Switch blk_aio_*() APIs over to multi-queue by using
qemu_get_current_aio_context() instead of blk_get_aio_context(). This
change will allow devices to process I/O in multiple IOThreads in the
future.

I audited existing blk_aio_*() callers:
- migration/block.c: blk_mig_lock() protects the data accessed by the
  completion callback.
- The remaining emulated devices and exports run with
  qemu_get_aio_context() == blk_get_aio_context().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/block-backend.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index a77295a198..4863be5691 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1530,7 +1530,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
     acb->blk = blk;
     acb->ret = ret;
 
-    replay_bh_schedule_oneshot_event(blk_get_aio_context(blk),
+    replay_bh_schedule_oneshot_event(qemu_get_current_aio_context(),
                                      error_callback_bh, acb);
     return &acb->common;
 }
@@ -1584,11 +1584,11 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset,
     acb->has_returned = false;
 
     co = qemu_coroutine_create(co_entry, acb);
-    aio_co_enter(blk_get_aio_context(blk), co);
+    aio_co_enter(qemu_get_current_aio_context(), co);
 
     acb->has_returned = true;
     if (acb->rwco.ret != NOT_DONE) {
-        replay_bh_schedule_oneshot_event(blk_get_aio_context(blk),
+        replay_bh_schedule_oneshot_event(qemu_get_current_aio_context(),
                                          blk_aio_complete_bh, acb);
     }
 
-- 
2.41.0

On Tue, Sep 12, 2023 at 07:10:35PM -0400, Stefan Hajnoczi wrote:
> Switch blk_aio_*() APIs over to multi-queue by using
> qemu_get_current_aio_context() instead of blk_get_aio_context(). This
> change will allow devices to process I/O in multiple IOThreads in the
> future.
> 
> I audited existing blk_aio_*() callers:
> - migration/block.c: blk_mig_lock() protects the data accessed by the
>   completion callback.
> - The remaining emulated devices and exports run with
>   qemu_get_aio_context() == blk_get_aio_context().
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  block/block-backend.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org