aio: introduce qemu_get_current_aio_context

This will be used by BDRV_POLL_WHILE (and thus by bdrv_drain)
to choose how to wait for I/O completion.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1477565348-5458-12-git-send-email-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/block/aio.h b/include/block/aio.h
index b9fe2cb37e..040b3b181e 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -453,6 +453,24 @@ static inline bool aio_node_check(AioContext *ctx, bool is_external)
 }
 
 /**
+ * Return the AioContext whose event loop runs in the current thread.
+ *
+ * If called from an IOThread this will be the IOThread's AioContext.  If
+ * called from another thread it will be the main loop AioContext.
+ */
+AioContext *qemu_get_current_aio_context(void);
+
+/**
+ * @ctx: the aio context
+ *
+ * Return whether we are running in the I/O thread that manages @ctx.
+ */
+static inline bool aio_context_in_iothread(AioContext *ctx)
+{
+    return ctx == qemu_get_current_aio_context();
+}
+
+/**
  * aio_context_setup:
  * @ctx: the aio context
  *