linux-aio: properly bubble up errors from initialization

laio_init() can fail for a couple of reasons, which will lead to a NULL
pointer dereference in laio_attach_aio_context().

To solve this, add a aio_setup_linux_aio() function which is called
early in raw_open_common. If this fails, propagate the error up. The
signature of aio_get_linux_aio() was not modified, because it seems
preferable to return the actual errno from the possible failing
initialization calls.

Additionally, when the AioContext changes, we need to associate a
LinuxAioState with the new AioContext. Use the bdrv_attach_aio_context
callback and call the new aio_setup_linux_aio(), which will allocate a
new AioContext if needed, and return errors on failures. If it fails for
any reason, fallback to threaded AIO with an error message, as the
device is already in-use by the guest.

Add an assert that aio_get_linux_aio() cannot return NULL.

Signed-off-by: Nishanth Aravamudan <naravamudan@digitalocean.com>
Message-id: 20180622193700.6523-1-naravamudan@digitalocean.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/stubs/linux-aio.c b/stubs/linux-aio.c
index ed47bd443c..84d1f784ae 100644
--- a/stubs/linux-aio.c
+++ b/stubs/linux-aio.c
@@ -21,7 +21,7 @@ void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context)
     abort();
 }
 
-LinuxAioState *laio_init(void)
+LinuxAioState *laio_init(Error **errp)
 {
     abort();
 }