Re: [Qemu-devel] [PATCH v3 1/8] block: add bdrv_add_before_write_cb()

[Stefan Hajnoczi]

On Wed, May 15, 2013 at 04:42:57PM +0200, Paolo Bonzini wrote:
> Il 15/05/2013 16:34, Stefan Hajnoczi ha scritto:
> > The bdrv_add_before_write_cb() function installs a callback that is
> > invoked before a write request is processed.  This will be used to
> > implement copy-on-write point-in-time snapshots where we need to copy
> > out old data before overwriting it.
> 
> Perhaps a notifier list that receives the BdrvTrackedRequest?  (BTW we
> should probably remove all the notifier_remove wrappers, they're useless).

Nice idea, done in v4.  I originally rejected NotifierList because it
only has a void * argument, but BdrvRequest has the information we need.