> > > +++ b/include/block/block_int.h
> > > @@ -347,6 +347,11 @@ struct BlockDriver {
> > > * clamped to bdrv_getlength() and aligned to request_alignment,
> > > * as well as non-NULL pnum, map, and file; in turn, the driver
> > > * must return an error or set pnum to an aligned non-zero value.
> > > + *
> > > + * Note that @bytes is just a hint on how big of a region the
> > > + * caller wants to inspect. It is not a limit on *pnum.
> > > + * Implementations are free to return larger values of *pnum if
> > > + * doing so does not incur a performance penalty.
> >
> > Worth mention that the cache will benefit of it?
>
> Oh, right, absolutely. Like so:
>
> "block/io.c's bdrv_co_block_status() will clamp *pnum before returning it to
> its caller, but it itself can still make use of the unclamped *pnum value.
> Specifically, the block-status cache for protocol nodes will benefit from
> storing as large a region as possible."
How about this tweak to the wording to make it flow a little better:
block/io.c's bdrv_co_block_status() will utilize an unclamped *pnum
value for the block-status cache on protocol nodes, prior to clamping
*pnum for return to its caller.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
