aio: rename aio_context_in_iothread() to in_aio_context_home_thread()

The name aio_context_in_iothread() is misleading because it also returns
true when called on the main AioContext from the main loop thread, which
is not an IOThread.

This patch renames it to in_aio_context_home_thread() and expands the
doc comment to make the semantics clearer.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

include/block/aio.h

@@ -534,11 +534,14 @@ void aio_co_enter(AioContext *ctx, struct Coroutine *co);
 AioContext *qemu_get_current_aio_context(void);
 
 /**
+ * in_aio_context_home_thread:
  * @ctx: the aio context
  *
- * Return whether we are running in the I/O thread that manages @ctx.
+ * Return whether we are running in the thread that normally runs @ctx.  Note
+ * that acquiring/releasing ctx does not affect the outcome, each AioContext
+ * still only has one home thread that is responsible for running it.
  */
-static inline bool aio_context_in_iothread(AioContext *ctx)
+static inline bool in_aio_context_home_thread(AioContext *ctx)
 {
     return ctx == qemu_get_current_aio_context();
 }

include/block/block.h

@@ -372,7 +372,7 @@ void bdrv_drain_all(void);
     bool busy_ = true;                                     \
     BlockDriverState *bs_ = (bs);                          \
     AioContext *ctx_ = bdrv_get_aio_context(bs_);          \
-    if (aio_context_in_iothread(ctx_)) {                   \
+    if (in_aio_context_home_thread(ctx_)) {                \
         while ((cond) || busy_) {                          \
             busy_ = aio_poll(ctx_, (cond));                \
             waited_ |= !!(cond) | busy_;                   \