRV_REQ_SERIALISING : 0;
 
     assert(QEMU_IS_ALIGNED(start, job->cluster_size));
@@ -119,7 +73,7 @@ static int coroutine_fn backup_cow_with_bounce_buffer(BackupBlockJob *job,
         *bounce_buffer = blk_blockalign(blk, job->cluster_size);
     }
 
-    ret = blk_co_pread(blk, start, nbytes, *bounce_buffer, read_flags);
+    ret = blk_co_pread(blk, start, nbytes, *bounce_buffer, 0);
     if (ret < 0) {
         trace_backup_do_cow_read_fail(job, start, ret);
         if (error_is_read) {
@@ -154,15 +108,12 @@ fail:
 /* Copy range to target and return the bytes copied. If error occurred, return a
  * negative error number. */
 static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job,
-                                                int64_t start,
-                                                int64_t end,
-                                                bool is_write_notifier)
+                                                int64_t start, int64_t end)
 {
     int ret;
     int nr_clusters;
     BlockBackend *blk = job->common.blk;
     int nbytes;
-    int read_flags = is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0;
     int write_flags = job->serialize_target_writes ? BDRV_REQ_SERIALISING : 0;
 
     assert(QEMU_IS_ALIGNED(job->copy_range_size, job->cluster_size));
@@ -171,7 +122,7 @@ static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job,
     nr_clusters = DIV_ROUND_UP(nbytes, job->cluster_size);
     hbitmap_reset(job->copy_bitmap, start, job->cluster_size * nr_clusters);
     ret = blk_co_copy_range(blk, start, job->target, start, nbytes,
-                            read_flags, write_flags);
+                            0, write_flags);
     if (ret < 0) {
         trace_backup_do_cow_copy_range_fail(job, start, ret);
         hbitmap_set(job->copy_bitmap, start, job->cluster_size * nr_clusters);
@@ -183,24 +134,17 @@ static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job,
 
 static int coroutine_fn backup_do_cow(BackupBlockJob *job,
                                       int64_t offset, uint64_t bytes,
-                                      bool *error_is_read,
-                                      bool is_write_notifier)
+                                      bool *error_is_read)
 {
-    CowRequest cow_request;
     int ret = 0;
     int64_t start, end; /* bytes */
     void *bounce_buffer = NULL;
 
-    qemu_co_rwlock_rdlock(&job->flush_rwlock);
-
     start = QEMU_ALIGN_DOWN(offset, job->cluster_size);
     end = QEMU_ALIGN_UP(bytes + offset, job->cluster_size);
 
     trace_backup_do_cow_enter(job, start, offset, bytes);
 
-    wait_for_overlapping_requests(job, start, end);
-    cow_request_begin(&cow_request, job, start, end);
-
     while (start < end) {
         if (!hbitmap_get(job->copy_bitmap, start)) {
             trace_backup_do_cow_skip(job, start);
@@ -211,13 +155,13 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
         trace_backup_do_cow_process(job, start);
 
         if (job->use_copy_range) {
-            ret = backup_cow_with_offload(job, start, end, is_write_notifier);
+            ret = backup_cow_with_offload(job, start, end);
             if (ret < 0) {
                 job->use_copy_range = false;
             }
         }
         if (!job->use_copy_range) {
-            ret = backup_cow_with_bounce_buffer(job, start, end, is_write_notifier,
+            ret = backup_cow_with_bounce_buffer(job, start, end,
                                                 error_is_read, &bounce_buffer);
         }
         if (ret < 0) {
@@ -237,29 +181,11 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
         qemu_vfree(bounce_buffer);
     }
 
-    cow_request_end(&cow_request);
-
     trace_backup_do_cow_return(job, offset, bytes, ret);
 
-    qemu_co_rwlock_unlock(&job->flush_rwlock);
-
     return ret;
 }
 
-static int coroutine_fn backup_before_write_notify(
-        NotifierWithReturn *notifier,
-        void *opaque)
-{
-    BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write);
-    BdrvTrackedRequest *req = opaque;
-
-    assert(req->bs == blk_bs(job->common.blk));
-    assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE));
-    assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE));
-
-    return backup_do_cow(job, req->offset, req->bytes, NULL, true);
-}
-
 static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret)
 {
     BdrvDirtyBitmap *bm;
@@ -295,14 +221,30 @@ static void backup_abort(Job *job)
 static void backup_clean(Job *job)
 {
     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
+    BlockJob *bjob = &s->common;
+    BlockDriverState *backup_top = blk_bs(s->common.blk);
+    BlockDriverState *src = backup_top->backing->bs;
+
     assert(s->target);
     blk_unref(s->target);
     s->target = NULL;
 
+    bdrv_ref(backup_top);
+    bdrv_ref(src);
+
     if (s->copy_bitmap) {
         hbitmap_free(s->copy_bitmap);
         s->copy_bitmap = NULL;
     }
+
+    bdrv_backup_top_drop(backup_top);
+
+    blk_remove_bs(bjob->blk);
+    blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
+    blk_insert_bs(bjob->blk, backup_top, &error_abort);
+
+    bdrv_unref(src);
+    bdrv_unref(backup_top);
 }
 
 void backup_do_checkpoint(BlockJob *job, Error **errp)
@@ -391,28 +333,41 @@ static int coroutine_fn backup_loop(BackupBlockJob *job)
     int64_t offset;
     HBitmapIter hbi;
     BlockDriverState *bs = blk_bs(job->common.blk);
+    void *lock;
 
     hbitmap_iter_init(&hbi, job->copy_bitmap, 0);
     while ((offset = hbitmap_iter_next(&hbi)) != -1) {
+        lock = bdrv_co_try_lock(backing_bs(blk_bs(job->common.blk)), offset,
+                                job->cluster_size);
+        /*
+         * Dirty bit is set, which means that there are no in-flight
+         * write requests on this area. We must succeed.
+         */
+        assert(lock);
+
         if (job->sync_mode == MIRROR_SYNC_MODE_TOP &&
             bdrv_is_unallocated_range(bs, offset, job->cluster_size))
         {
             hbitmap_reset(job->copy_bitmap, offset, job->cluster_size);
+            bdrv_co_unlock(lock);
             continue;
         }
 
         do {
             if (yield_and_check(job)) {
+                bdrv_co_unlock(lock);
                 return 0;
             }
-            ret = backup_do_cow(job, offset,
-                                job->cluster_size, &error_is_read, false);
+            ret = backup_do_cow(job, offset, job->cluster_size, &error_is_read);
             if (ret < 0 && backup_error_action(job, error_is_read, -ret) ==
                            BLOCK_ERROR_ACTION_REPORT)
             {
+                bdrv_co_unlock(lock);
                 return ret;
             }
         } while (ret < 0);
+
+        bdrv_co_unlock(lock);
     }
 
     return 0;
@@ -444,12 +399,8 @@ static void backup_incremental_init_copy_bitmap(BackupBlockJob *job)
 static int coroutine_fn backup_run(Job *job, Error **errp)
 {
     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
-    BlockDriverState *bs = blk_bs(s->common.blk);
     int ret = 0;
 
-    QLIST_INIT(&s->inflight_reqs);
-    qemu_co_rwlock_init(&s->flush_rwlock);
-
     job_progress_set_remaining(job, s->len);
 
     if (s->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
@@ -458,27 +409,20 @@ static int coroutine_fn backup_run(Job *job, Error **errp)
         hbitmap_set(s->copy_bitmap, 0, s->len);
     }
 
-    s->before_write.notify = backup_before_write_notify;
-    bdrv_add_before_write_notifier(bs, &s->before_write);
-
     if (s->sync_mode == MIRROR_SYNC_MODE_NONE) {
         /* All bits are set in copy_bitmap to allow any cluster to be copied.
          * This does not actually require them to be copied. */
         while (!job_is_cancelled(job)) {
-            /* Yield until the job is cancelled.  We just let our before_write
-             * notify callback service CoW requests. */
+            /*
+             * Yield until the job is cancelled.  We just let our backup-top
+             * filter driver service CbW requests.
+             */
             job_yield(job);
         }
     } else {
         ret = backup_loop(s);
     }
 
-    notifier_with_return_remove(&s->before_write);
-
-    /* wait until pending backup_do_cow() calls have completed */
-    qemu_co_rwlock_wrlock(&s->flush_rwlock);
-    qemu_co_rwlock_unlock(&s->flush_rwlock);
-
     return ret;
 }
 
@@ -533,6 +477,11 @@ static int64_t backup_calculate_cluster_size(BlockDriverState *target,
     return MAX(BACKUP_CLUSTER_SIZE_DEFAULT, bdi.cluster_size);
 }
 
+static void backup_top_progress(uint64_t done, void *opaque)
+{
+    job_progress_update((Job *)opaque, done);
+}
+
 BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *target, int64_t speed,
                   MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
@@ -548,6 +497,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     int ret;
     int64_t cluster_size;
     HBitmap *copy_bitmap = NULL;
+    BlockDriverState *backup_top = NULL;
 
     assert(bs);
     assert(target);
@@ -616,8 +566,13 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
 
     copy_bitmap = hbitmap_alloc(len, ctz32(cluster_size));
 
+    backup_top = bdrv_backup_top_append(bs, target, copy_bitmap, errp);
+    if (!backup_top) {
+        goto error;
+    }
+
     /* job->len is fixed, so we can't allow resize */
-    job = block_job_create(job_id, &backup_job_driver, txn, bs,
+    job = block_job_create(job_id, &backup_job_driver, txn, backup_top,
                            BLK_PERM_CONSISTENT_READ,
                            BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE |
                            BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD,
@@ -626,6 +581,9 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         goto error;
     }
 
+    bdrv_backup_top_set_progress_callback(backup_top, backup_top_progress,
+                                          &job->common.job);
+
     /* The target must match the source in size, so no resize here either */
     job->target = blk_new(BLK_PERM_WRITE,
                           BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE |
@@ -662,10 +620,6 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     return &job->common;
 
  error:
-    if (copy_bitmap) {
-        assert(!job || !job->copy_bitmap);
-        hbitmap_free(copy_bitmap);
-    }
     if (sync_bitmap) {
         bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL);
     }
@@ -673,6 +627,13 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         backup_clean(&job->common.job);
         job_early_fail(&job->common.job);
     }
+    if (backup_top) {
+        bdrv_backup_top_drop(backup_top);
+    }
+    if (copy_bitmap) {
+        assert(!job || !job->copy_bitmap);
+        hbitmap_free(copy_bitmap);
+    }
 
     return NULL;
 }
diff --git a/tests/qemu-iotests/056 b/tests/qemu-iotests/056
index f40fc11a09..d3e6fe4b11 100755
--- a/tests/qemu-iotests/056
+++ b/tests/qemu-iotests/056
@@ -214,7 +214,7 @@ class BackupTest(iotests.QMPTestCase):
         res = self.vm.qmp('query-block-jobs')
         self.assert_qmp(res, 'return[0]/status', 'concluded')
         # Leave zombie job un-dismissed, observe a failure:
-        res = self.qmp_backup_and_wait(serror="Node 'drive0' is busy: block device is in use by block job: backup",
+        res = self.qmp_backup_and_wait(serror='Failed to get "write" lock',
                                        device='drive0', format=iotests.imgfmt,
                                        sync='full', target=self.dest_img,
                                        auto_dismiss=False)
diff --git a/tests/qemu-iotests/129 b/tests/qemu-iotests/129
index 9e87e1c8d9..d719492deb 100755
--- a/tests/qemu-iotests/129
+++ b/tests/qemu-iotests/129
@@ -66,7 +66,6 @@ class TestStopWithBlockJob(iotests.QMPTestCase):
         result = self.vm.qmp("stop")
         self.assert_qmp(result, 'return', {})
         result = self.vm.qmp("query-block-jobs")
-        self.assert_qmp(result, 'return[0]/busy', True)
         self.assert_qmp(result, 'return[0]/ready', False)
 
     def test_drive_mirror(self):
diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out
index 41c7291258..a2645bea1a 100644
--- a/tests/qemu-iotests/141.out
+++ b/tests/qemu-iotests/141.out
@@ -11,7 +11,7 @@ Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
 {"return": {}}
-{"error": {"class": "GenericError", "desc": "Node drv0 is in use"}}
+{"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: node is used as backing hd of 'NODE_NAME'"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "aborting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 0, "speed": 0, "type": "backup"}}
