[Qemu-devel] [PATCH 10/12] block: Add "drained begin/end" for internal snapshot

[Fam Zheng]

This ensures the atomicity of the transaction by avoiding processing of
external requests such as those from ioeventfd.

state->bs is assigned right after bdrv_drained_begin. Because it was
used as the flag for deletion or not in abort, now we need a separate
flag - InternalSnapshotState.created.

Signed-off-by: Fam Zheng <f...@redhat.com>
---
 blockdev.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 015afbf..c3da2c6 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1280,6 +1280,7 @@ typedef struct InternalSnapshotState {
     BlockDriverState *bs;
     AioContext *aio_context;
     QEMUSnapshotInfo sn;
+    bool created;
 } InternalSnapshotState;
 
 static void internal_snapshot_prepare(BlkTransactionState *common,
@@ -1318,6 +1319,8 @@ static void internal_snapshot_prepare(BlkTransactionState 
*common,
     /* AioContext is released in .clean() */
     state->aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(state->aio_context);
+    bdrv_drained_begin(bs);
+    state->bs = bs;
 
     if (!bdrv_is_inserted(bs)) {
         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
@@ -1375,7 +1378,7 @@ static void internal_snapshot_prepare(BlkTransactionState 
*common,
     }
 
     /* 4. succeed, mark a snapshot is created */
-    state->bs = bs;
+    state->created = true;
 }
 
 static void internal_snapshot_abort(BlkTransactionState *common)
@@ -1386,7 +1389,7 @@ static void internal_snapshot_abort(BlkTransactionState 
*common)
     QEMUSnapshotInfo *sn = &state->sn;
     Error *local_error = NULL;
 
-    if (!bs) {
+    if (!state->created) {
         return;
     }
 
@@ -1407,6 +1410,7 @@ static void internal_snapshot_clean(BlkTransactionState 
*common)
                                              common, common);
 
     if (state->aio_context) {
+        bdrv_drained_end(state->bs);
         aio_context_release(state->aio_context);
     }
 }
-- 
2.5.3