Merge remote-tracking branch 'jtc/tags/block-pull-request' into staging

# gpg: Signature made Tue 15 Nov 2016 04:10:29 AM GMT
# gpg:                using RSA key 0xBDBE7B27C0DE3057
# gpg: Good signature from "Jeffrey Cody <jcody@redhat.com>"
# gpg:                 aka "Jeffrey Cody <jeff@codyprime.org>"
# gpg:                 aka "Jeffrey Cody <codyprime@gmail.com>"
# Primary key fingerprint: 9957 4B4D 3474 90E7 9D98  D624 BDBE 7B27 C0DE 3057

* jtc/tags/block-pull-request:
  mirror: do not flush every time the disks are synced
  block/curl: Do not wait for data beyond EOF
  block/curl: Remember all sockets
  block/curl: Fix return value from curl_read_cb
  block/curl: Use BDRV_SECTOR_SIZE
  block/curl: Drop TFTP "support"
  qemu-iotests: avoid spurious failure on test 109
  iotests: add transactional failure race test
  blockjob: refactor backup_start as backup_job_create
  blockjob: add block_job_start
  blockjob: add .start field
  blockjob: add .clean property
  blockjob: fix dead pointer in txn list

Message-id: 1479183291-14086-1-git-send-email-jcody@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

19 files changed, 339 insertions, 189 deletions

diff --git a/block/backup.c b/block/backup.c
index 7b5d8a3757..ea38733849 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -242,6 +242,14 @@ static void backup_abort(BlockJob *job)
     }
 }
 
+static void backup_clean(BlockJob *job)
+{
+    BackupBlockJob *s = container_of(job, BackupBlockJob, common);
+    assert(s->target);
+    blk_unref(s->target);
+    s->target = NULL;
+}
+
 static void backup_attached_aio_context(BlockJob *job, AioContext *aio_context)
 {
     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
@@ -315,16 +323,6 @@ static void backup_drain(BlockJob *job)
     }
 }
 
-static const BlockJobDriver backup_job_driver = {
-    .instance_size          = sizeof(BackupBlockJob),
-    .job_type               = BLOCK_JOB_TYPE_BACKUP,
-    .set_speed              = backup_set_speed,
-    .commit                 = backup_commit,
-    .abort                  = backup_abort,
-    .attached_aio_context   = backup_attached_aio_context,
-    .drain                  = backup_drain,
-};
-
 static BlockErrorAction backup_error_action(BackupBlockJob *job,
                                             bool read, int error)
 {
@@ -343,12 +341,8 @@ typedef struct {
 
 static void backup_complete(BlockJob *job, void *opaque)
 {
-    BackupBlockJob *s = container_of(job, BackupBlockJob, common);
     BackupCompleteData *data = opaque;
 
-    blk_unref(s->target);
-    s->target = NULL;
-
     block_job_completed(job, data->ret);
     g_free(data);
 }
@@ -537,7 +531,19 @@ static void coroutine_fn backup_run(void *opaque)
     block_job_defer_to_main_loop(&job->common, backup_complete, data);
 }
 
-void backup_start(const char *job_id, BlockDriverState *bs,
+static const BlockJobDriver backup_job_driver = {
+    .instance_size          = sizeof(BackupBlockJob),
+    .job_type               = BLOCK_JOB_TYPE_BACKUP,
+    .start                  = backup_run,
+    .set_speed              = backup_set_speed,
+    .commit                 = backup_commit,
+    .abort                  = backup_abort,
+    .clean                  = backup_clean,
+    .attached_aio_context   = backup_attached_aio_context,
+    .drain                  = backup_drain,
+};
+
+BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *target, int64_t speed,
                   MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
                   bool compress,
@@ -557,52 +563,52 @@ void backup_start(const char *job_id, BlockDriverState *bs,
 
     if (bs == target) {
         error_setg(errp, "Source and target cannot be the same");
-        return;
+        return NULL;
     }
 
     if (!bdrv_is_inserted(bs)) {
         error_setg(errp, "Device is not inserted: %s",
                    bdrv_get_device_name(bs));
-        return;
+        return NULL;
     }
 
     if (!bdrv_is_inserted(target)) {
         error_setg(errp, "Device is not inserted: %s",
                    bdrv_get_device_name(target));
-        return;
+        return NULL;
     }
 
     if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) {
         error_setg(errp, "Compression is not supported for this drive %s",
                    bdrv_get_device_name(target));
-        return;
+        return NULL;
     }
 
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
-        return;
+        return NULL;
     }
 
     if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
-        return;
+        return NULL;
     }
 
     if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
         if (!sync_bitmap) {
             error_setg(errp, "must provide a valid bitmap name for "
                              "\"incremental\" sync mode");
-            return;
+            return NULL;
         }
 
         /* Create a new bitmap, and freeze/disable this one. */
         if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) {
-            return;
+            return NULL;
         }
     } else if (sync_bitmap) {
         error_setg(errp,
                    "a sync_bitmap was provided to backup_run, "
                    "but received an incompatible sync_mode (%s)",
                    MirrorSyncMode_lookup[sync_mode]);
-        return;
+        return NULL;
     }
 
     len = bdrv_getlength(bs);
@@ -648,17 +654,18 @@ void backup_start(const char *job_id, BlockDriverState *bs,
 
     block_job_add_bdrv(&job->common, target);
     job->common.len = len;
-    job->common.co = qemu_coroutine_create(backup_run, job);
     block_job_txn_add_job(txn, &job->common);
-    qemu_coroutine_enter(job->common.co);
-    return;
+
+    return &job->common;
 
  error:
     if (sync_bitmap) {
         bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL);
     }
     if (job) {
-        blk_unref(job->target);
+        backup_clean(&job->common);
         block_job_unref(&job->common);
     }
+
+    return NULL;
 }
diff --git a/block/commit.c b/block/commit.c
index e1eda8908b..c284e8535d 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -205,6 +205,7 @@ static const BlockJobDriver commit_job_driver = {
     .instance_size = sizeof(CommitBlockJob),
     .job_type      = BLOCK_JOB_TYPE_COMMIT,
     .set_speed     = commit_set_speed,
+    .start         = commit_run,
 };
 
 void commit_start(const char *job_id, BlockDriverState *bs,
@@ -288,10 +289,9 @@ void commit_start(const char *job_id, BlockDriverState *bs,
     s->backing_file_str = g_strdup(backing_file_str);
 
     s->on_error = on_error;
-    s->common.co = qemu_coroutine_create(commit_run, s);
 
-    trace_commit_start(bs, base, top, s, s->common.co);
-    qemu_coroutine_enter(s->common.co);
+    trace_commit_start(bs, base, top, s);
+    block_job_start(&s->common);
 }
 
 
diff --git a/block/curl.c b/block/curl.c
index e5eaa7ba0a..0404c1b5fa 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -68,12 +68,10 @@ static CURLMcode __curl_multi_socket_action(CURLM *multi_handle,
 #endif
 
 #define PROTOCOLS (CURLPROTO_HTTP | CURLPROTO_HTTPS | \
-                   CURLPROTO_FTP | CURLPROTO_FTPS | \
-                   CURLPROTO_TFTP)
+                   CURLPROTO_FTP | CURLPROTO_FTPS)
 
 #define CURL_NUM_STATES 8
 #define CURL_NUM_ACB    8
-#define SECTOR_SIZE     512
 #define READ_AHEAD_DEFAULT (256 * 1024)
 #define CURL_TIMEOUT_DEFAULT 5
 #define CURL_TIMEOUT_MAX 10000
@@ -105,12 +103,17 @@ typedef struct CURLAIOCB {
     size_t end;
 } CURLAIOCB;
 
+typedef struct CURLSocket {
+    int fd;
+    QLIST_ENTRY(CURLSocket) next;
+} CURLSocket;
+
 typedef struct CURLState
 {
     struct BDRVCURLState *s;
     CURLAIOCB *acb[CURL_NUM_ACB];
     CURL *curl;
-    curl_socket_t sock_fd;
+    QLIST_HEAD(, CURLSocket) sockets;
     char *orig_buf;
     size_t buf_start;
     size_t buf_off;
@@ -164,10 +167,27 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
 {
     BDRVCURLState *s;
     CURLState *state = NULL;
+    CURLSocket *socket;
+
     curl_easy_getinfo(curl, CURLINFO_PRIVATE, (char **)&state);
-    state->sock_fd = fd;
     s = state->s;
 
+    QLIST_FOREACH(socket, &state->sockets, next) {
+        if (socket->fd == fd) {
+            if (action == CURL_POLL_REMOVE) {
+                QLIST_REMOVE(socket, next);
+                g_free(socket);
+            }
+            break;
+        }
+    }
+    if (!socket) {
+        socket = g_new0(CURLSocket, 1);
+        socket->fd = fd;
+        QLIST_INSERT_HEAD(&state->sockets, socket, next);
+    }
+    socket = NULL;
+
     DPRINTF("CURL (AIO): Sock action %d on fd %d\n", action, (int)fd);
     switch (action) {
         case CURL_POLL_IN:
@@ -213,12 +233,13 @@ static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
 
     DPRINTF("CURL: Just reading %zd bytes\n", realsize);
 
-    if (!s || !s->orig_buf)
-        return 0;
+    if (!s || !s->orig_buf) {
+        goto read_end;
+    }
 
     if (s->buf_off >= s->buf_len) {
         /* buffer full, read nothing */
-        return 0;
+        goto read_end;
     }
     realsize = MIN(realsize, s->buf_len - s->buf_off);
     memcpy(s->orig_buf + s->buf_off, ptr, realsize);
@@ -231,15 +252,26 @@ static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
             continue;
 
         if ((s->buf_off >= acb->end)) {
+            size_t request_length = acb->nb_sectors * BDRV_SECTOR_SIZE;
+
             qemu_iovec_from_buf(acb->qiov, 0, s->orig_buf + acb->start,
                                 acb->end - acb->start);
+
+            if (acb->end - acb->start < request_length) {
+                size_t offset = acb->end - acb->start;
+                qemu_iovec_memset(acb->qiov, offset, 0,
+                                  request_length - offset);
+            }
+
             acb->common.cb(acb->common.opaque, 0);
             qemu_aio_unref(acb);
             s->acb[i] = NULL;
         }
     }
 
-    return realsize;
+read_end:
+    /* curl will error out if we do not return this value */
+    return size * nmemb;
 }
 
 static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
@@ -247,6 +279,8 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
 {
     int i;
     size_t end = start + len;
+    size_t clamped_end = MIN(end, s->len);
+    size_t clamped_len = clamped_end - start;
 
     for (i=0; i<CURL_NUM_STATES; i++) {
         CURLState *state = &s->states[i];
@@ -261,12 +295,15 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
         // Does the existing buffer cover our section?
         if ((start >= state->buf_start) &&
             (start <= buf_end) &&
-            (end >= state->buf_start) &&
-            (end <= buf_end))
+            (clamped_end >= state->buf_start) &&
+            (clamped_end <= buf_end))
         {
             char *buf = state->orig_buf + (start - state->buf_start);
 
-            qemu_iovec_from_buf(acb->qiov, 0, buf, len);
+            qemu_iovec_from_buf(acb->qiov, 0, buf, clamped_len);
+            if (clamped_len < len) {
+                qemu_iovec_memset(acb->qiov, clamped_len, 0, len - clamped_len);
+            }
             acb->common.cb(acb->common.opaque, 0);
 
             return FIND_RET_OK;
@@ -276,13 +313,13 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
         if (state->in_use &&
             (start >= state->buf_start) &&
             (start <= buf_fend) &&
-            (end >= state->buf_start) &&
-            (end <= buf_fend))
+            (clamped_end >= state->buf_start) &&
+            (clamped_end <= buf_fend))
         {
             int j;
 
             acb->start = start - state->buf_start;
-            acb->end = acb->start + len;
+            acb->end = acb->start + clamped_len;
 
             for (j=0; j<CURL_NUM_ACB; j++) {
                 if (!state->acb[j]) {
@@ -352,6 +389,7 @@ static void curl_multi_check_completion(BDRVCURLState *s)
 static void curl_multi_do(void *arg)
 {
     CURLState *s = (CURLState *)arg;
+    CURLSocket *socket, *next_socket;
     int running;
     int r;
 
@@ -359,10 +397,13 @@ static void curl_multi_do(void *arg)
         return;
     }
 
-    do {
-        r = curl_multi_socket_action(s->s->multi, s->sock_fd, 0, &running);
-    } while(r == CURLM_CALL_MULTI_PERFORM);
-
+    /* Need to use _SAFE because curl_multi_socket_action() may trigger
+     * curl_sock_cb() which might modify this list */
+    QLIST_FOREACH_SAFE(socket, &s->sockets, next, next_socket) {
+        do {
+            r = curl_multi_socket_action(s->s->multi, socket->fd, 0, &running);
+        } while (r == CURLM_CALL_MULTI_PERFORM);
+    }
 }
 
 static void curl_multi_read(void *arg)
@@ -466,6 +507,7 @@ static CURLState *curl_init_state(BlockDriverState *bs, BDRVCURLState *s)
 #endif
     }
 
+    QLIST_INIT(&state->sockets);
     state->s = s;
 
     return state;
@@ -475,6 +517,14 @@ static void curl_clean_state(CURLState *s)
 {
     if (s->s->multi)
         curl_multi_remove_handle(s->s->multi, s->curl);
+
+    while (!QLIST_EMPTY(&s->sockets)) {
+        CURLSocket *socket = QLIST_FIRST(&s->sockets);
+
+        QLIST_REMOVE(socket, next);
+        g_free(socket);
+    }
+
     s->in_use = 0;
 }
 
@@ -738,12 +788,12 @@ static void curl_readv_bh_cb(void *p)
     CURLAIOCB *acb = p;
     BDRVCURLState *s = acb->common.bs->opaque;
 
-    size_t start = acb->sector_num * SECTOR_SIZE;
+    size_t start = acb->sector_num * BDRV_SECTOR_SIZE;
     size_t end;
 
     // In case we have the requested data already (e.g. read-ahead),
     // we can just call the callback and be done.
-    switch (curl_find_buf(s, start, acb->nb_sectors * SECTOR_SIZE, acb)) {
+    switch (curl_find_buf(s, start, acb->nb_sectors * BDRV_SECTOR_SIZE, acb)) {
         case FIND_RET_OK:
             qemu_aio_unref(acb);
             // fall through
@@ -762,13 +812,13 @@ static void curl_readv_bh_cb(void *p)
     }
 
     acb->start = 0;
-    acb->end = (acb->nb_sectors * SECTOR_SIZE);
+    acb->end = MIN(acb->nb_sectors * BDRV_SECTOR_SIZE, s->len - start);
 
     state->buf_off = 0;
     g_free(state->orig_buf);
     state->buf_start = start;
-    state->buf_len = acb->end + s->readahead_size;
-    end = MIN(start + state->buf_len, s->len) - 1;
+    state->buf_len = MIN(acb->end + s->readahead_size, s->len - start);
+    end = start + state->buf_len - 1;
     state->orig_buf = g_try_malloc(state->buf_len);
     if (state->buf_len && state->orig_buf == NULL) {
         curl_clean_state(state);
@@ -779,8 +829,8 @@ static void curl_readv_bh_cb(void *p)
     state->acb[0] = acb;
 
     snprintf(state->range, 127, "%zd-%zd", start, end);
-    DPRINTF("CURL (AIO): Reading %d at %zd (%s)\n",
-            (acb->nb_sectors * SECTOR_SIZE), start, state->range);
+    DPRINTF("CURL (AIO): Reading %llu at %zd (%s)\n",
+            (acb->nb_sectors * BDRV_SECTOR_SIZE), start, state->range);
     curl_easy_setopt(state->curl, CURLOPT_RANGE, state->range);
 
     curl_multi_add_handle(s->multi, state->curl);
@@ -886,29 +936,12 @@ static BlockDriver bdrv_ftps = {
     .bdrv_attach_aio_context    = curl_attach_aio_context,
 };
 
-static BlockDriver bdrv_tftp = {
-    .format_name                = "tftp",
-    .protocol_name              = "tftp",
-
-    .instance_size              = sizeof(BDRVCURLState),
-    .bdrv_parse_filename        = curl_parse_filename,
-    .bdrv_file_open             = curl_open,
-    .bdrv_close                 = curl_close,
-    .bdrv_getlength             = curl_getlength,
-
-    .bdrv_aio_readv             = curl_aio_readv,
-
-    .bdrv_detach_aio_context    = curl_detach_aio_context,
-    .bdrv_attach_aio_context    = curl_attach_aio_context,
-};
-
 static void curl_block_init(void)
 {
     bdrv_register(&bdrv_http);
     bdrv_register(&bdrv_https);
     bdrv_register(&bdrv_ftp);
     bdrv_register(&bdrv_ftps);
-    bdrv_register(&bdrv_tftp);
 }
 
 block_init(curl_block_init);
diff --git a/block/mirror.c b/block/mirror.c
index b2c1fb855b..301ba9219a 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -615,6 +615,20 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
     return 0;
 }
 
+/* Called when going out of the streaming phase to flush the bulk of the
+ * data to the medium, or just before completing.
+ */
+static int mirror_flush(MirrorBlockJob *s)
+{
+    int ret = blk_flush(s->target);
+    if (ret < 0) {
+        if (mirror_error_action(s, false, -ret) == BLOCK_ERROR_ACTION_REPORT) {
+            s->ret = ret;
+        }
+    }
+    return ret;
+}
+
 static void coroutine_fn mirror_run(void *opaque)
 {
     MirrorBlockJob *s = opaque;
@@ -727,27 +741,23 @@ static void coroutine_fn mirror_run(void *opaque)
         should_complete = false;
         if (s->in_flight == 0 && cnt == 0) {
             trace_mirror_before_flush(s);
-            ret = blk_flush(s->target);
-            if (ret < 0) {
-                if (mirror_error_action(s, false, -ret) ==
-                    BLOCK_ERROR_ACTION_REPORT) {
-                    goto immediate_exit;
+            if (!s->synced) {
+                if (mirror_flush(s) < 0) {
+                    /* Go check s->ret.  */
+                    continue;
                 }
-            } 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);
+                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) {
@@ -765,7 +775,7 @@ static void coroutine_fn mirror_run(void *opaque)
 
             bdrv_drained_begin(bs);
             cnt = bdrv_get_dirty_count(s->dirty_bitmap);
-            if (cnt > 0) {
+            if (cnt > 0 || mirror_flush(s) < 0) {
                 bdrv_drained_end(bs);
                 continue;
             }
@@ -920,6 +930,7 @@ static const BlockJobDriver mirror_job_driver = {
     .instance_size          = sizeof(MirrorBlockJob),
     .job_type               = BLOCK_JOB_TYPE_MIRROR,
     .set_speed              = mirror_set_speed,
+    .start                  = mirror_run,
     .complete               = mirror_complete,
     .pause                  = mirror_pause,
     .attached_aio_context   = mirror_attached_aio_context,
@@ -930,6 +941,7 @@ static const BlockJobDriver commit_active_job_driver = {
     .instance_size          = sizeof(MirrorBlockJob),
     .job_type               = BLOCK_JOB_TYPE_COMMIT,
     .set_speed              = mirror_set_speed,
+    .start                  = mirror_run,
     .complete               = mirror_complete,
     .pause                  = mirror_pause,
     .attached_aio_context   = mirror_attached_aio_context,
@@ -1007,9 +1019,8 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs,
         }
     }
 
-    s->common.co = qemu_coroutine_create(mirror_run, s);
-    trace_mirror_start(bs, s, s->common.co, opaque);
-    qemu_coroutine_enter(s->common.co);
+    trace_mirror_start(bs, s, opaque);
+    block_job_start(&s->common);
 }
 
 void mirror_start(const char *job_id, BlockDriverState *bs,
diff --git a/block/replication.c b/block/replication.c
index d5e2b0f497..729dd12499 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -421,6 +421,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
     int64_t active_length, hidden_length, disk_length;
     AioContext *aio_context;
     Error *local_err = NULL;
+    BlockJob *job;
 
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
@@ -508,17 +509,18 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
         bdrv_op_block_all(top_bs, s->blocker);
         bdrv_op_unblock(top_bs, BLOCK_OP_TYPE_DATAPLANE, s->blocker);
 
-        backup_start(NULL, s->secondary_disk->bs, s->hidden_disk->bs, 0,
-                     MIRROR_SYNC_MODE_NONE, NULL, false,
-                     BLOCKDEV_ON_ERROR_REPORT, BLOCKDEV_ON_ERROR_REPORT,
-                     BLOCK_JOB_INTERNAL, backup_job_completed, bs,
-                     NULL, &local_err);
+        job = backup_job_create(NULL, s->secondary_disk->bs, s->hidden_disk->bs,
+                                0, MIRROR_SYNC_MODE_NONE, NULL, false,
+                                BLOCKDEV_ON_ERROR_REPORT,
+                                BLOCKDEV_ON_ERROR_REPORT, BLOCK_JOB_INTERNAL,
+                                backup_job_completed, bs, NULL, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             backup_job_cleanup(bs);
             aio_context_release(aio_context);
             return;
         }
+        block_job_start(job);
         break;
     default:
         aio_context_release(aio_context);
diff --git a/block/stream.c b/block/stream.c
index b05856bd65..1523ba7dfb 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -218,6 +218,7 @@ static const BlockJobDriver stream_job_driver = {
     .instance_size = sizeof(StreamBlockJob),
     .job_type      = BLOCK_JOB_TYPE_STREAM,
     .set_speed     = stream_set_speed,
+    .start         = stream_run,
 };
 
 void stream_start(const char *job_id, BlockDriverState *bs,
@@ -254,7 +255,6 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     s->bs_flags = orig_bs_flags;
 
     s->on_error = on_error;
-    s->common.co = qemu_coroutine_create(stream_run, s);
-    trace_stream_start(bs, base, s, s->common.co);
-    qemu_coroutine_enter(s->common.co);
+    trace_stream_start(bs, base, s);
+    block_job_start(&s->common);
 }
diff --git a/block/trace-events b/block/trace-events
index 882c9034c2..cfc05f2478 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -19,14 +19,14 @@ bdrv_co_do_copy_on_readv(void *bs, int64_t offset, unsigned int bytes, int64_t c
 
 # block/stream.c
 stream_one_iteration(void *s, int64_t sector_num, int nb_sectors, int is_allocated) "s %p sector_num %"PRId64" nb_sectors %d is_allocated %d"
-stream_start(void *bs, void *base, void *s, void *co) "bs %p base %p s %p co %p"
+stream_start(void *bs, void *base, void *s) "bs %p base %p s %p"
 
 # block/commit.c
 commit_one_iteration(void *s, int64_t sector_num, int nb_sectors, int is_allocated) "s %p sector_num %"PRId64" nb_sectors %d is_allocated %d"
-commit_start(void *bs, void *base, void *top, void *s, void *co) "bs %p base %p top %p s %p co %p"
+commit_start(void *bs, void *base, void *top, void *s) "bs %p base %p top %p s %p"
 
 # block/mirror.c
-mirror_start(void *bs, void *s, void *co, void *opaque) "bs %p s %p co %p opaque %p"
+mirror_start(void *bs, void *s, void *opaque) "bs %p s %p opaque %p"
 mirror_restart_iter(void *s, int64_t cnt) "s %p dirty count %"PRId64
 mirror_before_flush(void *s) "s %p"
 mirror_before_drain(void *s, int64_t cnt) "s %p dirty count %"PRId64
diff --git a/blockdev.c b/blockdev.c
index 102ca9fe01..245e1e1d17 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1811,7 +1811,7 @@ typedef struct DriveBackupState {
     BlockJob *job;
 } DriveBackupState;
 
-static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn,
+static BlockJob *do_drive_backup(DriveBackup *backup, BlockJobTxn *txn,
                             Error **errp);
 
 static void drive_backup_prepare(BlkActionState *common, Error **errp)
@@ -1835,23 +1835,26 @@ static void drive_backup_prepare(BlkActionState *common, Error **errp)
     bdrv_drained_begin(bs);
     state->bs = bs;
 
-    do_drive_backup(backup, common->block_job_txn, &local_err);
+    state->job = do_drive_backup(backup, common->block_job_txn, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         return;
     }
+}
 
-    state->job = state->bs->job;
+static void drive_backup_commit(BlkActionState *common)
+{
+    DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
+    assert(state->job);
+    block_job_start(state->job);
 }
 
 static void drive_backup_abort(BlkActionState *common)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
-    BlockDriverState *bs = state->bs;
 
-    /* Only cancel if it's the job we started */
-    if (bs && bs->job && bs->job == state->job) {
-        block_job_cancel_sync(bs->job);
+    if (state->job) {
+        block_job_cancel_sync(state->job);
     }
 }
 
@@ -1872,8 +1875,8 @@ typedef struct BlockdevBackupState {
     AioContext *aio_context;
 } BlockdevBackupState;
 
-static void do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn,
-                               Error **errp);
+static BlockJob *do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn,
+                                    Error **errp);
 
 static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
 {
@@ -1906,23 +1909,26 @@ static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
     state->bs = bs;
     bdrv_drained_begin(state->bs);
 
-    do_blockdev_backup(backup, common->block_job_txn, &local_err);
+    state->job = do_blockdev_backup(backup, common->block_job_txn, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         return;
     }
+}
 
-    state->job = state->bs->job;
+static void blockdev_backup_commit(BlkActionState *common)
+{
+    BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
+    assert(state->job);
+    block_job_start(state->job);
 }
 
 static void blockdev_backup_abort(BlkActionState *common)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
-    BlockDriverState *bs = state->bs;
 
-    /* Only cancel if it's the job we started */
-    if (bs && bs->job && bs->job == state->job) {
-        block_job_cancel_sync(bs->job);
+    if (state->job) {
+        block_job_cancel_sync(state->job);
     }
 }
 
@@ -2072,12 +2078,14 @@ static const BlkActionOps actions[] = {
     [TRANSACTION_ACTION_KIND_DRIVE_BACKUP] = {
         .instance_size = sizeof(DriveBackupState),
         .prepare = drive_backup_prepare,
+        .commit = drive_backup_commit,
         .abort = drive_backup_abort,
         .clean = drive_backup_clean,
     },
     [TRANSACTION_ACTION_KIND_BLOCKDEV_BACKUP] = {
         .instance_size = sizeof(BlockdevBackupState),
         .prepare = blockdev_backup_prepare,
+        .commit = blockdev_backup_commit,
         .abort = blockdev_backup_abort,
         .clean = blockdev_backup_clean,
     },
@@ -3106,11 +3114,13 @@ out:
     aio_context_release(aio_context);
 }
 
-static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn, Error **errp)
+static BlockJob *do_drive_backup(DriveBackup *backup, BlockJobTxn *txn,
+                                 Error **errp)
 {
     BlockDriverState *bs;
     BlockDriverState *target_bs;
     BlockDriverState *source = NULL;
+    BlockJob *job = NULL;
     BdrvDirtyBitmap *bmap = NULL;
     AioContext *aio_context;
     QDict *options = NULL;
@@ -3139,7 +3149,7 @@ static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn, Error **errp)
 
     bs = qmp_get_root_bs(backup->device, errp);
     if (!bs) {
-        return;
+        return NULL;
     }
 
     aio_context = bdrv_get_aio_context(bs);
@@ -3213,10 +3223,10 @@ static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn, Error **errp)
         }
     }
 
-    backup_start(backup->job_id, bs, target_bs, backup->speed, backup->sync,
-                 bmap, backup->compress, backup->on_source_error,
-                 backup->on_target_error, BLOCK_JOB_DEFAULT,
-                 NULL, NULL, txn, &local_err);
+    job = backup_job_create(backup->job_id, bs, target_bs, backup->speed,
+                            backup->sync, bmap, backup->compress,
+                            backup->on_source_error, backup->on_target_error,
+                            BLOCK_JOB_DEFAULT, NULL, NULL, txn, &local_err);
     bdrv_unref(target_bs);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
@@ -3225,11 +3235,17 @@ static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn, Error **errp)
 
 out:
     aio_context_release(aio_context);
+    return job;
 }
 
 void qmp_drive_backup(DriveBackup *arg, Error **errp)
 {
-    return do_drive_backup(arg, NULL, errp);
+
+    BlockJob *job;
+    job = do_drive_backup(arg, NULL, errp);
+    if (job) {
+        block_job_start(job);
+    }
 }
 
 BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
@@ -3237,12 +3253,14 @@ BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
     return bdrv_named_nodes_list(errp);
 }
 
-void do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn, Error **errp)
+BlockJob *do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn,
+                             Error **errp)
 {
     BlockDriverState *bs;
     BlockDriverState *target_bs;
     Error *local_err = NULL;
     AioContext *aio_context;
+    BlockJob *job = NULL;
 
     if (!backup->has_speed) {
         backup->speed = 0;
@@ -3262,7 +3280,7 @@ void do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn, Error **errp)
 
     bs = qmp_get_root_bs(backup->device, errp);
     if (!bs) {
-        return;
+        return NULL;
     }
 
     aio_context = bdrv_get_aio_context(bs);
@@ -3284,20 +3302,25 @@ void do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn, Error **errp)
             goto out;
         }
     }
-    backup_start(backup->job_id, bs, target_bs, backup->speed, backup->sync,
-                 NULL, backup->compress, backup->on_source_error,
-                 backup->on_target_error, BLOCK_JOB_DEFAULT,
-                 NULL, NULL, txn, &local_err);
+    job = backup_job_create(backup->job_id, bs, target_bs, backup->speed,
+                            backup->sync, NULL, backup->compress,
+                            backup->on_source_error, backup->on_target_error,
+                            BLOCK_JOB_DEFAULT, NULL, NULL, txn, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
     }
 out:
     aio_context_release(aio_context);
+    return job;
 }
 
 void qmp_blockdev_backup(BlockdevBackup *arg, Error **errp)
 {
-    do_blockdev_backup(arg, NULL, errp);
+    BlockJob *job;
+    job = do_blockdev_backup(arg, NULL, errp);
+    if (job) {
+        block_job_start(job);
+    }
 }
 
 /* Parameter check and block job starting for drive mirroring.
diff --git a/blockjob.c b/blockjob.c
index 4aa14a4974..513620c199 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -174,7 +174,9 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
     job->blk           = blk;
     job->cb            = cb;
     job->opaque        = opaque;
-    job->busy          = true;
+    job->busy          = false;
+    job->paused        = true;
+    job->pause_count   = 1;
     job->refcnt        = 1;
     bs->job = job;
 
@@ -202,6 +204,23 @@ bool block_job_is_internal(BlockJob *job)
     return (job->id == NULL);
 }
 
+static bool block_job_started(BlockJob *job)
+{
+    return job->co;
+}
+
+void block_job_start(BlockJob *job)
+{
+    assert(job && !block_job_started(job) && job->paused &&
+           !job->busy && job->driver->start);
+    job->co = qemu_coroutine_create(job->driver->start, job);
+    if (--job->pause_count == 0) {
+        job->paused = false;
+        job->busy = true;
+        qemu_coroutine_enter(job->co);
+    }
+}
+
 void block_job_ref(BlockJob *job)
 {
     ++job->refcnt;
@@ -241,21 +260,29 @@ static void block_job_completed_single(BlockJob *job)
             job->driver->abort(job);
         }
     }
+    if (job->driver->clean) {
+        job->driver->clean(job);
+    }
 
     if (job->cb) {
         job->cb(job->opaque, job->ret);
     }
-    if (block_job_is_cancelled(job)) {
-        block_job_event_cancelled(job);
-    } else {
-        const char *msg = NULL;
-        if (job->ret < 0) {
-            msg = strerror(-job->ret);
+
+    /* Emit events only if we actually started */
+    if (block_job_started(job)) {
+        if (block_job_is_cancelled(job)) {
+            block_job_event_cancelled(job);
+        } else {
+            const char *msg = NULL;
+            if (job->ret < 0) {
+                msg = strerror(-job->ret);
+            }
+            block_job_event_completed(job, msg);
         }
-        block_job_event_completed(job, msg);
     }
 
     if (job->txn) {
+        QLIST_REMOVE(job, txn_list);
         block_job_txn_unref(job->txn);
     }
     block_job_unref(job);
@@ -359,7 +386,8 @@ void block_job_complete(BlockJob *job, Error **errp)
 {
     /* Should not be reachable via external interface for internal jobs */
     assert(job->id);
-    if (job->pause_count || job->cancelled || !job->driver->complete) {
+    if (job->pause_count || job->cancelled ||
+        !block_job_started(job) || !job->driver->complete) {
         error_setg(errp, "The active block job '%s' cannot be completed",
                    job->id);
         return;
@@ -391,6 +419,8 @@ bool block_job_user_paused(BlockJob *job)
 
 void coroutine_fn block_job_pause_point(BlockJob *job)
 {
+    assert(job && block_job_started(job));
+
     if (!block_job_should_pause(job)) {
         return;
     }
@@ -442,9 +472,13 @@ void block_job_enter(BlockJob *job)
 
 void block_job_cancel(BlockJob *job)
 {
-    job->cancelled = true;
-    block_job_iostatus_reset(job);
-    block_job_enter(job);
+    if (block_job_started(job)) {
+        job->cancelled = true;
+        block_job_iostatus_reset(job);
+        block_job_enter(job);
+    } else {
+        block_job_completed(job, -ECANCELED);
+    }
 }
 
 bool block_job_is_cancelled(BlockJob *job)
diff --git a/docs/qmp-commands.txt b/docs/qmp-commands.txt
index 6afa87298d..abf210a596 100644
--- a/docs/qmp-commands.txt
+++ b/docs/qmp-commands.txt
@@ -1803,7 +1803,7 @@ Each json-object contain the following:
                                 "file", "file", "ftp", "ftps", "host_cdrom",
                                 "host_device", "http", "https",
                                 "nbd", "parallels", "qcow", "qcow2", "raw",
-                                "tftp", "vdi", "vmdk", "vpc", "vvfat"
+                                "vdi", "vmdk", "vpc", "vvfat"
          - "backing_file": backing file name (json-string, optional)
          - "backing_file_depth": number of files in the backing file chain (json-int)
          - "encrypted": true if encrypted, false otherwise (json-bool)
diff --git a/include/block/block_int.h b/include/block/block_int.h
index b02abbd618..83a423c580 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -748,7 +748,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
                   bool unmap, Error **errp);
 
 /*
- * backup_start:
+ * backup_job_create:
  * @job_id: The id of the newly-created job, or %NULL to use the
  * device name of @bs.
  * @bs: Block device to operate on.
@@ -764,18 +764,19 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
  * @opaque: Opaque pointer value passed to @cb.
  * @txn: Transaction that this job is part of (may be NULL).
  *
- * Start a backup operation on @bs.  Clusters in @bs are written to @target
+ * Create a backup operation on @bs.  Clusters in @bs are written to @target
  * until the job is cancelled or manually completed.
  */
-void backup_start(const char *job_id, BlockDriverState *bs,
-                  BlockDriverState *target, int64_t speed,
-                  MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
-                  bool compress,
-                  BlockdevOnError on_source_error,
-                  BlockdevOnError on_target_error,
-                  int creation_flags,
-                  BlockCompletionFunc *cb, void *opaque,
-                  BlockJobTxn *txn, Error **errp);
+BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
+                            BlockDriverState *target, int64_t speed,
+                            MirrorSyncMode sync_mode,
+                            BdrvDirtyBitmap *sync_bitmap,
+                            bool compress,
+                            BlockdevOnError on_source_error,
+                            BlockdevOnError on_target_error,
+                            int creation_flags,
+                            BlockCompletionFunc *cb, void *opaque,
+                            BlockJobTxn *txn, Error **errp);
 
 void hmp_drive_add_node(Monitor *mon, const char *optstr);
 
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 356cacf004..1acb256223 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -189,6 +189,15 @@ void block_job_add_bdrv(BlockJob *job, BlockDriverState *bs);
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp);
 
 /**
+ * block_job_start:
+ * @job: A job that has not yet been started.
+ *
+ * Begins execution of a block job.
+ * Takes ownership of one reference to the job object.
+ */
+void block_job_start(BlockJob *job);
+
+/**
  * block_job_cancel:
  * @job: The job to be canceled.
  *
diff --git a/include/block/blockjob_int.h b/include/block/blockjob_int.h
index 40275e4437..82238229c6 100644
--- a/include/block/blockjob_int.h
+++ b/include/block/blockjob_int.h
@@ -47,6 +47,9 @@ struct BlockJobDriver {
     /** Optional callback for job types that need to forward I/O status reset */
     void (*iostatus_reset)(BlockJob *job);
 
+    /** Mandatory: Entrypoint for the Coroutine. */
+    CoroutineEntry *start;
+
     /**
      * Optional callback for job types whose completion must be triggered
      * manually.
@@ -74,6 +77,14 @@ struct BlockJobDriver {
     void (*abort)(BlockJob *job);
 
     /**
+     * If the callback is not NULL, it will be invoked after a call to either
+     * .commit() or .abort(). Regardless of which callback is invoked after
+     * completion, .clean() will always be called, even if the job does not
+     * belong to a transaction group.
+     */
+    void (*clean)(BlockJob *job);
+
+    /**
      * If the callback is not NULL, it will be invoked when the job transitions
      * into the paused state.  Paused jobs must not perform any asynchronous
      * I/O or event loop activity.  This callback is used to quiesce jobs.
diff --git a/qapi/block-core.json b/qapi/block-core.json
index bcd3b9effe..c29bef7ee1 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -243,12 +243,12 @@
 #       0.14.0 this can be: 'blkdebug', 'bochs', 'cloop', 'cow', 'dmg',
 #       'file', 'file', 'ftp', 'ftps', 'host_cdrom', 'host_device',
 #       'http', 'https', 'luks', 'nbd', 'parallels', 'qcow',
-#       'qcow2', 'raw', 'tftp', 'vdi', 'vmdk', 'vpc', 'vvfat'
+#       'qcow2', 'raw', 'vdi', 'vmdk', 'vpc', 'vvfat'
 #       2.2: 'archipelago' added, 'cow' dropped
 #       2.3: 'host_floppy' deprecated
 #       2.5: 'host_floppy' dropped
 #       2.6: 'luks' added
-#       2.8: 'replication' added
+#       2.8: 'replication' added, 'tftp' dropped
 #
 # @backing_file: #optional the name of the backing file (for copy-on-write)
 #
@@ -1723,7 +1723,7 @@
             'dmg', 'file', 'ftp', 'ftps', 'gluster', 'host_cdrom',
             'host_device', 'http', 'https', 'luks', 'nbd', 'nfs', 'null-aio',
             'null-co', 'parallels', 'qcow', 'qcow2', 'qed', 'quorum', 'raw',
-            'replication', 'ssh', 'tftp', 'vdi', 'vhdx', 'vmdk', 'vpc',
+            'replication', 'ssh', 'vdi', 'vhdx', 'vmdk', 'vpc',
             'vvfat' ] }
 
 ##
@@ -2410,7 +2410,6 @@
       'replication':'BlockdevOptionsReplication',
 # TODO sheepdog: Wait for structured options
       'ssh':        'BlockdevOptionsSsh',
-      'tftp':       'BlockdevOptionsCurl',
       'vdi':        'BlockdevOptionsGenericFormat',
       'vhdx':       'BlockdevOptionsGenericFormat',
       'vmdk':       'BlockdevOptionsGenericCOWFormat',
diff --git a/qemu-options.hx b/qemu-options.hx
index 4536e18ac0..4a5b29f349 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2606,8 +2606,8 @@ qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img
 
 See also @url{http://www.gluster.org}.
 
-@item HTTP/HTTPS/FTP/FTPS/TFTP
-QEMU supports read-only access to files accessed over http(s), ftp(s) and tftp.
+@item HTTP/HTTPS/FTP/FTPS
+QEMU supports read-only access to files accessed over http(s) and ftp(s).
 
 Syntax using a single filename:
 @example
@@ -2617,7 +2617,7 @@ Syntax using a single filename:
 where:
 @table @option
 @item protocol
-'http', 'https', 'ftp', 'ftps', or 'tftp'.
+'http', 'https', 'ftp', or 'ftps'.
 
 @item username
 Optional username for authentication to the remote server.
diff --git a/tests/qemu-iotests/109 b/tests/qemu-iotests/109
index 280ed27aa9..927151a285 100755
--- a/tests/qemu-iotests/109
+++ b/tests/qemu-iotests/109
@@ -62,6 +62,9 @@ function run_qemu()
         "return"
 
     _send_qemu_cmd $QEMU_HANDLE '' "$qmp_event"
+    if test "$qmp_event" = BLOCK_JOB_ERROR; then
+        _send_qemu_cmd $QEMU_HANDLE '' "BLOCK_JOB_COMPLETED"
+    fi
     _send_qemu_cmd $QEMU_HANDLE '{"execute":"query-block-jobs"}' "return"
     _cleanup_qemu
 }
diff --git a/tests/qemu-iotests/124 b/tests/qemu-iotests/124
index f06938eeb7..d0d2c2bfb0 100644
--- a/tests/qemu-iotests/124
+++ b/tests/qemu-iotests/124
@@ -395,19 +395,7 @@ class TestIncrementalBackup(TestIncrementalBackupBase):
         self.check_backups()
 
 
-    def test_transaction_failure(self):
-        '''Test: Verify backups made from a transaction that partially fails.
-
-        Add a second drive with its own unique pattern, and add a bitmap to each
-        drive. Use blkdebug to interfere with the backup on just one drive and
-        attempt to create a coherent incremental backup across both drives.
-
-        verify a failure in one but not both, then delete the failed stubs and
-        re-run the same transaction.
-
-        verify that both incrementals are created successfully.
-        '''
-
+    def do_transaction_failure_test(self, race=False):
         # Create a second drive, with pattern:
         drive1 = self.add_node('drive1')
         self.img_create(drive1['file'], drive1['fmt'])
@@ -451,9 +439,10 @@ class TestIncrementalBackup(TestIncrementalBackupBase):
         self.assertFalse(self.vm.get_qmp_events(wait=False))
 
         # Emulate some writes
-        self.hmp_io_writes(drive0['id'], (('0xab', 0, 512),
-                                          ('0xfe', '16M', '256k'),
-                                          ('0x64', '32736k', '64k')))
+        if not race:
+            self.hmp_io_writes(drive0['id'], (('0xab', 0, 512),
+                                              ('0xfe', '16M', '256k'),
+                                              ('0x64', '32736k', '64k')))
         self.hmp_io_writes(drive1['id'], (('0xba', 0, 512),
                                           ('0xef', '16M', '256k'),
                                           ('0x46', '32736k', '64k')))
@@ -463,7 +452,8 @@ class TestIncrementalBackup(TestIncrementalBackupBase):
         target1 = self.prepare_backup(dr1bm0)
 
         # Ask for a new incremental backup per-each drive,
-        # expecting drive1's backup to fail:
+        # expecting drive1's backup to fail. In the 'race' test,
+        # we expect drive1 to attempt to cancel the empty drive0 job.
         transaction = [
             transaction_drive_backup(drive0['id'], target0, sync='incremental',
                                      format=drive0['fmt'], mode='existing',
@@ -488,9 +478,15 @@ class TestIncrementalBackup(TestIncrementalBackupBase):
         self.assert_no_active_block_jobs()
 
         # Delete drive0's successful target and eliminate our record of the
-        # unsuccessful drive1 target. Then re-run the same transaction.
+        # unsuccessful drive1 target.
         dr0bm0.del_target()
         dr1bm0.del_target()
+        if race:
+            # Don't re-run the transaction, we only wanted to test the race.
+            self.vm.shutdown()
+            return
+
+        # Re-run the same transaction:
         target0 = self.prepare_backup(dr0bm0)
         target1 = self.prepare_backup(dr1bm0)
 
@@ -511,6 +507,27 @@ class TestIncrementalBackup(TestIncrementalBackupBase):
         self.vm.shutdown()
         self.check_backups()
 
+    def test_transaction_failure(self):
+        '''Test: Verify backups made from a transaction that partially fails.
+
+        Add a second drive with its own unique pattern, and add a bitmap to each
+        drive. Use blkdebug to interfere with the backup on just one drive and
+        attempt to create a coherent incremental backup across both drives.
+
+        verify a failure in one but not both, then delete the failed stubs and
+        re-run the same transaction.
+
+        verify that both incrementals are created successfully.
+        '''
+        self.do_transaction_failure_test()
+
+    def test_transaction_failure_race(self):
+        '''Test: Verify that transactions with jobs that have no data to
+        transfer do not cause race conditions in the cancellation of the entire
+        transaction job group.
+        '''
+        self.do_transaction_failure_test(race=True)
+
 
     def test_sync_dirty_bitmap_missing(self):
         self.assert_no_active_block_jobs()
diff --git a/tests/qemu-iotests/124.out b/tests/qemu-iotests/124.out
index 36376bed87..e56cae021b 100644
--- a/tests/qemu-iotests/124.out
+++ b/tests/qemu-iotests/124.out
@@ -1,5 +1,5 @@
-..........
+...........
 ----------------------------------------------------------------------
-Ran 10 tests
+Ran 11 tests
 
 OK
diff --git a/tests/test-blockjob-txn.c b/tests/test-blockjob-txn.c
index f9afc3be41..b132e39097 100644
--- a/tests/test-blockjob-txn.c
+++ b/tests/test-blockjob-txn.c
@@ -24,10 +24,6 @@ typedef struct {
     int *result;
 } TestBlockJob;
 
-static const BlockJobDriver test_block_job_driver = {
-    .instance_size = sizeof(TestBlockJob),
-};
-
 static void test_block_job_complete(BlockJob *job, void *opaque)
 {
     BlockDriverState *bs = blk_bs(job->blk);
@@ -77,6 +73,11 @@ static void test_block_job_cb(void *opaque, int ret)
     g_free(data);
 }
 
+static const BlockJobDriver test_block_job_driver = {
+    .instance_size = sizeof(TestBlockJob),
+    .start = test_block_job_run,
+};
+
 /* Create a block job that completes with a given return code after a given
  * number of event loop iterations.  The return code is stored in the given
  * result pointer.
@@ -104,10 +105,9 @@ static BlockJob *test_block_job_start(unsigned int iterations,
     s->use_timer = use_timer;
     s->rc = rc;
     s->result = result;
-    s->common.co = qemu_coroutine_create(test_block_job_run, s);
     data->job = s;
     data->result = result;
-    qemu_coroutine_enter(s->common.co);
+    block_job_start(&s->common);
     return &s->common;
 }