Am 16.09.2014 um 14:59 hat Paolo Bonzini geschrieben: > Il 16/09/2014 14:52, Kevin Wolf ha scritto: > > Yes, that's true. We can't fix this problem in qcow2, though, because > > it's a more general one. I think we must make sure that > > bdrv_invalidate_cache() doesn't yield. > > > > Either by forbidding to run bdrv_invalidate_cache() in a coroutine and > > moving the problem to the caller (where and why is it even called from a > > coroutine?), or possibly by creating a new coroutine for the driver > > callback and running that in a nested event loop that only handles > > bdrv_invalidate_cache() callbacks, so that the NBD server doesn't get a > > chance to process new requests in this thread. > > Incoming migration runs in a coroutine (the coroutine entry point is > process_incoming_migration_co). But everything after qemu_fclose() can > probably be moved into a separate bottom half, so that it gets out of > coroutine context.
Alexey, you should probably rather try this (and add a bdrv_drain_all() in bdrv_invalidate_cache) than messing around with qcow2 locks. This isn't a problem that can be completely fixed in qcow2. Kevin