[Qemu-devel] [PATCH 1/2] Add no-op aio emulation stub

[Alexander Graf <agraf@suse.de>]

We need to be able to do nothing in AIO fashion. Since I suspect this
could be useful for more cases than the non flushing, I figured I'd
create a new function that does everything AIO-like, but doesn't do
anything.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 block.c |   18 ++++++++++++++++++
 block.h |    5 +++++
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 48305b7..1cd39d7 100644
--- a/block.c
+++ b/block.c
@@ -2196,6 +2196,24 @@ static BlockDriverAIOCB *bdrv_aio_flush_em(BlockDriverState *bs,
     return &acb->common;
 }
 
+BlockDriverAIOCB *bdrv_aio_noop_em(BlockDriverState *bs,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    BlockDriverAIOCBSync *acb;
+
+    acb = qemu_aio_get(&bdrv_em_aio_pool, bs, cb, opaque);
+    acb->is_write = 1; /* don't bounce in the completion hadler */
+    acb->qiov = NULL;
+    acb->bounce = NULL;
+    acb->ret = 0;
+
+    if (!acb->bh)
+        acb->bh = qemu_bh_new(bdrv_aio_bh_cb, acb);
+
+    qemu_bh_schedule(acb->bh);
+    return &acb->common;
+}
+
 /**************************************************************/
 /* sync block device emulation */
 
diff --git a/block.h b/block.h
index f87d24e..bef6358 100644
--- a/block.h
+++ b/block.h
@@ -33,6 +33,7 @@ typedef struct QEMUSnapshotInfo {
 #define BDRV_O_CACHE_WB    0x0040 /* use write-back caching */
 #define BDRV_O_NATIVE_AIO  0x0080 /* use native AIO instead of the thread pool */
 #define BDRV_O_NO_BACKING  0x0100 /* don't open the backing file */
+#define BDRV_O_NOFLUSH     0x0200 /* don't flush the image ever */
 
 #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_CACHE_WB)
 
@@ -97,6 +98,10 @@ BlockDriverAIOCB *bdrv_aio_flush(BlockDriverState *bs,
 				 BlockDriverCompletionFunc *cb, void *opaque);
 void bdrv_aio_cancel(BlockDriverAIOCB *acb);
 
+/* Emulate a no-op */
+BlockDriverAIOCB *bdrv_aio_noop_em(BlockDriverState *bs,
+        BlockDriverCompletionFunc *cb, void *opaque);
+
 typedef struct BlockRequest {
     /* Fields to be filled by multiwrite caller */
     int64_t sector;
-- 
1.6.0.2