Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches

- mirror: Fix active mirror deadlock
- replication: Fix crashes due to operations on wrong BdrvChild
- configure: Add option to use driver whitelist even in tools
- vvfat: Fix crash when opening image read-write
- export: Fix crash in error path with fixed-iothread=false

# gpg: Signature made Tue 20 Jul 2021 16:09:23 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  iotests/307: Test iothread conflict for exports
  block/export: Conditionally ignore set-context error
  block/vvfat: fix: drop backing
  replication: Remove workaround
  replication: Properly attach children
  replication: Reduce usage of s->hidden_disk and s->secondary_disk
  replication: Remove s->active_disk
  block: Add option to use driver whitelist even in tools
  block/mirror: fix active mirror dead-lock in mirror_wait_on_conflicts
  iotest 151: add test-case that shows active mirror dead-lock
  block/mirror: set .co for active-write MirrorOp objects

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

11 files changed, 182 insertions, 89 deletions

diff --git a/block.c b/block.c
index be083f389e..e97ce0b1c8 100644
--- a/block.c
+++ b/block.c
@@ -6162,6 +6162,9 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
 
 void bdrv_init(void)
 {
+#ifdef CONFIG_BDRV_WHITELIST_TOOLS
+    use_bdrv_whitelist = 1;
+#endif
     module_call_init(MODULE_INIT_BLOCK);
 }
 
diff --git a/block/export/export.c b/block/export/export.c
index fec7d9f738..6d3b9964c8 100644
--- a/block/export/export.c
+++ b/block/export/export.c
@@ -111,6 +111,7 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
     if (export->has_iothread) {
         IOThread *iothread;
         AioContext *new_ctx;
+        Error **set_context_errp;
 
         iothread = iothread_by_id(export->iothread);
         if (!iothread) {
@@ -120,7 +121,9 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
 
         new_ctx = iothread_get_aio_context(iothread);
 
-        ret = bdrv_try_set_aio_context(bs, new_ctx, errp);
+        /* Ignore errors with fixed-iothread=false */
+        set_context_errp = fixed_iothread ? errp : NULL;
+        ret = bdrv_try_set_aio_context(bs, new_ctx, set_context_errp);
         if (ret == 0) {
             aio_context_release(ctx);
             aio_context_acquire(new_ctx);
diff --git a/block/mirror.c b/block/mirror.c
index 019f6deaa5..98fc66eabf 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -107,6 +107,7 @@ struct MirrorOp {
     bool is_in_flight;
     CoQueue waiting_requests;
     Coroutine *co;
+    MirrorOp *waiting_for_op;
 
     QTAILQ_ENTRY(MirrorOp) next;
 };
@@ -159,7 +160,18 @@ static void coroutine_fn mirror_wait_on_conflicts(MirrorOp *self,
             if (ranges_overlap(self_start_chunk, self_nb_chunks,
                                op_start_chunk, op_nb_chunks))
             {
+                /*
+                 * If the operation is already (indirectly) waiting for us, or
+                 * will wait for us as soon as it wakes up, then just go on
+                 * (instead of producing a deadlock in the former case).
+                 */
+                if (op->waiting_for_op) {
+                    continue;
+                }
+
+                self->waiting_for_op = op;
                 qemu_co_queue_wait(&op->waiting_requests, NULL);
+                self->waiting_for_op = NULL;
                 break;
             }
         }
@@ -1343,6 +1355,7 @@ static MirrorOp *coroutine_fn active_write_prepare(MirrorBlockJob *s,
         .bytes              = bytes,
         .is_active_write    = true,
         .is_in_flight       = true,
+        .co                 = qemu_coroutine_self(),
     };
     qemu_co_queue_init(&op->waiting_requests);
     QTAILQ_INSERT_TAIL(&s->ops_in_flight, op, next);
diff --git a/block/replication.c b/block/replication.c
index 774e15df16..32444b9a8f 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -35,7 +35,6 @@ typedef enum {
 typedef struct BDRVReplicationState {
     ReplicationMode mode;
     ReplicationStage stage;
-    BdrvChild *active_disk;
     BlockJob *commit_job;
     BdrvChild *hidden_disk;
     BdrvChild *secondary_disk;
@@ -166,7 +165,12 @@ static void replication_child_perm(BlockDriverState *bs, BdrvChild *c,
                                    uint64_t perm, uint64_t shared,
                                    uint64_t *nperm, uint64_t *nshared)
 {
-    *nperm = BLK_PERM_CONSISTENT_READ;
+    if (role & BDRV_CHILD_PRIMARY) {
+        *nperm = BLK_PERM_CONSISTENT_READ;
+    } else {
+        *nperm = 0;
+    }
+
     if ((bs->open_flags & (BDRV_O_INACTIVE | BDRV_O_RDWR)) == BDRV_O_RDWR) {
         *nperm |= BLK_PERM_WRITE;
     }
@@ -307,8 +311,10 @@ out:
     return ret;
 }
 
-static void secondary_do_checkpoint(BDRVReplicationState *s, Error **errp)
+static void secondary_do_checkpoint(BlockDriverState *bs, Error **errp)
 {
+    BDRVReplicationState *s = bs->opaque;
+    BdrvChild *active_disk = bs->file;
     Error *local_err = NULL;
     int ret;
 
@@ -323,13 +329,13 @@ static void secondary_do_checkpoint(BDRVReplicationState *s, Error **errp)
         return;
     }
 
-    if (!s->active_disk->bs->drv) {
+    if (!active_disk->bs->drv) {
         error_setg(errp, "Active disk %s is ejected",
-                   s->active_disk->bs->node_name);
+                   active_disk->bs->node_name);
         return;
     }
 
-    ret = bdrv_make_empty(s->active_disk, errp);
+    ret = bdrv_make_empty(active_disk, errp);
     if (ret < 0) {
         return;
     }
@@ -340,17 +346,7 @@ static void secondary_do_checkpoint(BDRVReplicationState *s, Error **errp)
         return;
     }
 
-    BlockBackend *blk = blk_new(qemu_get_current_aio_context(),
-                                BLK_PERM_WRITE, BLK_PERM_ALL);
-    blk_insert_bs(blk, s->hidden_disk->bs, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        blk_unref(blk);
-        return;
-    }
-
-    ret = blk_make_empty(blk, errp);
-    blk_unref(blk);
+    ret = bdrv_make_empty(s->hidden_disk, errp);
     if (ret < 0) {
         return;
     }
@@ -365,27 +361,35 @@ static void reopen_backing_file(BlockDriverState *bs, bool writable,
                                 Error **errp)
 {
     BDRVReplicationState *s = bs->opaque;
+    BdrvChild *hidden_disk, *secondary_disk;
     BlockReopenQueue *reopen_queue = NULL;
 
+    /*
+     * s->hidden_disk and s->secondary_disk may not be set yet, as they will
+     * only be set after the children are writable.
+     */
+    hidden_disk = bs->file->bs->backing;
+    secondary_disk = hidden_disk->bs->backing;
+
     if (writable) {
-        s->orig_hidden_read_only = bdrv_is_read_only(s->hidden_disk->bs);
-        s->orig_secondary_read_only = bdrv_is_read_only(s->secondary_disk->bs);
+        s->orig_hidden_read_only = bdrv_is_read_only(hidden_disk->bs);
+        s->orig_secondary_read_only = bdrv_is_read_only(secondary_disk->bs);
     }
 
-    bdrv_subtree_drained_begin(s->hidden_disk->bs);
-    bdrv_subtree_drained_begin(s->secondary_disk->bs);
+    bdrv_subtree_drained_begin(hidden_disk->bs);
+    bdrv_subtree_drained_begin(secondary_disk->bs);
 
     if (s->orig_hidden_read_only) {
         QDict *opts = qdict_new();
         qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
-        reopen_queue = bdrv_reopen_queue(reopen_queue, s->hidden_disk->bs,
+        reopen_queue = bdrv_reopen_queue(reopen_queue, hidden_disk->bs,
                                          opts, true);
     }
 
     if (s->orig_secondary_read_only) {
         QDict *opts = qdict_new();
         qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
-        reopen_queue = bdrv_reopen_queue(reopen_queue, s->secondary_disk->bs,
+        reopen_queue = bdrv_reopen_queue(reopen_queue, secondary_disk->bs,
                                          opts, true);
     }
 
@@ -400,8 +404,8 @@ static void reopen_backing_file(BlockDriverState *bs, bool writable,
         }
     }
 
-    bdrv_subtree_drained_end(s->hidden_disk->bs);
-    bdrv_subtree_drained_end(s->secondary_disk->bs);
+    bdrv_subtree_drained_end(hidden_disk->bs);
+    bdrv_subtree_drained_end(secondary_disk->bs);
 }
 
 static void backup_job_cleanup(BlockDriverState *bs)
@@ -458,6 +462,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
     BlockDriverState *bs = rs->opaque;
     BDRVReplicationState *s;
     BlockDriverState *top_bs;
+    BdrvChild *active_disk, *hidden_disk, *secondary_disk;
     int64_t active_length, hidden_length, disk_length;
     AioContext *aio_context;
     Error *local_err = NULL;
@@ -495,32 +500,31 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
     case REPLICATION_MODE_PRIMARY:
         break;
     case REPLICATION_MODE_SECONDARY:
-        s->active_disk = bs->file;
-        if (!s->active_disk || !s->active_disk->bs ||
-                                    !s->active_disk->bs->backing) {
+        active_disk = bs->file;
+        if (!active_disk || !active_disk->bs || !active_disk->bs->backing) {
             error_setg(errp, "Active disk doesn't have backing file");
             aio_context_release(aio_context);
             return;
         }
 
-        s->hidden_disk = s->active_disk->bs->backing;
-        if (!s->hidden_disk->bs || !s->hidden_disk->bs->backing) {
+        hidden_disk = active_disk->bs->backing;
+        if (!hidden_disk->bs || !hidden_disk->bs->backing) {
             error_setg(errp, "Hidden disk doesn't have backing file");
             aio_context_release(aio_context);
             return;
         }
 
-        s->secondary_disk = s->hidden_disk->bs->backing;
-        if (!s->secondary_disk->bs || !bdrv_has_blk(s->secondary_disk->bs)) {
+        secondary_disk = hidden_disk->bs->backing;
+        if (!secondary_disk->bs || !bdrv_has_blk(secondary_disk->bs)) {
             error_setg(errp, "The secondary disk doesn't have block backend");
             aio_context_release(aio_context);
             return;
         }
 
         /* verify the length */
-        active_length = bdrv_getlength(s->active_disk->bs);
-        hidden_length = bdrv_getlength(s->hidden_disk->bs);
-        disk_length = bdrv_getlength(s->secondary_disk->bs);
+        active_length = bdrv_getlength(active_disk->bs);
+        hidden_length = bdrv_getlength(hidden_disk->bs);
+        disk_length = bdrv_getlength(secondary_disk->bs);
         if (active_length < 0 || hidden_length < 0 || disk_length < 0 ||
             active_length != hidden_length || hidden_length != disk_length) {
             error_setg(errp, "Active disk, hidden disk, secondary disk's length"
@@ -530,10 +534,10 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
         }
 
         /* Must be true, or the bdrv_getlength() calls would have failed */
-        assert(s->active_disk->bs->drv && s->hidden_disk->bs->drv);
+        assert(active_disk->bs->drv && hidden_disk->bs->drv);
 
-        if (!s->active_disk->bs->drv->bdrv_make_empty ||
-            !s->hidden_disk->bs->drv->bdrv_make_empty) {
+        if (!active_disk->bs->drv->bdrv_make_empty ||
+            !hidden_disk->bs->drv->bdrv_make_empty) {
             error_setg(errp,
                        "Active disk or hidden disk doesn't support make_empty");
             aio_context_release(aio_context);
@@ -548,6 +552,26 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
             return;
         }
 
+        bdrv_ref(hidden_disk->bs);
+        s->hidden_disk = bdrv_attach_child(bs, hidden_disk->bs, "hidden disk",
+                                           &child_of_bds, BDRV_CHILD_DATA,
+                                           &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            aio_context_release(aio_context);
+            return;
+        }
+
+        bdrv_ref(secondary_disk->bs);
+        s->secondary_disk = bdrv_attach_child(bs, secondary_disk->bs,
+                                              "secondary disk", &child_of_bds,
+                                              BDRV_CHILD_DATA, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            aio_context_release(aio_context);
+            return;
+        }
+
         /* start backup job now */
         error_setg(&s->blocker,
                    "Block device is in use by internal backup job");
@@ -586,7 +610,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
     s->stage = BLOCK_REPLICATION_RUNNING;
 
     if (s->mode == REPLICATION_MODE_SECONDARY) {
-        secondary_do_checkpoint(s, errp);
+        secondary_do_checkpoint(bs, errp);
     }
 
     s->error = 0;
@@ -615,7 +639,7 @@ static void replication_do_checkpoint(ReplicationState *rs, Error **errp)
     }
 
     if (s->mode == REPLICATION_MODE_SECONDARY) {
-        secondary_do_checkpoint(s, errp);
+        secondary_do_checkpoint(bs, errp);
     }
     aio_context_release(aio_context);
 }
@@ -652,8 +676,9 @@ static void replication_done(void *opaque, int ret)
     if (ret == 0) {
         s->stage = BLOCK_REPLICATION_DONE;
 
-        s->active_disk = NULL;
+        bdrv_unref_child(bs, s->secondary_disk);
         s->secondary_disk = NULL;
+        bdrv_unref_child(bs, s->hidden_disk);
         s->hidden_disk = NULL;
         s->error = 0;
     } else {
@@ -705,7 +730,7 @@ static void replication_stop(ReplicationState *rs, bool failover, Error **errp)
         }
 
         if (!failover) {
-            secondary_do_checkpoint(s, errp);
+            secondary_do_checkpoint(bs, errp);
             s->stage = BLOCK_REPLICATION_DONE;
             aio_context_release(aio_context);
             return;
@@ -713,7 +738,7 @@ static void replication_stop(ReplicationState *rs, bool failover, Error **errp)
 
         s->stage = BLOCK_REPLICATION_FAILOVER;
         s->commit_job = commit_active_start(
-                            NULL, s->active_disk->bs, s->secondary_disk->bs,
+                            NULL, bs->file->bs, s->secondary_disk->bs,
                             JOB_INTERNAL, 0, BLOCKDEV_ON_ERROR_REPORT,
                             NULL, replication_done, bs, true, errp);
         break;
diff --git a/block/vvfat.c b/block/vvfat.c
index ae9d387da7..34bf1e3a86 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -3098,26 +3098,6 @@ static int coroutine_fn vvfat_co_block_status(BlockDriverState *bs,
     return BDRV_BLOCK_DATA;
 }
 
-static int coroutine_fn
-write_target_commit(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
-                    QEMUIOVector *qiov, int flags)
-{
-    int ret;
-
-    BDRVVVFATState* s = *((BDRVVVFATState**) bs->opaque);
-    qemu_co_mutex_lock(&s->lock);
-    ret = try_commit(s);
-    qemu_co_mutex_unlock(&s->lock);
-
-    return ret;
-}
-
-static BlockDriver vvfat_write_target = {
-    .format_name        = "vvfat_write_target",
-    .instance_size      = sizeof(void*),
-    .bdrv_co_pwritev    = write_target_commit,
-};
-
 static void vvfat_qcow_options(BdrvChildRole role, bool parent_is_format,
                                int *child_flags, QDict *child_options,
                                int parent_flags, QDict *parent_options)
@@ -3133,7 +3113,6 @@ static int enable_write_target(BlockDriverState *bs, Error **errp)
 {
     BDRVVVFATState *s = bs->opaque;
     BlockDriver *bdrv_qcow = NULL;
-    BlockDriverState *backing;
     QemuOpts *opts = NULL;
     int ret;
     int size = sector2cluster(s, s->sector_count);
@@ -3184,13 +3163,6 @@ static int enable_write_target(BlockDriverState *bs, Error **errp)
     unlink(s->qcow_filename);
 #endif
 
-    backing = bdrv_new_open_driver(&vvfat_write_target, NULL, BDRV_O_ALLOW_RDWR,
-                                   &error_abort);
-    *(void**) backing->opaque = s;
-
-    bdrv_set_backing_hd(s->bs, backing, &error_abort);
-    bdrv_unref(backing);
-
     return 0;
 
 err:
@@ -3205,17 +3177,10 @@ static void vvfat_child_perm(BlockDriverState *bs, BdrvChild *c,
                              uint64_t perm, uint64_t shared,
                              uint64_t *nperm, uint64_t *nshared)
 {
-    if (role & BDRV_CHILD_DATA) {
-        /* This is a private node, nobody should try to attach to it */
-        *nperm = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
-        *nshared = BLK_PERM_WRITE_UNCHANGED;
-    } else {
-        assert(role & BDRV_CHILD_COW);
-        /* The backing file is there so 'commit' can use it. vvfat doesn't
-         * access it in any way. */
-        *nperm = 0;
-        *nshared = BLK_PERM_ALL;
-    }
+    assert(role & BDRV_CHILD_DATA);
+    /* This is a private node, nobody should try to attach to it */
+    *nperm = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
+    *nshared = BLK_PERM_WRITE_UNCHANGED;
 }
 
 static void vvfat_close(BlockDriverState *bs)
diff --git a/configure b/configure
index 63f38fa94c..232c54dcc1 100755
--- a/configure
+++ b/configure
@@ -243,6 +243,7 @@ cross_prefix=""
 audio_drv_list=""
 block_drv_rw_whitelist=""
 block_drv_ro_whitelist=""
+block_drv_whitelist_tools="no"
 host_cc="cc"
 audio_win_int=""
 libs_qga=""
@@ -1016,6 +1017,10 @@ for opt do
   ;;
   --block-drv-ro-whitelist=*) block_drv_ro_whitelist=$(echo "$optarg" | sed -e 's/,/ /g')
   ;;
+  --enable-block-drv-whitelist-in-tools) block_drv_whitelist_tools="yes"
+  ;;
+  --disable-block-drv-whitelist-in-tools) block_drv_whitelist_tools="no"
+  ;;
   --enable-debug-tcg) debug_tcg="yes"
   ;;
   --disable-debug-tcg) debug_tcg="no"
@@ -1800,10 +1805,12 @@ Advanced options (experts only):
   --block-drv-whitelist=L  Same as --block-drv-rw-whitelist=L
   --block-drv-rw-whitelist=L
                            set block driver read-write whitelist
-                           (affects only QEMU, not qemu-img)
+                           (by default affects only QEMU, not tools like qemu-img)
   --block-drv-ro-whitelist=L
                            set block driver read-only whitelist
-                           (affects only QEMU, not qemu-img)
+                           (by default affects only QEMU, not tools like qemu-img)
+  --enable-block-drv-whitelist-in-tools
+                           use block whitelist also in tools instead of only QEMU
   --enable-trace-backends=B Set trace backend
                            Available backends: $trace_backend_list
   --with-trace-file=NAME   Full PATH,NAME of file to store traces
@@ -4583,6 +4590,9 @@ if test "$audio_win_int" = "yes" ; then
 fi
 echo "CONFIG_BDRV_RW_WHITELIST=$block_drv_rw_whitelist" >> $config_host_mak
 echo "CONFIG_BDRV_RO_WHITELIST=$block_drv_ro_whitelist" >> $config_host_mak
+if test "$block_drv_whitelist_tools" = "yes" ; then
+  echo "CONFIG_BDRV_WHITELIST_TOOLS=y" >> $config_host_mak
+fi
 if test "$xfs" = "yes" ; then
   echo "CONFIG_XFS=y" >> $config_host_mak
 fi
diff --git a/meson.build b/meson.build
index 6e4d2d8034..2f377098d7 100644
--- a/meson.build
+++ b/meson.build
@@ -2996,6 +2996,7 @@ summary_info += {'coroutine pool':    config_host['CONFIG_COROUTINE_POOL'] == '1
 if have_block
   summary_info += {'Block whitelist (rw)': config_host['CONFIG_BDRV_RW_WHITELIST']}
   summary_info += {'Block whitelist (ro)': config_host['CONFIG_BDRV_RO_WHITELIST']}
+  summary_info += {'Use block whitelist in tools': config_host.has_key('CONFIG_BDRV_WHITELIST_TOOLS')}
   summary_info += {'VirtFS support':    have_virtfs}
   summary_info += {'build virtiofs daemon': have_virtiofsd}
   summary_info += {'Live block migration': config_host.has_key('CONFIG_LIVE_BLOCK_MIGRATION')}
diff --git a/tests/qemu-iotests/151 b/tests/qemu-iotests/151
index 182f6b5321..93d14193d0 100755
--- a/tests/qemu-iotests/151
+++ b/tests/qemu-iotests/151
@@ -38,8 +38,9 @@ class TestActiveMirror(iotests.QMPTestCase):
                       'if': 'none',
                       'node-name': 'source-node',
                       'driver': iotests.imgfmt,
-                      'file': {'driver': 'file',
-                               'filename': source_img}}
+                      'file': {'driver': 'blkdebug',
+                               'image': {'driver': 'file',
+                                         'filename': source_img}}}
 
         blk_target = {'node-name': 'target-node',
                       'driver': iotests.imgfmt,
@@ -141,6 +142,55 @@ class TestActiveMirror(iotests.QMPTestCase):
 
         self.potential_writes_in_flight = False
 
+    def testIntersectingActiveIO(self):
+        # Fill the source image
+        result = self.vm.hmp_qemu_io('source', 'write -P 1 0 2M')
+
+        # Start the block job (very slowly)
+        result = self.vm.qmp('blockdev-mirror',
+                             job_id='mirror',
+                             filter_node_name='mirror-node',
+                             device='source-node',
+                             target='target-node',
+                             sync='full',
+                             copy_mode='write-blocking',
+                             speed=1)
+
+        self.vm.hmp_qemu_io('source', 'break write_aio A')
+        self.vm.hmp_qemu_io('source', 'aio_write 0 1M')  # 1
+        self.vm.hmp_qemu_io('source', 'wait_break A')
+        self.vm.hmp_qemu_io('source', 'aio_write 0 2M')  # 2
+        self.vm.hmp_qemu_io('source', 'aio_write 0 2M')  # 3
+
+        # Now 2 and 3 are in mirror_wait_on_conflicts, waiting for 1
+
+        self.vm.hmp_qemu_io('source', 'break write_aio B')
+        self.vm.hmp_qemu_io('source', 'aio_write 1M 2M')  # 4
+        self.vm.hmp_qemu_io('source', 'wait_break B')
+
+        # 4 doesn't wait for 2 and 3, because they didn't yet set
+        # in_flight_bitmap. So, nothing prevents 4 to go except for our
+        # break-point B.
+
+        self.vm.hmp_qemu_io('source', 'resume A')
+
+        # Now we resumed 1, so 2 and 3 goes to the next iteration of while loop
+        # in mirror_wait_on_conflicts(). They don't exit, as bitmap is dirty
+        # due to request 4.
+        # In the past at that point 2 and 3 would wait for each other producing
+        # a dead-lock. Now this is fixed and they will wait for request 4.
+
+        self.vm.hmp_qemu_io('source', 'resume B')
+
+        # After resuming 4, one of 2 and 3 goes first and set in_flight_bitmap,
+        # so the other will wait for it.
+
+        result = self.vm.qmp('block-job-set-speed', device='mirror', speed=0)
+        self.assert_qmp(result, 'return', {})
+        self.complete_and_wait(drive='mirror')
+
+        self.potential_writes_in_flight = False
+
 
 if __name__ == '__main__':
     iotests.main(supported_fmts=['qcow2', 'raw'],
diff --git a/tests/qemu-iotests/151.out b/tests/qemu-iotests/151.out
index 8d7e996700..89968f35d7 100644
--- a/tests/qemu-iotests/151.out
+++ b/tests/qemu-iotests/151.out
@@ -1,5 +1,5 @@
-...
+....
 ----------------------------------------------------------------------
-Ran 3 tests
+Ran 4 tests
 
 OK
diff --git a/tests/qemu-iotests/307 b/tests/qemu-iotests/307
index c7685347bc..b429b5aa50 100755
--- a/tests/qemu-iotests/307
+++ b/tests/qemu-iotests/307
@@ -41,9 +41,11 @@ with iotests.FilePath('image') as img, \
     iotests.log('=== Launch VM ===')
 
     vm.add_object('iothread,id=iothread0')
+    vm.add_object('iothread,id=iothread1')
     vm.add_blockdev(f'file,filename={img},node-name=file')
     vm.add_blockdev(f'{iotests.imgfmt},file=file,node-name=fmt')
     vm.add_blockdev('raw,file=file,node-name=ro,read-only=on')
+    vm.add_blockdev('null-co,node-name=null')
     vm.add_device(f'id=scsi0,driver=virtio-scsi,iothread=iothread0')
     vm.launch()
 
@@ -74,6 +76,19 @@ with iotests.FilePath('image') as img, \
     vm.qmp_log('query-block-exports')
     iotests.qemu_nbd_list_log('-k', socket)
 
+    iotests.log('\n=== Add export with conflicting iothread ===')
+
+    vm.qmp_log('device_add', id='sdb', driver='scsi-hd', drive='null')
+
+    # Should fail because of fixed-iothread
+    vm.qmp_log('block-export-add', id='export1', type='nbd', node_name='null',
+               iothread='iothread1', fixed_iothread=True, writable=True)
+
+    # Should ignore the iothread conflict, but then fail because of the
+    # permission conflict (and not crash)
+    vm.qmp_log('block-export-add', id='export1', type='nbd', node_name='null',
+               iothread='iothread1', fixed_iothread=False, writable=True)
+
     iotests.log('\n=== Add a writable export ===')
 
     # This fails because share-rw=off
diff --git a/tests/qemu-iotests/307.out b/tests/qemu-iotests/307.out
index 4b0c7e155a..ec8d2be0e0 100644
--- a/tests/qemu-iotests/307.out
+++ b/tests/qemu-iotests/307.out
@@ -51,6 +51,14 @@ exports available: 1
    base:allocation
 
 
+=== Add export with conflicting iothread ===
+{"execute": "device_add", "arguments": {"drive": "null", "driver": "scsi-hd", "id": "sdb"}}
+{"return": {}}
+{"execute": "block-export-add", "arguments": {"fixed-iothread": true, "id": "export1", "iothread": "iothread1", "node-name": "null", "type": "nbd", "writable": true}}
+{"error": {"class": "GenericError", "desc": "Cannot change iothread of active block backend"}}
+{"execute": "block-export-add", "arguments": {"fixed-iothread": false, "id": "export1", "iothread": "iothread1", "node-name": "null", "type": "nbd", "writable": true}}
+{"error": {"class": "GenericError", "desc": "Permission conflict on node 'null': permissions 'write' are both required by an unnamed block device (uses node 'null' as 'root' child) and unshared by block device 'sdb' (uses node 'null' as 'root' child)."}}
+
 === Add a writable export ===
 {"execute": "block-export-add", "arguments": {"description": "This is the writable second export", "id": "export1", "name": "export1", "node-name": "fmt", "type": "nbd", "writable": true, "writethrough": true}}
 {"error": {"class": "GenericError", "desc": "Permission conflict on node 'fmt': permissions 'write' are both required by an unnamed block device (uses node 'fmt' as 'root' child) and unshared by block device 'sda' (uses node 'fmt' as 'root' child)."}}