[Qemu-devel] [PATCH v9 00/11] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD

[Qemu-devel] [PATCH v9 00/11] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD

[Fam Zheng]

This series adds for point-in-time snapshot NBD exporting based on
blockdev-backup (variant of drive-backup with existing device as target).

We get a thin point-in-time snapshot by COW mechanism of drive-backup, and
export it through built in NBD server. The steps are as below:

 1. (SHELL) qemu-img create -f qcow2 BACKUP.qcow2 <source size here>

    (Alternatively we can use -o backing_file=RUNNING-VM.img to omit explicitly
    providing the size by ourselves, but it's risky because RUNNING-VM.qcow2 is
    used r/w by guest. Whether or not setting backing file in the image file
    doesn't matter, as we are going to override the backing hd in the next
    step)

 2. (QMP) blockdev-add backing=source-drive file.driver=file file.filename=BACKUP.qcow2 id=target0 if=none driver=qcow2

    (where source-drive is the running BlockDriverState name for
    RUNNING-VM.img. This patch implements "backing=" option to override
    backing_hd for added drive)

 3. (QMP) blockdev-backup device=source-drive sync=none target=target0

    (this is the QMP command introduced by this series, which use a named
    device as target of drive-backup)

 4. (QMP) nbd-server-add device=target0

When image fleecing done:

 1. (QMP) block-job-cancel device=source-drive

 2. (HMP) drive_del target0

 3. (SHELL) rm BACKUP.qcow2

v9: Rebased to qemu.git. Address Stefan's comments:

    [05/11] block: Add bdrv_set_backing_hd()
            Set bs->backing_file and bs->backing_format.

    [06/11] block: Add backing_blocker in BlockDriverState
            Reuse bdrv_set_backing_hd().

    [07/11] block: Parse "backing" option to reference existing BDS
            Fix use-after-free.
            Check for "backing=" and "backing.file=" conflict.
            Remove unintended bdrv_swap hunks.

    [08/11] block: Support dropping active in bdrv_drop_intermediate
            Fix function comment.

    [09/11] stream: Use bdrv_drop_intermediate and drop close_unused_images



Fam Zheng (11):
  qapi: Add BlockOperationType enum
  block: Introduce op_blockers to BlockDriverState
  block: Replace in_use with operation blocker
  block: Move op_blocker check from block_job_create to its caller
  block: Add bdrv_set_backing_hd()
  block: Add backing_blocker in BlockDriverState
  block: Parse "backing" option to reference existing BDS
  block: Support dropping active in bdrv_drop_intermediate
  stream: Use bdrv_drop_intermediate and drop close_unused_images
  qmp: Add command 'blockdev-backup'
  block: Allow backup on referenced named BlockDriverState

 block-migration.c               |   7 +-
 block.c                         | 306 +++++++++++++++++++++++++++-------------
 block/backup.c                  |  21 +++
 block/commit.c                  |   1 +
 block/stream.c                  |  28 +---
 blockdev.c                      |  70 +++++++--
 blockjob.c                      |  14 +-
 hw/block/dataplane/virtio-blk.c |  19 ++-
 include/block/block.h           |  10 +-
 include/block/block_int.h       |   9 +-
 include/block/blockjob.h        |   3 +
 qapi-schema.json                |  99 +++++++++++++
 qmp-commands.hx                 |  44 ++++++
 13 files changed, 477 insertions(+), 154 deletions(-)

-- 
1.8.5.1

[Qemu-devel] [PATCH v9 01/11] qapi: Add BlockOperationType enum

[Fam Zheng]

This adds the enum of all the operations that can be taken on a block
device.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 qapi-schema.json | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/qapi-schema.json b/qapi-schema.json
index c3c939c..288d024 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1440,6 +1440,56 @@
   'data': ['commit', 'stream', 'mirror', 'backup'] }
 
 ##
+# @BlockOperationType
+#
+# Type of a block operation. (since 2.0)
+#
+# @backup-source: As a backup source. See the 'drive-backup' command.
+#
+# @backup-target: As a backup target. See the 'drive-backup' command.
+#
+# @change: See the 'change' command.
+#
+# @commit: See the 'block-commit' command.
+#
+# @dataplane: The virtio-blk dataplane feature.
+#
+# @drive-del: See the 'drive_del' HMP command.
+#
+# @eject: See the 'eject' command.
+#
+# @external-snapshot: See the 'blockdev-snapshot-sync' command.
+#
+# @internal-snapshot: See the 'blockdev-snapshot-internal-sync' command.
+#
+# @internal-snapshot-delete: See the 'blockdev-snapshot-delete-internal-sync' command.
+#
+# @mirror: See the 'drive-mirror' command.
+#
+# @resize: See the 'block-resize' command.
+#
+# @stream: See the 'block-stream' command.
+#
+# Since: 2.0
+##
+{ 'enum': 'BlockOpType',
+  'data': [
+    'backup-source',
+    'backup-target',
+    'change',
+    'commit',
+    'dataplane',
+    'drive-del',
+    'eject',
+    'external-snapshot',
+    'internal-snapshot',
+    'internal-snapshot-delete',
+    'mirror',
+    'resize',
+    'stream'
+] }
+
+##
 # @BlockJobInfo:
 #
 # Information about a long-running block device operation.
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 02/11] block: Introduce op_blockers to BlockDriverState

[Fam Zheng]

BlockDriverState.op_blockers is an array of lists with BLOCK_OP_TYPE_MAX
elements. Each list is a list of blockers of an operation type
(BlockOpType), that marks this BDS as currently blocked for a certain
type of operation with reason errors stored in the list. The rule of
usage is:

 * BDS user who wants to take an operation should check if there's any
   blocker of the type with bdrv_op_is_blocked().

 * BDS user who wants to block certain types of operation, should call
   bdrv_op_block (or bdrv_op_block_all to block all types of operations,
   which is similar to the existing bdrv_set_in_use()).

 * A blocker is only referenced by op_blockers, so the lifecycle is
   managed by caller, and shouldn't be lost until unblock, so typically
   a caller does these:

   - Allocate a blocker with error_setg or similar, call bdrv_op_block()
     to block some operations.
   - Hold the blocker, do his job.
   - Unblock operations that it blocked, with the same reason pointer
     passed to bdrv_op_unblock().
   - Release the blocker with error_free().

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c                   | 71 +++++++++++++++++++++++++++++++++++++++++++++++
 include/block/block.h     |  7 +++++
 include/block/block_int.h |  5 ++++
 3 files changed, 83 insertions(+)

diff --git a/block.c b/block.c
index 64e7d22..91cda9c 100644
--- a/block.c
+++ b/block.c
@@ -1627,6 +1627,8 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     /* keep the same entry in bdrv_states */
     pstrcpy(bs_dest->device_name, sizeof(bs_dest->device_name),
             bs_src->device_name);
+    memcpy(bs_dest->op_blockers, bs_src->op_blockers,
+           sizeof(bs_dest->op_blockers));
     bs_dest->list = bs_src->list;
 }
 
@@ -4634,6 +4636,75 @@ void bdrv_unref(BlockDriverState *bs)
     }
 }
 
+struct BdrvOpBlocker {
+    Error *reason;
+    QLIST_ENTRY(BdrvOpBlocker) list;
+};
+
+bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp)
+{
+    BdrvOpBlocker *blocker;
+    assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
+    if (!QLIST_EMPTY(&bs->op_blockers[op])) {
+        blocker = QLIST_FIRST(&bs->op_blockers[op]);
+        if (errp) {
+            *errp = error_copy(blocker->reason);
+        }
+        return true;
+    }
+    return false;
+}
+
+void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason)
+{
+    BdrvOpBlocker *blocker;
+    assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
+
+    blocker = g_malloc0(sizeof(BdrvOpBlocker));
+    blocker->reason = reason;
+    QLIST_INSERT_HEAD(&bs->op_blockers[op], blocker, list);
+}
+
+void bdrv_op_unblock(BlockDriverState *bs, BlockOpType op, Error *reason)
+{
+    BdrvOpBlocker *blocker, *next;
+    assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
+    QLIST_FOREACH_SAFE(blocker, &bs->op_blockers[op], list, next) {
+        if (blocker->reason == reason) {
+            QLIST_REMOVE(blocker, list);
+            g_free(blocker);
+        }
+    }
+}
+
+void bdrv_op_block_all(BlockDriverState *bs, Error *reason)
+{
+    int i;
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        bdrv_op_block(bs, i, reason);
+    }
+}
+
+void bdrv_op_unblock_all(BlockDriverState *bs, Error *reason)
+{
+    int i;
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        bdrv_op_unblock(bs, i, reason);
+    }
+}
+
+bool bdrv_op_blocker_is_empty(BlockDriverState *bs)
+{
+    int i;
+
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        if (!QLIST_EMPTY(&bs->op_blockers[i])) {
+            return false;
+        }
+    }
+    return true;
+}
+
 void bdrv_set_in_use(BlockDriverState *bs, int in_use)
 {
     assert(bs->in_use != in_use);
diff --git a/include/block/block.h b/include/block/block.h
index 36efaea..890af1a 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -442,6 +442,13 @@ void bdrv_unref(BlockDriverState *bs);
 void bdrv_set_in_use(BlockDriverState *bs, int in_use);
 int bdrv_in_use(BlockDriverState *bs);
 
+bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp);
+void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason);
+void bdrv_op_unblock(BlockDriverState *bs, BlockOpType op, Error *reason);
+void bdrv_op_block_all(BlockDriverState *bs, Error *reason);
+void bdrv_op_unblock_all(BlockDriverState *bs, Error *reason);
+bool bdrv_op_blocker_is_empty(BlockDriverState *bs);
+
 #ifdef CONFIG_LINUX_AIO
 int raw_get_aio_fd(BlockDriverState *bs);
 #else
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 8b132d7..458acd6 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -252,6 +252,8 @@ typedef struct BlockLimits {
     int opt_transfer_length;
 } BlockLimits;
 
+typedef struct BdrvOpBlocker BdrvOpBlocker;
+
 /*
  * Note: the function bdrv_append() copies and swaps contents of
  * BlockDriverStates, so if you add new fields to this struct, please
@@ -333,6 +335,9 @@ struct BlockDriverState {
 
     QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
 
+    /* operation blockers */
+    QLIST_HEAD(, BdrvOpBlocker) op_blockers[BLOCK_OP_TYPE_MAX];
+
     /* long-running background operation */
     BlockJob *job;
 
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 03/11] block: Replace in_use with operation blocker

[Fam Zheng]

This drops BlockDriverState.in_use with op_blockers:

  - Call bdrv_op_block_all in place of bdrv_set_in_use(bs, 1).
  - Call bdrv_op_unblock_all in place of bdrv_set_in_use(bs, 0).
  - Check bdrv_op_is_blocked() in place of bdrv_in_use(bs).
    The specific types are used, e.g. in place of starting block backup,
    bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP, ...).
  - Check bdrv_op_blocker_is_empty() in place of assert(!bs->in_use).

Note: there is only bdrv_op_block_all and bdrv_op_unblock_all callers at
this moment. So although the checks are specific to op types, this
changes can still be seen as identical logic with previously with
in_use. The difference is error message are improved because of blocker
error info.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block-migration.c               |  7 +++++--
 block.c                         | 24 +++++++-----------------
 blockdev.c                      | 15 ++++++---------
 blockjob.c                      | 14 +++++++++-----
 hw/block/dataplane/virtio-blk.c | 19 ++++++++++++-------
 include/block/block.h           |  2 --
 include/block/block_int.h       |  1 -
 include/block/blockjob.h        |  3 +++
 8 files changed, 42 insertions(+), 43 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 897fdba..bf9a25f 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -59,6 +59,7 @@ typedef struct BlkMigDevState {
     unsigned long *aio_bitmap;
     int64_t completed_sectors;
     BdrvDirtyBitmap *dirty_bitmap;
+    Error *blocker;
 } BlkMigDevState;
 
 typedef struct BlkMigBlock {
@@ -346,7 +347,8 @@ static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
         bmds->completed_sectors = 0;
         bmds->shared_base = block_mig_state.shared_base;
         alloc_aio_bitmap(bmds);
-        bdrv_set_in_use(bs, 1);
+        error_setg(&bmds->blocker, "block device is in use by migration");
+        bdrv_op_block_all(bs, bmds->blocker);
         bdrv_ref(bs);
 
         block_mig_state.total_sector_sum += sectors;
@@ -584,7 +586,8 @@ static void blk_mig_cleanup(void)
     blk_mig_lock();
     while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
-        bdrv_set_in_use(bmds->bs, 0);
+        bdrv_op_unblock_all(bmds->bs, bmds->blocker);
+        error_free(bmds->blocker);
         bdrv_unref(bmds->bs);
         g_free(bmds->aio_bitmap);
         g_free(bmds);
diff --git a/block.c b/block.c
index 91cda9c..b122154 100644
--- a/block.c
+++ b/block.c
@@ -1621,7 +1621,6 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     bs_dest->refcnt             = bs_src->refcnt;
 
     /* job */
-    bs_dest->in_use             = bs_src->in_use;
     bs_dest->job                = bs_src->job;
 
     /* keep the same entry in bdrv_states */
@@ -1653,7 +1652,7 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
     assert(QLIST_EMPTY(&bs_new->dirty_bitmaps));
     assert(bs_new->job == NULL);
     assert(bs_new->dev == NULL);
-    assert(bs_new->in_use == 0);
+    assert(bdrv_op_blocker_is_empty(bs_new));
     assert(bs_new->io_limits_enabled == false);
     assert(!throttle_have_timer(&bs_new->throttle_state));
 
@@ -1672,7 +1671,7 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
     /* Check a few fields that should remain attached to the device */
     assert(bs_new->dev == NULL);
     assert(bs_new->job == NULL);
-    assert(bs_new->in_use == 0);
+    assert(bdrv_op_blocker_is_empty(bs_new));
     assert(bs_new->io_limits_enabled == false);
     assert(!throttle_have_timer(&bs_new->throttle_state));
 
@@ -1709,7 +1708,7 @@ static void bdrv_delete(BlockDriverState *bs)
 {
     assert(!bs->dev);
     assert(!bs->job);
-    assert(!bs->in_use);
+    assert(bdrv_op_blocker_is_empty(bs));
     assert(!bs->refcnt);
     assert(QLIST_EMPTY(&bs->dirty_bitmaps));
 
@@ -1891,7 +1890,8 @@ int bdrv_commit(BlockDriverState *bs)
         return -ENOTSUP;
     }
 
-    if (bdrv_in_use(bs) || bdrv_in_use(bs->backing_hd)) {
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT, NULL) ||
+        bdrv_op_is_blocked(bs->backing_hd, BLOCK_OP_TYPE_COMMIT, NULL)) {
         return -EBUSY;
     }
 
@@ -2924,8 +2924,9 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset)
         return -ENOTSUP;
     if (bs->read_only)
         return -EACCES;
-    if (bdrv_in_use(bs))
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_RESIZE, NULL)) {
         return -EBUSY;
+    }
     ret = drv->bdrv_truncate(bs, offset);
     if (ret == 0) {
         ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
@@ -4705,17 +4706,6 @@ bool bdrv_op_blocker_is_empty(BlockDriverState *bs)
     return true;
 }
 
-void bdrv_set_in_use(BlockDriverState *bs, int in_use)
-{
-    assert(bs->in_use != in_use);
-    bs->in_use = in_use;
-}
-
-int bdrv_in_use(BlockDriverState *bs)
-{
-    return bs->in_use;
-}
-
 void bdrv_iostatus_enable(BlockDriverState *bs)
 {
     bs->iostatus_enabled = true;
diff --git a/blockdev.c b/blockdev.c
index 6a85961..9d36775 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1224,8 +1224,8 @@ static void external_snapshot_prepare(BlkTransactionState *common,
         return;
     }
 
-    if (bdrv_in_use(state->old_bs)) {
-        error_set(errp, QERR_DEVICE_IN_USE, device);
+    if (bdrv_op_is_blocked(state->old_bs,
+                           BLOCK_OP_TYPE_EXTERNAL_SNAPSHOT, errp)) {
         return;
     }
 
@@ -1441,8 +1441,7 @@ exit:
 
 static void eject_device(BlockDriverState *bs, int force, Error **errp)
 {
-    if (bdrv_in_use(bs)) {
-        error_set(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_EJECT, errp)) {
         return;
     }
     if (!bdrv_dev_has_removable_media(bs)) {
@@ -1643,7 +1642,7 @@ int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
         qerror_report(QERR_DEVICE_NOT_FOUND, id);
         return -1;
     }
-    if (bdrv_in_use(bs)) {
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, NULL)) {
         qerror_report(QERR_DEVICE_IN_USE, id);
         return -1;
     }
@@ -1881,8 +1880,7 @@ void qmp_drive_backup(const char *device, const char *target,
         }
     }
 
-    if (bdrv_in_use(bs)) {
-        error_set(errp, QERR_DEVICE_IN_USE, device);
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
         return;
     }
 
@@ -2011,8 +2009,7 @@ void qmp_drive_mirror(const char *device, const char *target,
         }
     }
 
-    if (bdrv_in_use(bs)) {
-        error_set(errp, QERR_DEVICE_IN_USE, device);
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_MIRROR, errp)) {
         return;
     }
 
diff --git a/blockjob.c b/blockjob.c
index 9e5fd5c..f1ff036 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -41,14 +41,16 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
 {
     BlockJob *job;
 
-    if (bs->job || bdrv_in_use(bs)) {
+    if (bs->job || !bdrv_op_blocker_is_empty(bs)) {
         error_set(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
         return NULL;
     }
     bdrv_ref(bs);
-    bdrv_set_in_use(bs, 1);
-
     job = g_malloc0(driver->instance_size);
+    error_setg(&job->blocker, "block device is in use by block job: %s",
+               BlockJobType_lookup[driver->job_type]);
+    bdrv_op_block_all(bs, job->blocker);
+
     job->driver        = driver;
     job->bs            = bs;
     job->cb            = cb;
@@ -63,8 +65,9 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
         block_job_set_speed(job, speed, &local_err);
         if (error_is_set(&local_err)) {
             bs->job = NULL;
+            bdrv_op_unblock_all(bs, job->blocker);
+            error_free(job->blocker);
             g_free(job);
-            bdrv_set_in_use(bs, 0);
             error_propagate(errp, local_err);
             return NULL;
         }
@@ -79,8 +82,9 @@ void block_job_completed(BlockJob *job, int ret)
     assert(bs->job == job);
     job->cb(job->opaque, ret);
     bs->job = NULL;
+    bdrv_op_unblock_all(bs, job->blocker);
+    error_free(job->blocker);
     g_free(job);
-    bdrv_set_in_use(bs, 0);
 }
 
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 1e57f3a..3fb7f82 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -69,6 +69,9 @@ struct VirtIOBlockDataPlane {
                                              queue */
 
     unsigned int num_reqs;
+
+    /* Operation blocker on BDS */
+    Error *blocker;
 };
 
 /* Raise an interrupt to signal guest, if necessary */
@@ -386,6 +389,7 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
 {
     VirtIOBlockDataPlane *s;
     int fd;
+    Error *local_err = NULL;
 
     *dataplane = NULL;
 
@@ -408,9 +412,10 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
     /* If dataplane is (re-)enabled while the guest is running there could be
      * block jobs that can conflict.
      */
-    if (bdrv_in_use(blk->conf.bs)) {
-        error_setg(errp,
-                   "cannot start dataplane thread while device is in use");
+    if (bdrv_op_is_blocked(blk->conf.bs, BLOCK_OP_TYPE_DATAPLANE, &local_err)) {
+        error_report("cannot start dataplane thread: %s",
+                      error_get_pretty(local_err));
+        error_free(local_err);
         return;
     }
 
@@ -425,9 +430,8 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
     s->vdev = vdev;
     s->fd = fd;
     s->blk = blk;
-
-    /* Prevent block operations that conflict with data plane thread */
-    bdrv_set_in_use(blk->conf.bs, 1);
+    error_setg(&s->blocker, "block device is in use by data plane");
+    bdrv_op_block_all(blk->conf.bs, s->blocker);
 
     *dataplane = s;
 }
@@ -439,7 +443,8 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
     }
 
     virtio_blk_data_plane_stop(s);
-    bdrv_set_in_use(s->blk->conf.bs, 0);
+    bdrv_op_unblock_all(s->blk->conf.bs, s->blocker);
+    error_free(s->blocker);
     g_free(s);
 }
 
diff --git a/include/block/block.h b/include/block/block.h
index 890af1a..ac8976e 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -439,8 +439,6 @@ void bdrv_disable_copy_on_read(BlockDriverState *bs);
 
 void bdrv_ref(BlockDriverState *bs);
 void bdrv_unref(BlockDriverState *bs);
-void bdrv_set_in_use(BlockDriverState *bs, int in_use);
-int bdrv_in_use(BlockDriverState *bs);
 
 bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp);
 void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 458acd6..2f6556d 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -330,7 +330,6 @@ struct BlockDriverState {
     char device_name[32];
     QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
     int refcnt;
-    int in_use; /* users other than guest access, eg. block migration */
     QTAILQ_ENTRY(BlockDriverState) list;
 
     QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index d76de62..c0a7875 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -106,6 +106,9 @@ struct BlockJob {
     /** The completion function that will be called when the job completes.  */
     BlockDriverCompletionFunc *cb;
 
+    /** Block other operations when block job is running */
+    Error *blocker;
+
     /** The opaque value that is passed to the completion function.  */
     void *opaque;
 };
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 04/11] block: Move op_blocker check from block_job_create to its caller

[Fam Zheng]

It makes no sense to check for "any" blocker on bs, we are here only
because of the mechanical conversion from in_use to op_blockers. Remove
it now, and let the callers check specific operation types. Backup and
mirror already have it, add checker to stream and commit.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 blockdev.c | 8 ++++++++
 blockjob.c | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 9d36775..7f305d8 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1754,6 +1754,10 @@ void qmp_block_stream(const char *device, bool has_base,
         return;
     }
 
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_STREAM, errp)) {
+        return;
+    }
+
     if (base) {
         base_bs = bdrv_find_backing_image(bs, base);
         if (base_bs == NULL) {
@@ -1794,6 +1798,10 @@ void qmp_block_commit(const char *device,
         return;
     }
 
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT, errp)) {
+        return;
+    }
+
     /* default top_bs is the active layer */
     top_bs = bs;
 
diff --git a/blockjob.c b/blockjob.c
index f1ff036..21e21c0 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -41,7 +41,7 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
 {
     BlockJob *job;
 
-    if (bs->job || !bdrv_op_blocker_is_empty(bs)) {
+    if (bs->job) {
         error_set(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
         return NULL;
     }
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 05/11] block: Add bdrv_set_backing_hd()

[Fam Zheng]

This is the common but non-trivial steps to assign or change the
backing_hd of BDS.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c               | 34 ++++++++++++++++++++++++++++------
 include/block/block.h |  1 +
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/block.c b/block.c
index b122154..ff25749 100644
--- a/block.c
+++ b/block.c
@@ -958,6 +958,29 @@ fail:
     return ret;
 }
 
+void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
+{
+    if (bs->backing_hd) {
+        bdrv_unref(bs->backing_hd);
+    }
+
+    bs->backing_hd = backing_hd;
+    if (!backing_hd) {
+        bs->backing_file[0] = '\0';
+        bs->backing_format[0] = '\0';
+        return;
+    }
+    pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_hd->filename);
+    pstrcpy(bs->backing_format, sizeof(bs->backing_file),
+            backing_hd->drv ? backing_hd->drv->format_name : "");
+    bdrv_ref(bs->backing_hd);
+
+    pstrcpy(bs->backing_file, sizeof(bs->backing_file),
+            bs->backing_hd->file->filename);
+    pstrcpy(bs->backing_format, sizeof(bs->backing_format),
+            bs->backing_hd->drv->format_name);
+}
+
 /*
  * Opens the backing file for a BlockDriverState if not yet open
  *
@@ -971,6 +994,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
     char backing_filename[PATH_MAX];
     int back_flags, ret;
     BlockDriver *back_drv = NULL;
+    BlockDriverState *backing_hd;
     Error *local_err = NULL;
 
     if (bs->backing_hd != NULL) {
@@ -994,7 +1018,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
                                        sizeof(backing_filename));
     }
 
-    bs->backing_hd = bdrv_new("");
+    backing_hd = bdrv_new("");
 
     if (bs->backing_format[0] != '\0') {
         back_drv = bdrv_find_format(bs->backing_format);
@@ -1004,20 +1028,18 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
     back_flags = bs->open_flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT |
                                     BDRV_O_COPY_ON_READ);
 
-    ret = bdrv_open(bs->backing_hd,
+    ret = bdrv_open(backing_hd,
                     *backing_filename ? backing_filename : NULL, options,
                     back_flags, back_drv, &local_err);
     if (ret < 0) {
-        bdrv_unref(bs->backing_hd);
-        bs->backing_hd = NULL;
+        bdrv_unref(backing_hd);
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_setg(errp, "Could not open backing file: %s",
                    error_get_pretty(local_err));
         error_free(local_err);
         return ret;
     }
-    pstrcpy(bs->backing_file, sizeof(bs->backing_file),
-            bs->backing_hd->file->filename);
+    bdrv_set_backing_hd(bs, backing_hd);
     return 0;
 }
 
diff --git a/include/block/block.h b/include/block/block.h
index ac8976e..20bfcd9 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -185,6 +185,7 @@ int bdrv_parse_cache_flags(const char *mode, int *flags);
 int bdrv_parse_discard_flags(const char *mode, int *flags);
 int bdrv_file_open(BlockDriverState **pbs, const char *filename,
                    QDict *options, int flags, Error **errp);
+void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd);
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp);
 int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
               int flags, BlockDriver *drv, Error **errp);
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 06/11] block: Add backing_blocker in BlockDriverState

[Fam Zheng]

This makes use of op_blocker and blocks all the operations except for
commit target, on each BlockDriverState->backing_hd.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c                   | 16 ++++++++++++++--
 include/block/block_int.h |  3 +++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index ff25749..907c483 100644
--- a/block.c
+++ b/block.c
@@ -961,13 +961,22 @@ fail:
 void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
 {
     if (bs->backing_hd) {
+        assert(error_is_set(&bs->backing_blocker));
+        bdrv_op_unblock_all(bs->backing_hd, bs->backing_blocker);
         bdrv_unref(bs->backing_hd);
+    } else if (backing_hd) {
+        error_setg(&bs->backing_blocker,
+                   "device is used as backing hd of '%s'",
+                   bs->device_name);
     }
 
     bs->backing_hd = backing_hd;
     if (!backing_hd) {
         bs->backing_file[0] = '\0';
         bs->backing_format[0] = '\0';
+        if (error_is_set(&bs->backing_blocker)) {
+            error_free(bs->backing_blocker);
+        }
         return;
     }
     pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_hd->filename);
@@ -975,6 +984,10 @@ void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
             backing_hd->drv ? backing_hd->drv->format_name : "");
     bdrv_ref(bs->backing_hd);
 
+    bdrv_op_block_all(bs->backing_hd, bs->backing_blocker);
+    /* Otherwise we won't be able to commit due to check in bdrv_commit */
+    bdrv_op_unblock(bs->backing_hd, BLOCK_OP_TYPE_COMMIT,
+                    bs->backing_blocker);
     pstrcpy(bs->backing_file, sizeof(bs->backing_file),
             bs->backing_hd->file->filename);
     pstrcpy(bs->backing_format, sizeof(bs->backing_format),
@@ -1481,8 +1494,7 @@ void bdrv_close(BlockDriverState *bs)
 
     if (bs->drv) {
         if (bs->backing_hd) {
-            bdrv_unref(bs->backing_hd);
-            bs->backing_hd = NULL;
+            bdrv_set_backing_hd(bs, NULL);
         }
         bs->drv->bdrv_close(bs);
         g_free(bs->opaque);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 2f6556d..1ac17d5 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -341,6 +341,9 @@ struct BlockDriverState {
     BlockJob *job;
 
     QDict *options;
+
+    /* The error object in use for blocking operations on backing_hd */
+    Error *backing_blocker;
 };
 
 int get_tmp_filename(char *filename, int size);
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 07/11] block: Parse "backing" option to reference existing BDS

[Fam Zheng]

Now it's safe to allow reference for backing_hd in the interface.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index 907c483..618b8c3 100644
--- a/block.c
+++ b/block.c
@@ -1199,12 +1199,34 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
     /* If there is a backing file, use it */
     if ((flags & BDRV_O_NO_BACKING) == 0) {
         QDict *backing_options;
+        const char *backing_name;
+        BlockDriverState *backing_hd;
 
+        backing_name = qdict_get_try_str(options, "backing");
         qdict_extract_subqdict(options, &backing_options, "backing.");
-        ret = bdrv_open_backing_file(bs, backing_options, &local_err);
-        if (ret < 0) {
+
+        if (backing_name && qdict_size(backing_options)) {
+            error_setg(&local_err,
+                       "Option \"backing\" and \"backing.*\" cannot be "
+                       "used together");
+            ret = -EINVAL;
             goto close_and_fail;
         }
+        if (backing_name) {
+            backing_hd = bdrv_find(backing_name);
+            if (!backing_hd) {
+                error_set(&local_err, QERR_DEVICE_NOT_FOUND, backing_name);
+                ret = -ENOENT;
+                goto close_and_fail;
+            }
+            qdict_del(options, "backing");
+            bdrv_set_backing_hd(bs, backing_hd);
+        } else {
+            ret = bdrv_open_backing_file(bs, backing_options, &local_err);
+            if (ret < 0) {
+                goto close_and_fail;
+            }
+        }
     }
 
     /* Check if any unknown options were used */
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 08/11] block: Support dropping active in bdrv_drop_intermediate

[Fam Zheng]

Dropping intermediate could be useful both for commit and stream, and
BDS refcnt plus bdrv_swap could do most of the job nicely. It also needs
to work with op blockers.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c        | 145 ++++++++++++++++++++++++++-------------------------------
 block/commit.c |   1 +
 2 files changed, 66 insertions(+), 80 deletions(-)

diff --git a/block.c b/block.c
index 618b8c3..b28fb93 100644
--- a/block.c
+++ b/block.c
@@ -2190,114 +2190,99 @@ BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
     return overlay;
 }
 
-typedef struct BlkIntermediateStates {
-    BlockDriverState *bs;
-    QSIMPLEQ_ENTRY(BlkIntermediateStates) entry;
-} BlkIntermediateStates;
-
-
 /*
- * Drops images above 'base' up to and including 'top', and sets the image
- * above 'top' to have base as its backing file.
+ * Drops images above 'base' up to and including 'top', and sets new 'base'
+ * as backing_hd of top_overlay (the image orignally has 'top' as backing
+ * file). top_overlay may be NULL if 'top' is active, no such update needed.
+ * Requires that the top_overlay to 'top' is opened r/w.
  *
- * Requires that the overlay to 'top' is opened r/w, so that the backing file
- * information in 'bs' can be properly updated.
+ * 1) This will convert the following chain:
  *
- * E.g., this will convert the following chain:
- * bottom <- base <- intermediate <- top <- active
+ *     ... <- base <- ... <- top <- overlay <-... <- active
  *
  * to
  *
- * bottom <- base <- active
+ *     ... <- base <- overlay <- active
  *
- * It is allowed for bottom==base, in which case it converts:
+ * 2) It is allowed for bottom==base, in which case it converts:
  *
- * base <- intermediate <- top <- active
+ *     base <- ... <- top <- overlay <- ... <- active
  *
  * to
  *
- * base <- active
+ *     base <- overlay <- active
+ *
+ * 2) It also allows active==top, in which case it converts:
+ *
+ *     ... <- base <- ... <- top (active)
+ *
+ * to
+ *
+ *     ... <- base == active == top
+ *
+ * i.e. only base and lower remains: *top == *base when return.
+ *
+ * 3) If base==NULL, it will drop all the BDS below overlay and set its
+ * backing_hd to NULL. I.e.:
+ *
+ *     base(NULL) <- ... <- overlay <- ... <- active
+ *
+ * to
  *
- * Error conditions:
- *  if active == top, that is considered an error
+ *     overlay <- ... <- active
  *
  */
 int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top,
                            BlockDriverState *base)
 {
-    BlockDriverState *intermediate;
-    BlockDriverState *base_bs = NULL;
-    BlockDriverState *new_top_bs = NULL;
-    BlkIntermediateStates *intermediate_state, *next;
-    int ret = -EIO;
-
-    QSIMPLEQ_HEAD(states_to_delete, BlkIntermediateStates) states_to_delete;
-    QSIMPLEQ_INIT(&states_to_delete);
-
-    if (!top->drv || !base->drv) {
-        goto exit;
-    }
-
-    new_top_bs = bdrv_find_overlay(active, top);
+    BlockDriverState *drop_start, *overlay;
+    int ret = -EINVAL;
 
-    if (new_top_bs == NULL) {
-        /* we could not find the image above 'top', this is an error */
+    if (!top->drv || (base && !base->drv)) {
         goto exit;
     }
-
-    /* special case of new_top_bs->backing_hd already pointing to base - nothing
-     * to do, no intermediate images */
-    if (new_top_bs->backing_hd == base) {
+    if (top == base) {
         ret = 0;
-        goto exit;
-    }
-
-    intermediate = top;
-
-    /* now we will go down through the list, and add each BDS we find
-     * into our deletion queue, until we hit the 'base'
-     */
-    while (intermediate) {
-        intermediate_state = g_malloc0(sizeof(BlkIntermediateStates));
-        intermediate_state->bs = intermediate;
-        QSIMPLEQ_INSERT_TAIL(&states_to_delete, intermediate_state, entry);
-
-        if (intermediate->backing_hd == base) {
-            base_bs = intermediate->backing_hd;
-            break;
+    } else if (top == active) {
+        assert(base);
+        drop_start = active->backing_hd;
+        bdrv_swap(active, base);
+        base->backing_hd = NULL;
+        bdrv_unref(drop_start);
+        ret = 0;
+    } else {
+        /* If there's an overlay, its backing_hd points to top's BDS now,
+         * the top image is dropped but this BDS structure is kept and swapped
+         * with base, this way we keep the pointers valid after dropping top */
+        overlay = bdrv_find_overlay(active, top);
+        if (!overlay) {
+            goto exit;
+        }
+        if (base) {
+            ret = bdrv_change_backing_file(overlay, base->filename,
+                                           base->drv->format_name);
+        } else {
+            ret = bdrv_change_backing_file(overlay, NULL, NULL);
+        }
+        if (ret) {
+            goto exit;
+        }
+        if (base) {
+            drop_start = top->backing_hd;
+            bdrv_swap(top, base);
+            /* Break the loop formed by bdrv_swap */
+            bdrv_set_backing_hd(base, NULL);
+        } else {
+            bdrv_set_backing_hd(overlay, NULL);
+            drop_start = top;
         }
-        intermediate = intermediate->backing_hd;
-    }
-    if (base_bs == NULL) {
-        /* something went wrong, we did not end at the base. safely
-         * unravel everything, and exit with error */
-        goto exit;
-    }
-
-    /* success - we can delete the intermediate states, and link top->base */
-    ret = bdrv_change_backing_file(new_top_bs, base_bs->filename,
-                                   base_bs->drv ? base_bs->drv->format_name : "");
-    if (ret) {
-        goto exit;
-    }
-    new_top_bs->backing_hd = base_bs;
-
 
-    QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) {
-        /* so that bdrv_close() does not recursively close the chain */
-        intermediate_state->bs->backing_hd = NULL;
-        bdrv_unref(intermediate_state->bs);
+        bdrv_unref(drop_start);
     }
-    ret = 0;
-
 exit:
-    QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) {
-        g_free(intermediate_state);
-    }
     return ret;
 }
 
-
 static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
                                    size_t size)
 {
diff --git a/block/commit.c b/block/commit.c
index d4090cb..4d8cd05 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -142,6 +142,7 @@ wait:
     if (!block_job_is_cancelled(&s->common) && sector_num == end) {
         /* success */
         ret = bdrv_drop_intermediate(active, top, base);
+        base = top;
     }
 
 exit_free_buf:
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 09/11] stream: Use bdrv_drop_intermediate and drop close_unused_images

[Fam Zheng]

This reuses the new bdrv_drop_intermediate.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/stream.c | 28 +---------------------------
 1 file changed, 1 insertion(+), 27 deletions(-)

diff --git a/block/stream.c b/block/stream.c
index 46bec7d..9cdcf0e 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -51,32 +51,6 @@ static int coroutine_fn stream_populate(BlockDriverState *bs,
     return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov);
 }
 
-static void close_unused_images(BlockDriverState *top, BlockDriverState *base,
-                                const char *base_id)
-{
-    BlockDriverState *intermediate;
-    intermediate = top->backing_hd;
-
-    /* Must assign before bdrv_delete() to prevent traversing dangling pointer
-     * while we delete backing image instances.
-     */
-    top->backing_hd = base;
-
-    while (intermediate) {
-        BlockDriverState *unused;
-
-        /* reached base */
-        if (intermediate == base) {
-            break;
-        }
-
-        unused = intermediate;
-        intermediate = intermediate->backing_hd;
-        unused->backing_hd = NULL;
-        bdrv_unref(unused);
-    }
-}
-
 static void coroutine_fn stream_run(void *opaque)
 {
     StreamBlockJob *s = opaque;
@@ -190,7 +164,7 @@ wait:
             }
         }
         ret = bdrv_change_backing_file(bs, base_id, base_fmt);
-        close_unused_images(bs, base, base_id);
+        bdrv_drop_intermediate(bs, bs->backing_hd, base);
     }
 
     qemu_vfree(buf);
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 10/11] qmp: Add command 'blockdev-backup'

[Fam Zheng]

Similar to drive-backup, but this command uses a device id as target
instead of creating/opening an image file.

Also add blocker on target bs, since the target is also a named device
now.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/backup.c   | 21 +++++++++++++++++++++
 blockdev.c       | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 qapi-schema.json | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 qmp-commands.hx  | 44 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 161 insertions(+)

diff --git a/block/backup.c b/block/backup.c
index 0198514..c8fe1a9 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -339,6 +339,7 @@ static void coroutine_fn backup_run(void *opaque)
     hbitmap_free(job->bitmap);
 
     bdrv_iostatus_disable(target);
+    bdrv_op_unblock_all(target, job->common.blocker);
     bdrv_unref(target);
 
     block_job_completed(&job->common, ret);
@@ -364,6 +365,24 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
         return;
     }
 
+    if (!bdrv_is_inserted(bs)) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, bs->device_name);
+        return;
+    }
+
+    if (!bdrv_is_inserted(target)) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, target->device_name);
+        return;
+    }
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
+        return;
+    }
+
+    if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
+        return;
+    }
+
     len = bdrv_getlength(bs);
     if (len < 0) {
         error_setg_errno(errp, -len, "unable to get length for '%s'",
@@ -377,6 +396,8 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
         return;
     }
 
+    bdrv_op_block_all(target, job->common.blocker);
+
     job->on_source_error = on_source_error;
     job->on_target_error = on_target_error;
     job->target = target;
diff --git a/blockdev.c b/blockdev.c
index 7f305d8..5627e5d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1872,6 +1872,8 @@ void qmp_drive_backup(const char *device, const char *target,
         return;
     }
 
+    /* Although backup_run has this check too, we need to use bs->drv below, so
+     * do an early check redundantly. */
     if (!bdrv_is_inserted(bs)) {
         error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
         return;
@@ -1888,6 +1890,7 @@ void qmp_drive_backup(const char *device, const char *target,
         }
     }
 
+    /* Early check to avoid creating target */
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
         return;
     }
@@ -1946,6 +1949,50 @@ void qmp_drive_backup(const char *device, const char *target,
     }
 }
 
+void qmp_blockdev_backup(const char *device, const char *target,
+                         enum MirrorSyncMode sync,
+                         bool has_speed, int64_t speed,
+                         bool has_on_source_error,
+                         BlockdevOnError on_source_error,
+                         bool has_on_target_error,
+                         BlockdevOnError on_target_error,
+                         Error **errp)
+{
+    BlockDriverState *bs;
+    BlockDriverState *target_bs;
+    Error *local_err = NULL;
+
+    if (!has_speed) {
+        speed = 0;
+    }
+    if (!has_on_source_error) {
+        on_source_error = BLOCKDEV_ON_ERROR_REPORT;
+    }
+    if (!has_on_target_error) {
+        on_target_error = BLOCKDEV_ON_ERROR_REPORT;
+    }
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+
+    target_bs = bdrv_find(target);
+    if (!target_bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, target);
+        return;
+    }
+
+    bdrv_ref(target_bs);
+    backup_start(bs, target_bs, speed, sync, on_source_error, on_target_error,
+                 block_job_cb, bs, &local_err);
+    if (local_err != NULL) {
+        bdrv_unref(target_bs);
+        error_propagate(errp, local_err);
+    }
+}
+
 #define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
 
 void qmp_drive_mirror(const char *device, const char *target,
diff --git a/qapi-schema.json b/qapi-schema.json
index 288d024..e7c37c8 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1869,6 +1869,40 @@
             '*on-target-error': 'BlockdevOnError' } }
 
 ##
+# @BlockdevBackup
+#
+# @device: the name of the device which should be copied.
+#
+# @target: the name of the backup target device.
+#
+# @sync: what parts of the disk image should be copied to the destination
+#        (all the disk, only the sectors allocated in the topmost image, or
+#        only new I/O).
+#
+# @speed: #optional the maximum speed, in bytes per second.
+#
+# @on-source-error: #optional the action to take on an error on the source,
+#                   default 'report'.  'stop' and 'enospc' can only be used
+#                   if the block device supports io-status (see BlockInfo).
+#
+# @on-target-error: #optional the action to take on an error on the target,
+#                   default 'report' (no limitations, since this applies to
+#                   a different block device than @device).
+#
+# Note that @on-source-error and @on-target-error only affect background I/O.
+# If an error occurs during a guest write request, the device's rerror/werror
+# actions will be used.
+#
+# Since: 2.0
+##
+{ 'type': 'BlockdevBackup',
+  'data': { 'device': 'str', 'target': 'str',
+            'sync': 'MirrorSyncMode',
+            '*speed': 'int',
+            '*on-source-error': 'BlockdevOnError',
+            '*on-target-error': 'BlockdevOnError' } }
+
+##
 # @Abort
 #
 # This action can be used to test transaction failure.
@@ -2058,6 +2092,21 @@
 { 'command': 'drive-backup', 'data': 'DriveBackup' }
 
 ##
+# @blockdev-backup
+#
+# Block device version for drive-backup command. Use existing device as target
+# of backup.
+#
+# For the arguments, see the documentation of BlockdevBackup.
+#
+# Returns: Nothing on success.
+#          If @device or @target is not a valid block device, DeviceNotFound.
+#
+# Since 2.0
+##
+{ 'command': 'blockdev-backup', 'data': 'BlockdevBackup' }
+
+##
 # @drive-mirror
 #
 # Start mirroring a block device's writes to a new destination.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index fba15cd..32e2b10 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -963,6 +963,50 @@ Example:
                                                "sync": "full",
                                                "target": "backup.img" } }
 <- { "return": {} }
+
+EQMP
+
+    {
+        .name       = "blockdev-backup",
+        .args_type  = "sync:s,device:B,target:B,speed:i?,"
+                      "on-source-error:s?,on-target-error:s?",
+        .mhandler.cmd_new = qmp_marshal_input_blockdev_backup,
+    },
+
+SQMP
+blockdev-backup
+------------
+
+The device version of drive-backup: this command takes a existing named device
+as backup target.
+
+Arguments:
+
+- "device": the name of the device which should be copied.
+            (json-string)
+- "target": the target of the new image. If the file exists, or if it is a
+            device, the existing file/device will be used as the new
+            destination.  If it does not exist, a new file will be created.
+            (json-string)
+- "sync": what parts of the disk image should be copied to the destination;
+          possibilities include "full" for all the disk, "top" for only the
+          sectors allocated in the topmost image, or "none" to only replicate
+          new I/O (MirrorSyncMode).
+- "speed": the maximum speed, in bytes per second (json-int, optional)
+- "on-source-error": the action to take on an error on the source, default
+                     'report'.  'stop' and 'enospc' can only be used
+                     if the block device supports io-status.
+                     (BlockdevOnError, optional)
+- "on-target-error": the action to take on an error on the target, default
+                     'report' (no limitations, since this applies to
+                     a different block device than device).
+                     (BlockdevOnError, optional)
+
+Example:
+-> { "execute": "blockdev-backup", "arguments": { "device": "src-id",
+                                                  "target": "tgt-id" } }
+<- { "return": {} }
+
 EQMP
 
     {
-- 
1.8.5.1

[Qemu-devel] [PATCH v9 11/11] block: Allow backup on referenced named BlockDriverState

[Fam Zheng]

Drive backup is a read only operation on source bs. We want to allow
this specific case to enable image-fleecing. Note that when
image-fleecing job starts, the job still add its blocker to source bs,
and any other operation on it will be blocked by that.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block.c b/block.c
index b28fb93..1bc00ef 100644
--- a/block.c
+++ b/block.c
@@ -988,6 +988,8 @@ void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
     /* Otherwise we won't be able to commit due to check in bdrv_commit */
     bdrv_op_unblock(bs->backing_hd, BLOCK_OP_TYPE_COMMIT,
                     bs->backing_blocker);
+    bdrv_op_unblock(bs->backing_hd, BLOCK_OP_TYPE_BACKUP_SOURCE,
+                    bs->backing_blocker);
     pstrcpy(bs->backing_file, sizeof(bs->backing_file),
             bs->backing_hd->file->filename);
     pstrcpy(bs->backing_format, sizeof(bs->backing_format),
-- 
1.8.5.1