[Qemu-devel] [RFC 0/9] block: incremental backup transactions using BlockJobTxn

[Qemu-devel] [RFC 0/9] block: incremental backup transactions using BlockJobTxn

[Stefan Hajnoczi]

I stumbled on an idea for a simpler block job transactions implementation.
This series uses patches from John Snow's "[PATCH v6 00/10] block: incremental
backup transactions" series.  I wasn't sure if the idea would work, hence this
RFC instead of asking John to spend his time chasing the idea.

This series solves the problem at the blockjob level instead of in qmp
'transaction'.  This way no callbacks need to be intercepted and refcounts
don't need to be added to existing objects.

The advantage is this approach only requires small changes to blockdev.c and
block/backup.c.  The logic is encapsulated in the BlockJobTxn object, keeping
the transaction behavior isolated and easy to maintain.

Recap: motivation for block job transactions
--------------------------------------------
If an incremental backup block job fails then we reclaim the bitmap so
the job can be retried.  The problem comes when multiple jobs are started as
part of a qmp 'transaction' command.  We need to group these jobs in a
transaction so that either all jobs complete successfully or all bitmaps are
reclaimed.

Without transactions, there is a case where some jobs complete successfully and
throw away their bitmaps, making it impossible to retry the backup by rerunning
the command if one of the jobs fails.

How does this implementation work?
----------------------------------
These patches add a BlockJobTxn object with the following API:

  txn = block_job_txn_new();
  block_job_txn_add_job(txn, job1);
  block_job_txn_add_job(txn, job2);
  block_job_txn_begin();

The jobs either both complete successfully or they both fail/cancel.  If the
user cancels job1 then job2 will also be cancelled and vice versa.

Jobs stay alive waiting for other jobs to complete.  They can be cancelled by
the user during this time.  Job blockers are still in effect and no other block
job can run on this device in the meantime (since QEMU currently only allows 1
job per device).  This is the main drawback to this approach but reasonable
since you probably don't want to run other jobs/operations until you're sure
the backup was successful (you won't be able to retry a failed backup if
there's a new job running).

Adding transaction support to the backup job is very easy.  It just needs to
make a call before throwing away the bitmap and returning from its coroutine:

  block_job_txn_prepare_to_complete(job->txn, job, ret);

  if (job->sync_bitmap) {
      BdrvDirtyBitmap *bm;
      if (ret < 0 || block_job_is_cancelled(&job->common)) {
          ...

John Snow (4):
  qapi: Add transaction support to block-dirty-bitmap operations
  iotests: add transactional incremental backup test
  block: rename BlkTransactionState and BdrvActionOps
  iotests: 124 - transactional failure test

Kashyap Chamarthy (1):
  qmp-commands.hx: Update the supported 'transaction' operations

Stefan Hajnoczi (4):
  block: keep bitmap if incremental backup job is cancelled
  block: add block job transactions
  blockdev: make BlockJobTxn available to qmp 'transaction'
  block/backup: support block job transactions

 block.c                    |  19 ++-
 block/backup.c             |   9 +-
 blockdev.c                 | 298 +++++++++++++++++++++++++++++++++++----------
 blockjob.c                 | 160 ++++++++++++++++++++++++
 docs/bitmaps.md            |   6 +-
 include/block/block.h      |   2 +-
 include/block/block_int.h  |   6 +-
 include/block/blockjob.h   |  49 ++++++++
 qapi-schema.json           |   6 +-
 qmp-commands.hx            |  21 +++-
 tests/qemu-iotests/124     | 180 ++++++++++++++++++++++++++-
 tests/qemu-iotests/124.out |   4 +-
 trace-events               |   4 +
 13 files changed, 679 insertions(+), 85 deletions(-)

-- 
2.4.2

[Qemu-devel] [RFC 1/9] qapi: Add transaction support to block-dirty-bitmap operations

[Stefan Hajnoczi]

From: John Snow <jsnow@redhat.com>

This adds two qmp commands to transactions.

block-dirty-bitmap-add allows you to create a bitmap simultaneously
alongside a new full backup to accomplish a clean synchronization
point.

block-dirty-bitmap-clear allows you to reset a bitmap back to as-if
it were new, which can also be used alongside a full backup to
accomplish a clean synchronization point.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block.c                   |  19 +++++++-
 blockdev.c                | 114 +++++++++++++++++++++++++++++++++++++++++++++-
 docs/bitmaps.md           |   6 +--
 include/block/block.h     |   1 -
 include/block/block_int.h |   3 ++
 qapi-schema.json          |   6 ++-
 6 files changed, 139 insertions(+), 10 deletions(-)

diff --git a/block.c b/block.c
index 2b9ceae..a481654 100644
--- a/block.c
+++ b/block.c
@@ -3329,10 +3329,25 @@ void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
     hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
 }
 
-void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap)
+void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
-    hbitmap_reset(bitmap->bitmap, 0, bitmap->size);
+    if (!out) {
+        hbitmap_reset(bitmap->bitmap, 0, bitmap->size);
+    } else {
+        HBitmap *backup = bitmap->bitmap;
+        bitmap->bitmap = hbitmap_alloc(bitmap->size,
+                                       hbitmap_granularity(backup));
+        *out = backup;
+    }
+}
+
+void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *in)
+{
+    HBitmap *tmp = bitmap->bitmap;
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    bitmap->bitmap = in;
+    hbitmap_free(tmp);
 }
 
 void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
diff --git a/blockdev.c b/blockdev.c
index de94a8b..cc91270 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1694,6 +1694,106 @@ static void blockdev_backup_clean(BlkTransactionState *common)
     }
 }
 
+typedef struct BlockDirtyBitmapState {
+    BlkTransactionState common;
+    BdrvDirtyBitmap *bitmap;
+    BlockDriverState *bs;
+    AioContext *aio_context;
+    HBitmap *backup;
+    bool prepared;
+} BlockDirtyBitmapState;
+
+static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
+                                           Error **errp)
+{
+    Error *local_err = NULL;
+    BlockDirtyBitmapAdd *action;
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    action = common->action->block_dirty_bitmap_add;
+    /* AIO context taken and released within qmp_block_dirty_bitmap_add */
+    qmp_block_dirty_bitmap_add(action->node, action->name,
+                               action->has_granularity, action->granularity,
+                               &local_err);
+
+    if (!local_err) {
+        state->prepared = true;
+    } else {
+        error_propagate(errp, local_err);
+    }
+}
+
+static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
+{
+    BlockDirtyBitmapAdd *action;
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    action = common->action->block_dirty_bitmap_add;
+    /* Should not be able to fail: IF the bitmap was added via .prepare(),
+     * then the node reference and bitmap name must have been valid.
+     */
+    if (state->prepared) {
+        qmp_block_dirty_bitmap_remove(action->node, action->name, &error_abort);
+    }
+}
+
+static void block_dirty_bitmap_clear_prepare(BlkTransactionState *common,
+                                             Error **errp)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+    BlockDirtyBitmap *action;
+
+    action = common->action->block_dirty_bitmap_clear;
+    state->bitmap = block_dirty_bitmap_lookup(action->node,
+                                              action->name,
+                                              &state->bs,
+                                              &state->aio_context,
+                                              errp);
+    if (!state->bitmap) {
+        return;
+    }
+
+    if (bdrv_dirty_bitmap_frozen(state->bitmap)) {
+        error_setg(errp, "Cannot modify a frozen bitmap");
+        return;
+    } else if (!bdrv_dirty_bitmap_enabled(state->bitmap)) {
+        error_setg(errp, "Cannot clear a disabled bitmap");
+        return;
+    }
+
+    bdrv_clear_dirty_bitmap(state->bitmap, &state->backup);
+    /* AioContext is released in .clean() */
+}
+
+static void block_dirty_bitmap_clear_abort(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    bdrv_undo_clear_dirty_bitmap(state->bitmap, state->backup);
+}
+
+static void block_dirty_bitmap_clear_commit(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    hbitmap_free(state->backup);
+}
+
+static void block_dirty_bitmap_clear_clean(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    if (state->aio_context) {
+        aio_context_release(state->aio_context);
+    }
+}
+
 static void abort_prepare(BlkTransactionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
@@ -1734,6 +1834,18 @@ static const BdrvActionOps actions[] = {
         .abort = internal_snapshot_abort,
         .clean = internal_snapshot_clean,
     },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ADD] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_add_prepare,
+        .abort = block_dirty_bitmap_add_abort,
+    },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_CLEAR] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_clear_prepare,
+        .commit = block_dirty_bitmap_clear_commit,
+        .abort = block_dirty_bitmap_clear_abort,
+        .clean = block_dirty_bitmap_clear_clean,
+    }
 };
 
 /*
@@ -2107,7 +2219,7 @@ void qmp_block_dirty_bitmap_clear(const char *node, const char *name,
         goto out;
     }
 
-    bdrv_clear_dirty_bitmap(bitmap);
+    bdrv_clear_dirty_bitmap(bitmap, NULL);
 
  out:
     aio_context_release(aio_context);
diff --git a/docs/bitmaps.md b/docs/bitmaps.md
index f066b48..a60fee1 100644
--- a/docs/bitmaps.md
+++ b/docs/bitmaps.md
@@ -97,11 +97,7 @@ which is included at the end of this document.
 }
 ```
 
-## Transactions (Not yet implemented)
-
-* Transactional commands are forthcoming in a future version,
-  and are not yet available for use. This section serves as
-  documentation of intent for their design and usage.
+## Transactions
 
 ### Justification
 
diff --git a/include/block/block.h b/include/block/block.h
index f7680b6..3d62d3e 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -482,7 +482,6 @@ void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                            int64_t cur_sector, int nr_sectors);
 void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                              int64_t cur_sector, int nr_sectors);
-void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap);
 void bdrv_dirty_iter_init(BdrvDirtyBitmap *bitmap, struct HBitmapIter *hbi);
 void bdrv_set_dirty_iter(struct HBitmapIter *hbi, int64_t offset);
 int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f004378..5af712f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -641,4 +641,7 @@ void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
 void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector,
                       int nr_sectors);
 
+void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out);
+void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *in);
+
 #endif /* BLOCK_INT_H */
diff --git a/qapi-schema.json b/qapi-schema.json
index 6e17a5c..034eafb 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1490,6 +1490,8 @@
 # abort since 1.6
 # blockdev-snapshot-internal-sync since 1.7
 # blockdev-backup since 2.3
+# block-dirty-bitmap-add since 2.4
+# block-dirty-bitmap-clear since 2.4
 ##
 { 'union': 'TransactionAction',
   'data': {
@@ -1497,7 +1499,9 @@
        'drive-backup': 'DriveBackup',
        'blockdev-backup': 'BlockdevBackup',
        'abort': 'Abort',
-       'blockdev-snapshot-internal-sync': 'BlockdevSnapshotInternal'
+       'blockdev-snapshot-internal-sync': 'BlockdevSnapshotInternal',
+       'block-dirty-bitmap-add': 'BlockDirtyBitmapAdd',
+       'block-dirty-bitmap-clear': 'BlockDirtyBitmap'
    } }
 
 ##
-- 
2.4.2

[Qemu-devel] [RFC 2/9] iotests: add transactional incremental backup test

[Stefan Hajnoczi]

From: John Snow <jsnow@redhat.com>

Test simple usage cases for using transactions to create
and synchronize incremental backups.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/124     | 54 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/124.out |  4 ++--
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/tests/qemu-iotests/124 b/tests/qemu-iotests/124
index 3ee78cd..2d50594 100644
--- a/tests/qemu-iotests/124
+++ b/tests/qemu-iotests/124
@@ -36,6 +36,23 @@ def try_remove(img):
         pass
 
 
+def transaction_action(action, **kwargs):
+    return {
+        'type': action,
+        'data': kwargs
+    }
+
+
+def transaction_bitmap_clear(node, name, **kwargs):
+    return transaction_action('block-dirty-bitmap-clear',
+                              node=node, name=name, **kwargs)
+
+
+def transaction_drive_backup(device, target, **kwargs):
+    return transaction_action('drive-backup', device=device, target=target,
+                              **kwargs)
+
+
 class Bitmap:
     def __init__(self, name, drive):
         self.name = name
@@ -264,6 +281,43 @@ class TestIncrementalBackup(iotests.QMPTestCase):
         return self.do_incremental_simple(granularity=131072)
 
 
+    def test_incremental_transaction(self):
+        '''Test: Verify backups made from transactionally created bitmaps.
+
+        Create a bitmap "before" VM execution begins, then create a second
+        bitmap AFTER writes have already occurred. Use transactions to create
+        a full backup and synchronize both bitmaps to this backup.
+        Create an incremental backup through both bitmaps and verify that
+        both backups match the current drive0 image.
+        '''
+
+        drive0 = self.drives[0]
+        bitmap0 = self.add_bitmap('bitmap0', drive0)
+        self.hmp_io_writes(drive0['id'], (('0xab', 0, 512),
+                                          ('0xfe', '16M', '256k'),
+                                          ('0x64', '32736k', '64k')))
+        bitmap1 = self.add_bitmap('bitmap1', drive0)
+
+        result = self.vm.qmp('transaction', actions=[
+            transaction_bitmap_clear(bitmap0.drive['id'], bitmap0.name),
+            transaction_bitmap_clear(bitmap1.drive['id'], bitmap1.name),
+            transaction_drive_backup(drive0['id'], drive0['backup'],
+                                     sync='full', format=drive0['fmt'])
+        ])
+        self.assert_qmp(result, 'return', {})
+        self.wait_until_completed(drive0['id'])
+        self.files.append(drive0['backup'])
+
+        self.hmp_io_writes(drive0['id'], (('0x9a', 0, 512),
+                                          ('0x55', '8M', '352k'),
+                                          ('0x78', '15872k', '1M')))
+        # Both bitmaps should be correctly in sync.
+        self.create_incremental(bitmap0)
+        self.create_incremental(bitmap1)
+        self.vm.shutdown()
+        self.check_backups()
+
+
     def test_incremental_failure(self):
         '''Test: Verify backups made after a failure are correct.
 
diff --git a/tests/qemu-iotests/124.out b/tests/qemu-iotests/124.out
index 2f7d390..594c16f 100644
--- a/tests/qemu-iotests/124.out
+++ b/tests/qemu-iotests/124.out
@@ -1,5 +1,5 @@
-.......
+........
 ----------------------------------------------------------------------
-Ran 7 tests
+Ran 8 tests
 
 OK
-- 
2.4.2

[Qemu-devel] [RFC 3/9] block: rename BlkTransactionState and BdrvActionOps

[Stefan Hajnoczi]

From: John Snow <jsnow@redhat.com>

These structures are misnomers, somewhat.

(1) BlockTransactionState is not state for a transaction,
    but is rather state for a single transaction action.
    Rename it "BlkActionState" to be more accurate.

(2) The BdrvActionOps describes operations for the BlkActionState,
    above. This name might imply a 'BdrvAction' or a 'BdrvActionState',
    which there isn't.
    Rename this to 'BlkActionOps' to match 'BlkActionState'.

Lastly, update the surrounding in-line documentation and comments
to reflect the current nature of how Transactions operate.

This patch changes only comments and names, and should not affect
behavior in any way.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 blockdev.c | 116 ++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 65 insertions(+), 51 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index cc91270..e30e986 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1228,43 +1228,57 @@ static BdrvDirtyBitmap *block_dirty_bitmap_lookup(const char *node,
 
 /* New and old BlockDriverState structs for atomic group operations */
 
-typedef struct BlkTransactionState BlkTransactionState;
+typedef struct BlkActionState BlkActionState;
 
-/* Only prepare() may fail. In a single transaction, only one of commit() or
-   abort() will be called, clean() will always be called if it present. */
-typedef struct BdrvActionOps {
-    /* Size of state struct, in bytes. */
+/**
+ * BlkActionOps:
+ * Table of operations that define an Action.
+ *
+ * @instance_size: Size of state struct, in bytes.
+ * @prepare: Prepare the work, must NOT be NULL.
+ * @commit: Commit the changes, can be NULL.
+ * @abort: Abort the changes on fail, can be NULL.
+ * @clean: Clean up resources after all transaction actions have called
+ *         commit() or abort(). Can be NULL.
+ *
+ * Only prepare() may fail. In a single transaction, only one of commit() or
+ * abort() will be called. clean() will always be called if it is present.
+ */
+typedef struct BlkActionOps {
     size_t instance_size;
-    /* Prepare the work, must NOT be NULL. */
-    void (*prepare)(BlkTransactionState *common, Error **errp);
-    /* Commit the changes, can be NULL. */
-    void (*commit)(BlkTransactionState *common);
-    /* Abort the changes on fail, can be NULL. */
-    void (*abort)(BlkTransactionState *common);
-    /* Clean up resource in the end, can be NULL. */
-    void (*clean)(BlkTransactionState *common);
-} BdrvActionOps;
+    void (*prepare)(BlkActionState *common, Error **errp);
+    void (*commit)(BlkActionState *common);
+    void (*abort)(BlkActionState *common);
+    void (*clean)(BlkActionState *common);
+} BlkActionOps;
 
-/*
- * This structure must be arranged as first member in child type, assuming
- * that compiler will also arrange it to the same address with parent instance.
- * Later it will be used in free().
+/**
+ * BlkActionState:
+ * Describes one Action's state within a Transaction.
+ *
+ * @action: QAPI-defined enum identifying which Action to perform.
+ * @ops: Table of ActionOps this Action can perform.
+ * @entry: List membership for all Actions in this Transaction.
+ *
+ * This structure must be arranged as first member in a subclassed type,
+ * assuming that the compiler will also arrange it to the same offsets as the
+ * base class.
  */
-struct BlkTransactionState {
+struct BlkActionState {
     TransactionAction *action;
-    const BdrvActionOps *ops;
-    QSIMPLEQ_ENTRY(BlkTransactionState) entry;
+    const BlkActionOps *ops;
+    QSIMPLEQ_ENTRY(BlkActionState) entry;
 };
 
 /* internal snapshot private data */
 typedef struct InternalSnapshotState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *bs;
     AioContext *aio_context;
     QEMUSnapshotInfo sn;
 } InternalSnapshotState;
 
-static void internal_snapshot_prepare(BlkTransactionState *common,
+static void internal_snapshot_prepare(BlkActionState *common,
                                       Error **errp)
 {
     Error *local_err = NULL;
@@ -1359,7 +1373,7 @@ static void internal_snapshot_prepare(BlkTransactionState *common,
     state->bs = bs;
 }
 
-static void internal_snapshot_abort(BlkTransactionState *common)
+static void internal_snapshot_abort(BlkActionState *common)
 {
     InternalSnapshotState *state =
                              DO_UPCAST(InternalSnapshotState, common, common);
@@ -1382,7 +1396,7 @@ static void internal_snapshot_abort(BlkTransactionState *common)
     }
 }
 
-static void internal_snapshot_clean(BlkTransactionState *common)
+static void internal_snapshot_clean(BlkActionState *common)
 {
     InternalSnapshotState *state = DO_UPCAST(InternalSnapshotState,
                                              common, common);
@@ -1394,13 +1408,13 @@ static void internal_snapshot_clean(BlkTransactionState *common)
 
 /* external snapshot private data */
 typedef struct ExternalSnapshotState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *old_bs;
     BlockDriverState *new_bs;
     AioContext *aio_context;
 } ExternalSnapshotState;
 
-static void external_snapshot_prepare(BlkTransactionState *common,
+static void external_snapshot_prepare(BlkActionState *common,
                                       Error **errp)
 {
     BlockDriver *drv;
@@ -1521,7 +1535,7 @@ static void external_snapshot_prepare(BlkTransactionState *common,
     }
 }
 
-static void external_snapshot_commit(BlkTransactionState *common)
+static void external_snapshot_commit(BlkActionState *common)
 {
     ExternalSnapshotState *state =
                              DO_UPCAST(ExternalSnapshotState, common, common);
@@ -1539,7 +1553,7 @@ static void external_snapshot_commit(BlkTransactionState *common)
     aio_context_release(state->aio_context);
 }
 
-static void external_snapshot_abort(BlkTransactionState *common)
+static void external_snapshot_abort(BlkActionState *common)
 {
     ExternalSnapshotState *state =
                              DO_UPCAST(ExternalSnapshotState, common, common);
@@ -1552,13 +1566,13 @@ static void external_snapshot_abort(BlkTransactionState *common)
 }
 
 typedef struct DriveBackupState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *bs;
     AioContext *aio_context;
     BlockJob *job;
 } DriveBackupState;
 
-static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
+static void drive_backup_prepare(BlkActionState *common, Error **errp)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
     BlockDriverState *bs;
@@ -1598,7 +1612,7 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
     state->job = state->bs->job;
 }
 
-static void drive_backup_abort(BlkTransactionState *common)
+static void drive_backup_abort(BlkActionState *common)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
     BlockDriverState *bs = state->bs;
@@ -1609,7 +1623,7 @@ static void drive_backup_abort(BlkTransactionState *common)
     }
 }
 
-static void drive_backup_clean(BlkTransactionState *common)
+static void drive_backup_clean(BlkActionState *common)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
 
@@ -1619,13 +1633,13 @@ static void drive_backup_clean(BlkTransactionState *common)
 }
 
 typedef struct BlockdevBackupState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *bs;
     BlockJob *job;
     AioContext *aio_context;
 } BlockdevBackupState;
 
-static void blockdev_backup_prepare(BlkTransactionState *common, Error **errp)
+static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
     BlockdevBackup *backup;
@@ -1674,7 +1688,7 @@ static void blockdev_backup_prepare(BlkTransactionState *common, Error **errp)
     state->job = state->bs->job;
 }
 
-static void blockdev_backup_abort(BlkTransactionState *common)
+static void blockdev_backup_abort(BlkActionState *common)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
     BlockDriverState *bs = state->bs;
@@ -1685,7 +1699,7 @@ static void blockdev_backup_abort(BlkTransactionState *common)
     }
 }
 
-static void blockdev_backup_clean(BlkTransactionState *common)
+static void blockdev_backup_clean(BlkActionState *common)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
 
@@ -1695,7 +1709,7 @@ static void blockdev_backup_clean(BlkTransactionState *common)
 }
 
 typedef struct BlockDirtyBitmapState {
-    BlkTransactionState common;
+    BlkActionState common;
     BdrvDirtyBitmap *bitmap;
     BlockDriverState *bs;
     AioContext *aio_context;
@@ -1703,7 +1717,7 @@ typedef struct BlockDirtyBitmapState {
     bool prepared;
 } BlockDirtyBitmapState;
 
-static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
+static void block_dirty_bitmap_add_prepare(BlkActionState *common,
                                            Error **errp)
 {
     Error *local_err = NULL;
@@ -1724,7 +1738,7 @@ static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
     }
 }
 
-static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
+static void block_dirty_bitmap_add_abort(BlkActionState *common)
 {
     BlockDirtyBitmapAdd *action;
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
@@ -1739,7 +1753,7 @@ static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
     }
 }
 
-static void block_dirty_bitmap_clear_prepare(BlkTransactionState *common,
+static void block_dirty_bitmap_clear_prepare(BlkActionState *common,
                                              Error **errp)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
@@ -1768,7 +1782,7 @@ static void block_dirty_bitmap_clear_prepare(BlkTransactionState *common,
     /* AioContext is released in .clean() */
 }
 
-static void block_dirty_bitmap_clear_abort(BlkTransactionState *common)
+static void block_dirty_bitmap_clear_abort(BlkActionState *common)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
@@ -1776,7 +1790,7 @@ static void block_dirty_bitmap_clear_abort(BlkTransactionState *common)
     bdrv_undo_clear_dirty_bitmap(state->bitmap, state->backup);
 }
 
-static void block_dirty_bitmap_clear_commit(BlkTransactionState *common)
+static void block_dirty_bitmap_clear_commit(BlkActionState *common)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
@@ -1784,7 +1798,7 @@ static void block_dirty_bitmap_clear_commit(BlkTransactionState *common)
     hbitmap_free(state->backup);
 }
 
-static void block_dirty_bitmap_clear_clean(BlkTransactionState *common)
+static void block_dirty_bitmap_clear_clean(BlkActionState *common)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
@@ -1794,17 +1808,17 @@ static void block_dirty_bitmap_clear_clean(BlkTransactionState *common)
     }
 }
 
-static void abort_prepare(BlkTransactionState *common, Error **errp)
+static void abort_prepare(BlkActionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
 }
 
-static void abort_commit(BlkTransactionState *common)
+static void abort_commit(BlkActionState *common)
 {
     g_assert_not_reached(); /* this action never succeeds */
 }
 
-static const BdrvActionOps actions[] = {
+static const BlkActionOps actions[] = {
     [TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC] = {
         .instance_size = sizeof(ExternalSnapshotState),
         .prepare  = external_snapshot_prepare,
@@ -1824,7 +1838,7 @@ static const BdrvActionOps actions[] = {
         .clean = blockdev_backup_clean,
     },
     [TRANSACTION_ACTION_KIND_ABORT] = {
-        .instance_size = sizeof(BlkTransactionState),
+        .instance_size = sizeof(BlkActionState),
         .prepare = abort_prepare,
         .commit = abort_commit,
     },
@@ -1855,10 +1869,10 @@ static const BdrvActionOps actions[] = {
 void qmp_transaction(TransactionActionList *dev_list, Error **errp)
 {
     TransactionActionList *dev_entry = dev_list;
-    BlkTransactionState *state, *next;
+    BlkActionState *state, *next;
     Error *local_err = NULL;
 
-    QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionState) snap_bdrv_states;
+    QSIMPLEQ_HEAD(snap_bdrv_states, BlkActionState) snap_bdrv_states;
     QSIMPLEQ_INIT(&snap_bdrv_states);
 
     /* drain all i/o before any operations */
@@ -1867,7 +1881,7 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
     /* We don't do anything in this loop that commits us to the operations */
     while (NULL != dev_entry) {
         TransactionAction *dev_info = NULL;
-        const BdrvActionOps *ops;
+        const BlkActionOps *ops;
 
         dev_info = dev_entry->value;
         dev_entry = dev_entry->next;
-- 
2.4.2

[Qemu-devel] [RFC 4/9] block: keep bitmap if incremental backup job is cancelled

[Stefan Hajnoczi]

Reclaim the dirty bitmap if an incremental backup block job is
cancelled.  The ret variable may be 0 when the job is cancelled so it's
not enough to check ret < 0.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/backup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/backup.c b/block/backup.c
index d3f648d..c1ad975 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -430,7 +430,7 @@ static void coroutine_fn backup_run(void *opaque)
 
     if (job->sync_bitmap) {
         BdrvDirtyBitmap *bm;
-        if (ret < 0) {
+        if (ret < 0 || block_job_is_cancelled(&job->common)) {
             /* Merge the successor back into the parent, delete nothing. */
             bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
             assert(bm);
-- 
2.4.2

[Qemu-devel] [RFC 5/9] block: add block job transactions

[Stefan Hajnoczi]

Sometimes block jobs must execute as a transaction group.  Finishing
jobs wait until all other jobs are ready to complete successfully.
Failure or cancellation of one job cancels the other jobs in the group.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 blockjob.c                | 160 ++++++++++++++++++++++++++++++++++++++++++++++
 include/block/block.h     |   1 +
 include/block/block_int.h |   3 +-
 include/block/blockjob.h  |  49 ++++++++++++++
 trace-events              |   4 ++
 5 files changed, 216 insertions(+), 1 deletion(-)

diff --git a/blockjob.c b/blockjob.c
index 2755465..ff622f5 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -399,3 +399,163 @@ void block_job_defer_to_main_loop(BlockJob *job,
 
     qemu_bh_schedule(data->bh);
 }
+
+/* Transactional group of block jobs */
+struct BlockJobTxn {
+    /* Jobs may be in different AioContexts so protect all fields */
+    QemuMutex lock;
+
+    /* Reference count for txn object */
+    unsigned int ref;
+
+    /* Is this txn cancelling its jobs? */
+    bool aborting;
+
+    /* Number of jobs still running */
+    unsigned int jobs_pending;
+
+    /* List of jobs */
+    QLIST_HEAD(, BlockJob) jobs;
+};
+
+BlockJobTxn *block_job_txn_new(void)
+{
+    BlockJobTxn *txn = g_new(BlockJobTxn, 1);
+    qemu_mutex_init(&txn->lock);
+    txn->ref = 1; /* dropped by block_job_txn_begin() */
+    txn->aborting = false;
+    txn->jobs_pending = 0;
+    QLIST_INIT(&txn->jobs);
+    return txn;
+}
+
+static void block_job_txn_unref(BlockJobTxn *txn)
+{
+    qemu_mutex_lock(&txn->lock);
+
+    if (--txn->ref > 0) {
+        qemu_mutex_unlock(&txn->lock);
+        return;
+    }
+
+    qemu_mutex_unlock(&txn->lock);
+    qemu_mutex_destroy(&txn->lock);
+    g_free(txn);
+}
+
+/* The purpose of this is to keep txn alive until all jobs have been added */
+void block_job_txn_begin(BlockJobTxn *txn)
+{
+    block_job_txn_unref(txn);
+}
+
+void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
+{
+    if (!txn) {
+        return;
+    }
+
+    assert(!job->txn);
+    job->txn = txn;
+
+    qemu_mutex_lock(&txn->lock);
+    txn->ref++;
+    txn->jobs_pending++;
+    QLIST_INSERT_HEAD(&txn->jobs, job, txn_list);
+    qemu_mutex_unlock(&txn->lock);
+}
+
+/* Cancel all other jobs in case of abort, wake all waiting jobs in case of
+ * successful completion.  Runs from main loop.
+ */
+static void block_job_txn_complete(BlockJob *job, void *opaque)
+{
+    BlockJobTxn *txn = opaque;
+    BlockJob *other_job;
+    bool aborting = txn->aborting;
+
+    qemu_mutex_lock(&txn->lock);
+    txn->ref++; /* keep txn alive until the end of this loop */
+
+    QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
+        AioContext *ctx;
+
+        qemu_mutex_unlock(&txn->lock);
+        ctx = bdrv_get_aio_context(other_job->bs);
+        aio_context_acquire(ctx);
+
+        /* Cancel all other jobs if aborting.  Don't cancel our own failed job
+         * since cancellation throws away the error value.
+         */
+        if (aborting && other_job != job) {
+            block_job_cancel(other_job);
+        } else {
+            block_job_enter(other_job);
+        }
+
+        aio_context_release(ctx);
+        qemu_mutex_lock(&txn->lock);
+    }
+
+    qemu_mutex_unlock(&txn->lock);
+    block_job_txn_unref(txn);
+}
+
+void coroutine_fn block_job_txn_prepare_to_complete(BlockJobTxn *txn,
+                                                    BlockJob *job,
+                                                    int ret)
+{
+    if (!txn) {
+        return;
+    }
+
+    qemu_mutex_lock(&txn->lock);
+
+    /* This function is entered in 3 cases:
+     *
+     * 1. Successful job completion - wait for other jobs
+     * 2. First failed/cancelled job in txn - cancel other jobs and wait
+     * 3. Subsequent cancelled jobs - finish immediately, don't wait
+     */
+    trace_block_job_txn_prepare_to_complete_entry(txn, job, ret,
+                                                  block_job_is_cancelled(job),
+                                                  txn->aborting,
+                                                  txn->jobs_pending);
+
+    if (txn->aborting) { /* Case 3 */
+        assert(block_job_is_cancelled(job));
+        goto out; /* already cancelled, don't yield */
+    }
+
+    if (ret != 0 || block_job_is_cancelled(job)) { /* Case 2 */
+abort:
+        txn->aborting = true;
+        block_job_defer_to_main_loop(job, block_job_txn_complete, txn);
+    } else { /* Case 1 */
+        if (--txn->jobs_pending == 0) {
+            block_job_defer_to_main_loop(job, block_job_txn_complete, txn);
+        }
+    }
+
+    /* Wait for block_job_txn_complete() */
+    do {
+        qemu_mutex_unlock(&txn->lock);
+        job->busy = false;
+        qemu_coroutine_yield();
+        job->busy = true;
+        qemu_mutex_lock(&txn->lock);
+
+        if (block_job_is_cancelled(job) && !txn->aborting) {
+            goto abort; /* this job just got cancelled by the user */
+        }
+    } while (!txn->aborting && txn->jobs_pending > 0);
+
+out:
+    trace_block_job_txn_prepare_to_complete_return(txn, job, ret,
+                                                   block_job_is_cancelled(job),
+                                                   txn->aborting,
+                                                   txn->jobs_pending);
+
+    qemu_mutex_unlock(&txn->lock);
+    block_job_txn_unref(txn);
+}
diff --git a/include/block/block.h b/include/block/block.h
index 3d62d3e..439925c 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -12,6 +12,7 @@
 /* block.c */
 typedef struct BlockDriver BlockDriver;
 typedef struct BlockJob BlockJob;
+typedef struct BlockJobTxn BlockJobTxn;
 
 typedef struct BlockDriverInfo {
     /* in bytes, 0 if irrelevant */
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 5af712f..9464142 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -617,6 +617,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
  * @on_source_error: The action to take upon error reading from the source.
  * @on_target_error: The action to take upon error writing to the target.
  * @cb: Completion function for the job.
+ * @txn: Transaction that this job is part of (may be NULL).
  * @opaque: Opaque pointer value passed to @cb.
  *
  * Start a backup operation on @bs.  Clusters in @bs are written to @target
@@ -628,7 +629,7 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
                   BlockCompletionFunc *cb, void *opaque,
-                  Error **errp);
+                  BlockJobTxn *txn, Error **errp);
 
 void blk_dev_change_media_cb(BlockBackend *blk, bool load);
 bool blk_dev_has_removable_media(BlockBackend *blk);
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 57d8ef1..ce57e98 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -122,6 +122,10 @@ struct BlockJob {
 
     /** The opaque value that is passed to the completion function.  */
     void *opaque;
+
+    /** Non-NULL if this job is part of a transaction */
+    BlockJobTxn *txn;
+    QLIST_ENTRY(BlockJob) txn_list;
 };
 
 /**
@@ -348,4 +352,49 @@ void block_job_defer_to_main_loop(BlockJob *job,
                                   BlockJobDeferToMainLoopFn *fn,
                                   void *opaque);
 
+/**
+ * block_job_txn_new:
+ *
+ * Allocate and return a new block job transaction.  Jobs can be added to the
+ * transaction using block_job_txn_add_job().  block_job_txn_begin() must be
+ * called when all jobs (if any) have been added.
+ *
+ * All jobs in the transaction either complete successfully or fail/cancel as a
+ * group.  Jobs wait for each other before completing.  Cancelling one job
+ * cancels all jobs in the transaction.
+ */
+BlockJobTxn *block_job_txn_new(void);
+
+/**
+ * block_job_txn_add_job:
+ * @txn: The transaction
+ * @job: Job to add to the transaction
+ *
+ * Add @job to the transaction.  The @job must not already be in a transaction.
+ * The block job driver must call block_job_txn_prepare_to_complete() before
+ * final cleanup and completion.
+ */
+void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job);
+
+/**
+ * block_job_txn_begin:
+ * @txn: The transaction
+ *
+ * Call this to mark the end of adding jobs to the transaction.  This must be
+ * called even if no jobs were added.
+ */
+void block_job_txn_begin(BlockJobTxn *txn);
+
+/**
+ * block_job_txn_prepare_to_complete:
+ * @txn: The transaction
+ * @job: The block job
+ * @ret: Block job return value (0 for success, otherwise job failure)
+ *
+ * Wait for other jobs in the transaction to complete.  If @ret is non-zero or
+ * @job is cancelled, all other jobs in the transaction will be cancelled.
+ */
+void coroutine_fn block_job_txn_prepare_to_complete(BlockJobTxn *txn,
+                                                    BlockJob *job, int ret);
+
 #endif
diff --git a/trace-events b/trace-events
index a589650..526e6ac 100644
--- a/trace-events
+++ b/trace-events
@@ -123,6 +123,10 @@ virtio_blk_data_plane_start(void *s) "dataplane %p"
 virtio_blk_data_plane_stop(void *s) "dataplane %p"
 virtio_blk_data_plane_process_request(void *s, unsigned int out_num, unsigned int in_num, unsigned int head) "dataplane %p out_num %u in_num %u head %u"
 
+# blockjob.c
+block_job_txn_prepare_to_complete_entry(void *txn, void *job, int ret, bool cancelled, bool aborting, unsigned int jobs_pending) "txn %p job %p ret %d cancelled %d aborting %d jobs_pending %u"
+block_job_txn_prepare_to_complete_return(void *txn, void *job, int ret, bool cancelled, bool aborting, unsigned int jobs_pending) "txn %p job %p ret %d cancelled %d aborting %d jobs_pending %u"
+
 # hw/virtio/dataplane/vring.c
 vring_setup(uint64_t physical, void *desc, void *avail, void *used) "vring physical %#"PRIx64" desc %p avail %p used %p"
 
-- 
2.4.2

[Qemu-devel] [RFC 6/9] blockdev: make BlockJobTxn available to qmp 'transaction'

[Stefan Hajnoczi]

Provide a BlockJobTxn to actions executed in a qmp 'transaction'
command.  This allows actions to make their block jobs either complete
as a group or fail/cancel together.

The next patch adds the first user.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 blockdev.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index e30e986..2cdc7f3 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1267,6 +1267,7 @@ typedef struct BlkActionOps {
 struct BlkActionState {
     TransactionAction *action;
     const BlkActionOps *ops;
+    BlockJobTxn *block_job_txn;
     QSIMPLEQ_ENTRY(BlkActionState) entry;
 };
 
@@ -1869,12 +1870,15 @@ static const BlkActionOps actions[] = {
 void qmp_transaction(TransactionActionList *dev_list, Error **errp)
 {
     TransactionActionList *dev_entry = dev_list;
+    BlockJobTxn *block_job_txn;
     BlkActionState *state, *next;
     Error *local_err = NULL;
 
     QSIMPLEQ_HEAD(snap_bdrv_states, BlkActionState) snap_bdrv_states;
     QSIMPLEQ_INIT(&snap_bdrv_states);
 
+    block_job_txn = block_job_txn_new();
+
     /* drain all i/o before any operations */
     bdrv_drain_all();
 
@@ -1894,6 +1898,7 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
         state = g_malloc0(ops->instance_size);
         state->ops = ops;
         state->action = dev_info;
+        state->block_job_txn = block_job_txn;
         QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, state, entry);
 
         state->ops->prepare(state, &local_err);
@@ -1903,6 +1908,8 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
         }
     }
 
+    block_job_txn_begin(block_job_txn);
+
     QSIMPLEQ_FOREACH(state, &snap_bdrv_states, entry) {
         if (state->ops->commit) {
             state->ops->commit(state);
@@ -1913,6 +1920,8 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
     goto exit;
 
 delete_and_fail:
+    block_job_txn_begin(block_job_txn);
+
     /* failure, and it is all-or-none; roll back all operations */
     QSIMPLEQ_FOREACH(state, &snap_bdrv_states, entry) {
         if (state->ops->abort) {
-- 
2.4.2

[Qemu-devel] [RFC 7/9] block/backup: support block job transactions

[Stefan Hajnoczi]

Join the transaction when the backup block job is in incremental backup
mode.

This ensures that the sync bitmap is not thrown away if another block
job in the transaction is cancelled or fails.  This is critical so
incremental backup with multiple disks can be retried in case of
cancellation/failure.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/backup.c |  7 +++++-
 blockdev.c     | 73 ++++++++++++++++++++++++++++++++++++++++++----------------
 2 files changed, 59 insertions(+), 21 deletions(-)

diff --git a/block/backup.c b/block/backup.c
index c1ad975..ecc1b00 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -428,6 +428,8 @@ static void coroutine_fn backup_run(void *opaque)
     qemu_co_rwlock_wrlock(&job->flush_rwlock);
     qemu_co_rwlock_unlock(&job->flush_rwlock);
 
+    block_job_txn_prepare_to_complete(job->common.txn, &job->common, ret);
+
     if (job->sync_bitmap) {
         BdrvDirtyBitmap *bm;
         if (ret < 0 || block_job_is_cancelled(&job->common)) {
@@ -456,7 +458,7 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
                   BlockCompletionFunc *cb, void *opaque,
-                  Error **errp)
+                  BlockJobTxn *txn, Error **errp)
 {
     int64_t len;
 
@@ -536,6 +538,9 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
     job->sync_mode = sync_mode;
     job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_DIRTY_BITMAP ?
                        sync_bitmap : NULL;
+    if (job->sync_bitmap) {
+        block_job_txn_add_job(txn, &job->common);
+    }
     job->common.len = len;
     job->common.co = qemu_coroutine_create(backup_run);
     qemu_coroutine_enter(job->common.co, job);
diff --git a/blockdev.c b/blockdev.c
index 2cdc7f3..aa46d7c 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1573,6 +1573,18 @@ typedef struct DriveBackupState {
     BlockJob *job;
 } DriveBackupState;
 
+static void do_drive_backup(const char *device, const char *target,
+                            bool has_format, const char *format,
+                            enum MirrorSyncMode sync,
+                            bool has_mode, enum NewImageMode mode,
+                            bool has_speed, int64_t speed,
+                            bool has_bitmap, const char *bitmap,
+                            bool has_on_source_error,
+                            BlockdevOnError on_source_error,
+                            bool has_on_target_error,
+                            BlockdevOnError on_target_error,
+                            BlockJobTxn *txn, Error **errp);
+
 static void drive_backup_prepare(BlkActionState *common, Error **errp)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
@@ -1595,15 +1607,16 @@ static void drive_backup_prepare(BlkActionState *common, Error **errp)
     state->aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(state->aio_context);
 
-    qmp_drive_backup(backup->device, backup->target,
-                     backup->has_format, backup->format,
-                     backup->sync,
-                     backup->has_mode, backup->mode,
-                     backup->has_speed, backup->speed,
-                     backup->has_bitmap, backup->bitmap,
-                     backup->has_on_source_error, backup->on_source_error,
-                     backup->has_on_target_error, backup->on_target_error,
-                     &local_err);
+    do_drive_backup(backup->device, backup->target,
+                    backup->has_format, backup->format,
+                    backup->sync,
+                    backup->has_mode, backup->mode,
+                    backup->has_speed, backup->speed,
+                    backup->has_bitmap, backup->bitmap,
+                    backup->has_on_source_error, backup->on_source_error,
+                    backup->has_on_target_error, backup->on_target_error,
+                    common->block_job_txn,
+                    &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         return;
@@ -2559,15 +2572,17 @@ out:
     aio_context_release(aio_context);
 }
 
-void qmp_drive_backup(const char *device, const char *target,
-                      bool has_format, const char *format,
-                      enum MirrorSyncMode sync,
-                      bool has_mode, enum NewImageMode mode,
-                      bool has_speed, int64_t speed,
-                      bool has_bitmap, const char *bitmap,
-                      bool has_on_source_error, BlockdevOnError on_source_error,
-                      bool has_on_target_error, BlockdevOnError on_target_error,
-                      Error **errp)
+static void do_drive_backup(const char *device, const char *target,
+                            bool has_format, const char *format,
+                            enum MirrorSyncMode sync,
+                            bool has_mode, enum NewImageMode mode,
+                            bool has_speed, int64_t speed,
+                            bool has_bitmap, const char *bitmap,
+                            bool has_on_source_error,
+                            BlockdevOnError on_source_error,
+                            bool has_on_target_error,
+                            BlockdevOnError on_target_error,
+                            BlockJobTxn *txn, Error **errp)
 {
     BlockBackend *blk;
     BlockDriverState *bs;
@@ -2683,7 +2698,7 @@ void qmp_drive_backup(const char *device, const char *target,
 
     backup_start(bs, target_bs, speed, sync, bmap,
                  on_source_error, on_target_error,
-                 block_job_cb, bs, &local_err);
+                 block_job_cb, bs, txn, &local_err);
     if (local_err != NULL) {
         bdrv_unref(target_bs);
         error_propagate(errp, local_err);
@@ -2694,6 +2709,24 @@ out:
     aio_context_release(aio_context);
 }
 
+void qmp_drive_backup(const char *device, const char *target,
+                      bool has_format, const char *format,
+                      enum MirrorSyncMode sync,
+                      bool has_mode, enum NewImageMode mode,
+                      bool has_speed, int64_t speed,
+                      bool has_bitmap, const char *bitmap,
+                      bool has_on_source_error, BlockdevOnError on_source_error,
+                      bool has_on_target_error, BlockdevOnError on_target_error,
+                      Error **errp)
+{
+    return do_drive_backup(device, target, has_format, format, sync,
+                           has_mode, mode, has_speed, speed,
+                           has_bitmap, bitmap,
+                           has_on_source_error, on_source_error,
+                           has_on_target_error, on_target_error,
+                           NULL, errp);
+}
+
 BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
 {
     return bdrv_named_nodes_list(errp);
@@ -2744,7 +2777,7 @@ void qmp_blockdev_backup(const char *device, const char *target,
     bdrv_ref(target_bs);
     bdrv_set_aio_context(target_bs, aio_context);
     backup_start(bs, target_bs, speed, sync, NULL, on_source_error,
-                 on_target_error, block_job_cb, bs, &local_err);
+                 on_target_error, block_job_cb, bs, NULL, &local_err);
     if (local_err != NULL) {
         bdrv_unref(target_bs);
         error_propagate(errp, local_err);
-- 
2.4.2

[Qemu-devel] [RFC 8/9] iotests: 124 - transactional failure test

[Stefan Hajnoczi]

From: John Snow <jsnow@redhat.com>

Use a transaction to request an incremental backup across two drives.
Coerce one of the jobs to fail, and then re-run the transaction.

Verify that no bitmap data was lost due to the partial transaction
failure.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/124     | 126 ++++++++++++++++++++++++++++++++++++++++++++-
 tests/qemu-iotests/124.out |   4 +-
 2 files changed, 127 insertions(+), 3 deletions(-)

diff --git a/tests/qemu-iotests/124 b/tests/qemu-iotests/124
index 2d50594..ea820a0 100644
--- a/tests/qemu-iotests/124
+++ b/tests/qemu-iotests/124
@@ -139,9 +139,12 @@ class TestIncrementalBackup(iotests.QMPTestCase):
     def do_qmp_backup(self, error='Input/output error', **kwargs):
         res = self.vm.qmp('drive-backup', **kwargs)
         self.assert_qmp(res, 'return', {})
+        return self.wait_qmp_backup(kwargs['device'], error)
 
+
+    def wait_qmp_backup(self, device, error='Input/output error'):
         event = self.vm.event_wait(name="BLOCK_JOB_COMPLETED",
-                                   match={'data': {'device': kwargs['device']}})
+                                   match={'data': {'device': device}})
         self.assertIsNotNone(event)
 
         try:
@@ -156,6 +159,12 @@ class TestIncrementalBackup(iotests.QMPTestCase):
             return False
 
 
+    def wait_qmp_backup_cancelled(self, device):
+        event = self.vm.event_wait(name='BLOCK_JOB_CANCELLED',
+                                   match={'data': {'device': device}})
+        self.assertIsNotNone(event)
+
+
     def create_anchor_backup(self, drive=None):
         if drive is None:
             drive = self.drives[-1]
@@ -375,6 +384,121 @@ class TestIncrementalBackup(iotests.QMPTestCase):
         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.
+        '''
+
+        # Create a second drive, with pattern:
+        drive1 = self.add_node('drive1')
+        self.img_create(drive1['file'], drive1['fmt'])
+        io_write_patterns(drive1['file'], (('0x14', 0, 512),
+                                           ('0x5d', '1M', '32k'),
+                                           ('0xcd', '32M', '124k')))
+
+        # Create a blkdebug interface to this img as 'drive1'
+        result = self.vm.qmp('blockdev-add', options={
+            'id': drive1['id'],
+            'driver': drive1['fmt'],
+            'file': {
+                'driver': 'blkdebug',
+                'image': {
+                    'driver': 'file',
+                    'filename': drive1['file']
+                },
+                'set-state': [{
+                    'event': 'flush_to_disk',
+                    'state': 1,
+                    'new_state': 2
+                }],
+                'inject-error': [{
+                    'event': 'read_aio',
+                    'errno': 5,
+                    'state': 2,
+                    'immediately': False,
+                    'once': True
+                }],
+            }
+        })
+        self.assert_qmp(result, 'return', {})
+
+        # Create bitmaps and full backups for both drives
+        drive0 = self.drives[0]
+        dr0bm0 = self.add_bitmap('bitmap0', drive0)
+        dr1bm0 = self.add_bitmap('bitmap0', drive1)
+        self.create_anchor_backup(drive0)
+        self.create_anchor_backup(drive1)
+        self.assert_no_active_block_jobs()
+        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')))
+        self.hmp_io_writes(drive1['id'], (('0xba', 0, 512),
+                                          ('0xef', '16M', '256k'),
+                                          ('0x46', '32736k', '64k')))
+
+        # Create incremental backup targets
+        target0 = self.prepare_backup(dr0bm0)
+        target1 = self.prepare_backup(dr1bm0)
+
+        # Ask for a new incremental backup per-each drive,
+        # expecting drive1's backup to fail:
+        transaction = [
+            transaction_drive_backup(drive0['id'], target0, sync='dirty-bitmap',
+                                     format=drive0['fmt'], mode='existing',
+                                     bitmap=dr0bm0.name),
+            transaction_drive_backup(drive1['id'], target1, sync='dirty-bitmap',
+                                     format=drive1['fmt'], mode='existing',
+                                     bitmap=dr1bm0.name),
+        ]
+        result = self.vm.qmp('transaction', actions=transaction)
+        self.assert_qmp(result, 'return', {})
+
+        # Observe that drive0's backup is cancelled and drive1 completes with
+        # an error.
+        self.wait_qmp_backup_cancelled(drive0['id'])
+        self.assertFalse(self.wait_qmp_backup(drive1['id']))
+        error = self.vm.event_wait('BLOCK_JOB_ERROR')
+        self.assert_qmp(error, 'data', {'device': drive1['id'],
+                                        'action': 'report',
+                                        'operation': 'read'})
+        self.assertFalse(self.vm.get_qmp_events(wait=False))
+        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.
+        dr0bm0.del_target()
+        dr1bm0.del_target()
+        target0 = self.prepare_backup(dr0bm0)
+        target1 = self.prepare_backup(dr1bm0)
+
+        # Re-run the exact same transaction.
+        result = self.vm.qmp('transaction', actions=transaction)
+        self.assert_qmp(result, 'return', {})
+
+        # Both should complete successfully this time.
+        self.assertTrue(self.wait_qmp_backup(drive0['id']))
+        self.assertTrue(self.wait_qmp_backup(drive1['id']))
+        self.make_reference_backup(dr0bm0)
+        self.make_reference_backup(dr1bm0)
+        self.assertFalse(self.vm.get_qmp_events(wait=False))
+        self.assert_no_active_block_jobs()
+
+        # And the images should of course validate.
+        self.vm.shutdown()
+        self.check_backups()
+
+
     def test_sync_dirty_bitmap_missing(self):
         self.assert_no_active_block_jobs()
         self.files.append(self.err_img)
diff --git a/tests/qemu-iotests/124.out b/tests/qemu-iotests/124.out
index 594c16f..dae404e 100644
--- a/tests/qemu-iotests/124.out
+++ b/tests/qemu-iotests/124.out
@@ -1,5 +1,5 @@
-........
+.........
 ----------------------------------------------------------------------
-Ran 8 tests
+Ran 9 tests
 
 OK
-- 
2.4.2

[Qemu-devel] [RFC 9/9] qmp-commands.hx: Update the supported 'transaction' operations

[Stefan Hajnoczi]

From: Kashyap Chamarthy <kchamart@redhat.com>

Although the canonical source of reference for QMP commands is
qapi-schema.json, for consistency's sake, update qmp-commands.hx to
state the list of supported transactionable operations, namely:

    drive-backup
    blockdev-backup
    blockdev-snapshot-internal-sync
    abort
    block-dirty-bitmap-add
    block-dirty-bitmap-clear

Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qmp-commands.hx | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/qmp-commands.hx b/qmp-commands.hx
index 867a21f..cdab36c 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1238,11 +1238,22 @@ SQMP
 transaction
 -----------
 
-Atomically operate on one or more block devices.  The only supported operations
-for now are drive-backup, internal and external snapshotting.  A list of
-dictionaries is accepted, that contains the actions to be performed.
-If there is any failure performing any of the operations, all operations
-for the group are abandoned.
+Atomically operate on one or more block devices.  Operations that are
+currently supported:
+
+    - drive-backup
+    - blockdev-backup
+    - blockdev-snapshot-sync
+    - blockdev-snapshot-internal-sync
+    - abort
+    - block-dirty-bitmap-add
+    - block-dirty-bitmap-clear
+
+Refer to the qemu/qapi-schema.json file for minimum required QEMU
+versions for these operations.  A list of dictionaries is accepted,
+that contains the actions to be performed.  If there is any failure
+performing any of the operations, all operations for the group are
+abandoned.
 
 For external snapshots, the dictionary contains the device, the file to use for
 the new snapshot, and the format.  The default format, if not specified, is
-- 
2.4.2

Re: [Qemu-devel] [RFC 4/9] block: keep bitmap if incremental backup job is cancelled

[John Snow]

On 06/12/2015 06:09 AM, Stefan Hajnoczi wrote:
> Reclaim the dirty bitmap if an incremental backup block job is
> cancelled.  The ret variable may be 0 when the job is cancelled so it's
> not enough to check ret < 0.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  block/backup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index d3f648d..c1ad975 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -430,7 +430,7 @@ static void coroutine_fn backup_run(void *opaque)
>  
>      if (job->sync_bitmap) {
>          BdrvDirtyBitmap *bm;
> -        if (ret < 0) {
> +        if (ret < 0 || block_job_is_cancelled(&job->common)) {
>              /* Merge the successor back into the parent, delete nothing. */
>              bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
>              assert(bm);
> 

Reviewed-by: John Snow <jsnow@redhat.com>

Re: [Qemu-devel] [RFC 4/9] block: keep bitmap if incremental backup job is cancelled

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1150 bytes --]

On Fri, Jun 12, 2015 at 06:39:19PM -0400, John Snow wrote:
> 
> 
> On 06/12/2015 06:09 AM, Stefan Hajnoczi wrote:
> > Reclaim the dirty bitmap if an incremental backup block job is
> > cancelled.  The ret variable may be 0 when the job is cancelled so it's
> > not enough to check ret < 0.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  block/backup.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/block/backup.c b/block/backup.c
> > index d3f648d..c1ad975 100644
> > --- a/block/backup.c
> > +++ b/block/backup.c
> > @@ -430,7 +430,7 @@ static void coroutine_fn backup_run(void *opaque)
> >  
> >      if (job->sync_bitmap) {
> >          BdrvDirtyBitmap *bm;
> > -        if (ret < 0) {
> > +        if (ret < 0 || block_job_is_cancelled(&job->common)) {
> >              /* Merge the successor back into the parent, delete nothing. */
> >              bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
> >              assert(bm);
> > 
> 
> Reviewed-by: John Snow <jsnow@redhat.com>

Thanks, I'll send this patch separately and CC qemu-stable.

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Re: [Qemu-devel] [RFC 4/9] block: keep bitmap if incremental backup job is cancelled

[Max Reitz]

On 12.06.2015 12:09, Stefan Hajnoczi wrote:
> Reclaim the dirty bitmap if an incremental backup block job is
> cancelled.  The ret variable may be 0 when the job is cancelled so it's
> not enough to check ret < 0.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   block/backup.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/backup.c b/block/backup.c
> index d3f648d..c1ad975 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -430,7 +430,7 @@ static void coroutine_fn backup_run(void *opaque)
>   
>       if (job->sync_bitmap) {
>           BdrvDirtyBitmap *bm;
> -        if (ret < 0) {
> +        if (ret < 0 || block_job_is_cancelled(&job->common)) {
>               /* Merge the successor back into the parent, delete nothing. */
>               bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
>               assert(bm);

Since I can't find a seperate patch on qemu-devel or qemu-block yet:

Reviewed-by: Max Reitz <mreitz@redhat.com>

Re: [Qemu-devel] [RFC 5/9] block: add block job transactions

[Max Reitz]

On 12.06.2015 12:09, Stefan Hajnoczi wrote:
> Sometimes block jobs must execute as a transaction group.  Finishing
> jobs wait until all other jobs are ready to complete successfully.
> Failure or cancellation of one job cancels the other jobs in the group.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   blockjob.c                | 160 ++++++++++++++++++++++++++++++++++++++++++++++
>   include/block/block.h     |   1 +
>   include/block/block_int.h |   3 +-
>   include/block/blockjob.h  |  49 ++++++++++++++
>   trace-events              |   4 ++
>   5 files changed, 216 insertions(+), 1 deletion(-)
>
> diff --git a/blockjob.c b/blockjob.c
> index 2755465..ff622f5 100644
> --- a/blockjob.c
> +++ b/blockjob.c
> @@ -399,3 +399,163 @@ void block_job_defer_to_main_loop(BlockJob *job,
>   
>       qemu_bh_schedule(data->bh);
>   }
> +
> +/* Transactional group of block jobs */
> +struct BlockJobTxn {
> +    /* Jobs may be in different AioContexts so protect all fields */
> +    QemuMutex lock;
> +
> +    /* Reference count for txn object */
> +    unsigned int ref;
> +
> +    /* Is this txn cancelling its jobs? */
> +    bool aborting;
> +
> +    /* Number of jobs still running */
> +    unsigned int jobs_pending;
> +
> +    /* List of jobs */
> +    QLIST_HEAD(, BlockJob) jobs;
> +};
> +
> +BlockJobTxn *block_job_txn_new(void)
> +{
> +    BlockJobTxn *txn = g_new(BlockJobTxn, 1);
> +    qemu_mutex_init(&txn->lock);
> +    txn->ref = 1; /* dropped by block_job_txn_begin() */
> +    txn->aborting = false;
> +    txn->jobs_pending = 0;
> +    QLIST_INIT(&txn->jobs);
> +    return txn;
> +}
> +
> +static void block_job_txn_unref(BlockJobTxn *txn)
> +{
> +    qemu_mutex_lock(&txn->lock);
> +
> +    if (--txn->ref > 0) {
> +        qemu_mutex_unlock(&txn->lock);
> +        return;
> +    }
> +
> +    qemu_mutex_unlock(&txn->lock);
> +    qemu_mutex_destroy(&txn->lock);
> +    g_free(txn);
> +}
> +
> +/* The purpose of this is to keep txn alive until all jobs have been added */
> +void block_job_txn_begin(BlockJobTxn *txn)
> +{
> +    block_job_txn_unref(txn);
> +}
> +
> +void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
> +{
> +    if (!txn) {
> +        return;
> +    }

Do you plan on making use of this case? I'm asking because while I'm 
usually in favor of handling everything gracefully as long as it's easy 
to implement, here I can't think of a case where using NULL with this 
function makes sense, that is to me it would seem like the caller made 
some bad mistake. This in turn would mean that dereferencing a NULL 
pointer or failing an assertion were preferable to hiding that mistake.

Other than this small thing and that it doesn't compile (until patch 7, 
I presume), looks good.

Max

Re: [Qemu-devel] [RFC 5/9] block: add block job transactions

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1096 bytes --]

On Wed, Jun 24, 2015 at 08:37:43PM +0200, Max Reitz wrote:
> On 12.06.2015 12:09, Stefan Hajnoczi wrote:
> >+void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
> >+{
> >+    if (!txn) {
> >+        return;
> >+    }
> 
> Do you plan on making use of this case? I'm asking because while I'm usually
> in favor of handling everything gracefully as long as it's easy to
> implement, here I can't think of a case where using NULL with this function
> makes sense, that is to me it would seem like the caller made some bad
> mistake. This in turn would mean that dereferencing a NULL pointer or
> failing an assertion were preferable to hiding that mistake.
> 
> Other than this small thing and that it doesn't compile (until patch 7, I
> presume), looks good.

Yes.  It is used by backup_start(), which may be called with txn == NULL
by do_drive_backup() from qmp_drive_backup().

It means that blockjob code never needs to check whether it is running
inside a transaction or not.  Blockjob code always calls add_job() and
prepare_to_complete() regardless.

Stefan

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Re: [Qemu-devel] [RFC 4/9] block: keep bitmap if incremental backup job is cancelled

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1193 bytes --]

On Wed, Jun 24, 2015 at 07:35:05PM +0200, Max Reitz wrote:
> On 12.06.2015 12:09, Stefan Hajnoczi wrote:
> >Reclaim the dirty bitmap if an incremental backup block job is
> >cancelled.  The ret variable may be 0 when the job is cancelled so it's
> >not enough to check ret < 0.
> >
> >Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> >---
> >  block/backup.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/block/backup.c b/block/backup.c
> >index d3f648d..c1ad975 100644
> >--- a/block/backup.c
> >+++ b/block/backup.c
> >@@ -430,7 +430,7 @@ static void coroutine_fn backup_run(void *opaque)
> >      if (job->sync_bitmap) {
> >          BdrvDirtyBitmap *bm;
> >-        if (ret < 0) {
> >+        if (ret < 0 || block_job_is_cancelled(&job->common)) {
> >              /* Merge the successor back into the parent, delete nothing. */
> >              bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
> >              assert(bm);
> 
> Since I can't find a seperate patch on qemu-devel or qemu-block yet:
> 
> Reviewed-by: Max Reitz <mreitz@redhat.com>

Thanks, I must have gotten distracted before sending the email.

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