Re: [Nbd] [PATCH] proto: add 'shift' extension.

[Kevin Wolf <kwolf@...696...>]

Am 27.09.2016 um 20:59 hat Denis V. Lunev geschrieben:
> On 09/27/2016 08:04 PM, Paolo Bonzini wrote:
> >
> > On 27/09/2016 15:28, Denis V. Lunev wrote:
> >> On 09/27/2016 03:07 PM, Paolo Bonzini wrote:
> >>> ----- Original Message -----
> >>>> From: "Denis V. Lunev" <den@...2319...>
> >>>> To: "Paolo Bonzini" <pbonzini@...696...>
> >>>> Cc: "Vladimir Sementsov-Ogievskiy" <vsementsov@...2319...>, qemu-devel@...530..., qemu-block@...530...,
> >>>> nbd-general@lists.sourceforge.net, alex@...872..., eblake@...696..., kwolf@...696..., stefanha@...696...,
> >>>> w@...112...
> >>>> Sent: Tuesday, September 27, 2016 12:25:54 PM
> >>>> Subject: Re: [PATCH] proto: add 'shift' extension.
> >>>>
> >>>> On 09/27/2016 01:15 PM, Paolo Bonzini wrote:
> >>>>>> We could go in a different direction and export flag
> >>>>>> 'has_zero_init' which will report that the storage is
> >>>>>> initialized with all zeroes at the moment. In this
> >>>>>> case mirroring code will not fall into this
> >>>>>> branch.
> >>>>> Why don't you add the zero_init flag to QEMU's NBD driver instead?
> >>>> for all cases without knowing real backend on the server side?
> >>>> I think this would be wrong.
> >>> Add it to the command line, and leave it to libvirt or the user to
> >>> pass "-drive file.driver=nbd,...,file.zero-init=on".
> >> I have started with something very similar for 'drive-mirror' command.
> >> We have added additional flag for this to improve migration speed
> >> and this was rejected.
> > You can add it through the filename path too, through a URI option
> > "nbd://...?zero-init=on".
> >
> > Paolo
> ha, cool idea! Thanks!

What's the advantage of writing "?zero-init=on" instead of
",zero-init=on"? Doesn't it only add more string parsing code for no
benefit?

Kevin