Re: [Qemu-devel] [PATCH v2] support add-cow format

[Paolo Bonzini]

On 09/23/2011 02:20 PM, Kevin Wolf wrote:
+static BlockDriverAIOCB *add_cow_aio_flush(BlockDriverState *bs,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    BDRVAddCowState *state = bs->opaque;
+    bdrv_aio_flush(state->image_hd, cb, opaque);
+    return bdrv_aio_flush(bs->file, cb, opaque);

This will invoke the callback twice, and opaque will probably be invalid
after the first callback. Not good.

This code is also lacking error handling for the ifrst bdrv_aio_flush.

I'll repost the NBD series today, so that Dong Xu Wang can implement 
this as co_flush.

Paolo