Re: [Qemu-devel] RFC: Let NBD client request read-only mode

2017-12-01 Thread Wouter Verhelst
On Thu, Nov 30, 2017 at 10:00:46AM -0600, Eric Blake wrote: > On 11/30/2017 09:32 AM, Wouter Verhelst wrote: > > > A client that wants to be read-only, but which does not see server support > > > (in idea 1, the server did not advertise the bit; in idea 2, the server > > > replies with NBD_REP_ERR_

Re: [Qemu-devel] RFC: Let NBD client request read-only mode

2017-11-30 Thread Eric Blake
On 11/30/2017 09:32 AM, Wouter Verhelst wrote: A client that wants to be read-only, but which does not see server support (in idea 1, the server did not advertise the bit; in idea 2, the server replies with NBD_REP_ERR_UNSUP), does not have to do anything special (it is always possible to do jus

Re: [Qemu-devel] RFC: Let NBD client request read-only mode

2017-11-30 Thread Wouter Verhelst
On Wed, Nov 29, 2017 at 08:57:20AM -0600, Eric Blake wrote: > Right now, only the server can choose whether an export is read-only. A > client can always treat an export as read-only by not sending any writes, > but a server has no guarantee that a client will behave that way, and must > assume th

[Qemu-devel] RFC: Let NBD client request read-only mode

2017-11-29 Thread Eric Blake
Right now, only the server can choose whether an export is read-only. A client can always treat an export as read-only by not sending any writes, but a server has no guarantee that a client will behave that way, and must assume that an export where the server did not advertise NBD_FLAG_READ_ON