On Fri, Oct 08, 2021 at 09:20:35AM +0200, Emanuele Giuseppe Esposito wrote:
> 
> > > +/*
> > > + * Global state (GS) API. These functions run under the BQL lock.
> > > + *
> > > + * If a function modifies the graph, it also uses drain and/or
> > > + * aio_context_acquire/release to be sure it has unique access.
> > > + * aio_context locking is needed together with BQL because of
> > > + * the thread-safe I/O API that concurrently runs and accesses
> > > + * the graph without the BQL.
> > > + *
> > > + * It is important to note that not all of these functions are
> > > + * necessarily limited to running under the BQL, but they would
> > > + * require additional auditing and may small thread-safety changes
> > > + * to move them into the I/O API. Often it's not worth doing that
> > > + * work since the APIs are only used with the BQL held at the
> > > + * moment, so they have been placed in the GS API (for now).
> > > + *
> > > + * All functions below must use this assertion:
> > > + * g_assert(qemu_in_main_thread());
> > > + * to catch when they are accidentally called without the BQL.
> > > + */
> > 
> > This is comment is duplicated in many places. I suggest explaining it in
> > one place and using references in the other files:
> > 
> >    /*
> >     * Global state (GS) API. These functions run under the BQL lock.
> >     *
> >     * See include/block/block.h for more information about the GS API.
> >     */
> > 
> 
> Good idea. Should I also do that for I/O, or it's not worth for very few
> lines?

Up to you, but I think it makes sense to have a minimal comment for both
the GS and I/O API.

Stefan