On 04/28/2016 02:58 AM, Alex Bligh wrote: > Allow a client to requests specific bits of information using > NBD_OPT_INFO and thereby signal to the server that it supports them. > This makes it easier for the server to know whether the information > it is providing will be used / respected. > > Now a server can determine whether a client supports block sizes by > the fact it uses NBD_OPT_INFO or NBD_OPT_GO with an NBD_INFO_BLOCK_SIZE, > request as these are part of the same extension, so there is no > need for NBD_OPT_BLOCK_SIZE. > > Signed-off-by: Alex Bligh <[email protected]> > --- > doc/proto.md | 140 > ++++++++++++++++++++++++++++++++++------------------------- > 1 file changed, 80 insertions(+), 60 deletions(-)
> +++ b/doc/proto.md > @@ -636,34 +636,53 @@ This functionality has not yet been implemented by the > reference > implementation, but was implemented by qemu and subsequently > by other users, so has been moved out of the "experimental" section. > > -## Block sizes > +## Block size constraints > > During transmission phase, several operations are constrained by the > export size sent by the final `NBD_OPT_EXPORT_NAME` or `NBD_OPT_GO`, > -as well as by three block sizes defined here (minimum, preferred, and > -maximum). If a client can honor server block sizes (as set out in My fault for introducing it... > -`NBD_OPT_BLOCK_SIZE`), it SHOULD announce this > -during the handshake phase, and SHOULD use `NBD_OPT_GO` rather than > -`NBD_OPT_EXPORT_NAME`. A server SHOULD advertise the block size > -contraints during handshake phase via `NBD_OPT_INFO`. A server > -and client MAY agree on block sizes via out of band means. > - > -If block sizes have not been advertised or agreed on externally, then > -a client SHOULD assume a default minimum block size of 1, a preferred > +as well as by three block size constraints defined here (minimum, > +preferred, and maximum). > + > +If a client can honor server block size constraints (as set out below ...but while you are touching this, s/honor/honour/ so that the document consistently uses UK spellings. > @@ -1077,13 +1093,17 @@ during option haggling in the fixed newstyle > negotiation. > > * `NBD_INFO_BLOCK_SIZE` (3) > > - Represents the server's advertised block sizes; see the "Block > - sizes" section for more details on what these values represent, > - and on constraints on their values. The server MAY send this > - info whether or not the client has negotiated > - `NBD_OPT_BLOCK_SIZE`, and SHOULD send this info if it intends to > - enforce block sizes other than the defaults. The *length* MUST > - be 14, and the reply payload is interpreted as: > + Represents the server's advertised block size constraints; see the > + "Block size constraints" section for more details on what these > + values represent, and on constraints on their values. The server > + MUST send this info if it is requested and it intends to enforce > + block size constraints other than the defaults. After > + sending this information in response to an `NBD_OPT_GO`, s/`NBD_OPT_GO`/`NBD_OPT_GO` where the client requested `NBD_INFO_BLOCK_SIZE`/ > the server > + can legitimately assume that any client that continues the session > + will support the block size constraints supplied (note that this > + assumption cannot be made solely on the basis of an `NBD_OPT_INFO` > + with an `NBD_INFO_BLOCK_SIZE` request). s/request)/request, nor if the client did not request `NBD_INFO_BLOCK_SIZE`)/ > The *length* MUST be 14, > + and the reply payload is interpreted as: > > - 16 bits, `NBD_INFO_BLOCK_SIZE` > - 32 bits, minimum block size > Otherwise I think this is ready. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
------------------------------------------------------------------------------ Find and fix application performance issues faster with Applications Manager Applications Manager provides deep performance insights into multiple tiers of your business applications. It resolves application problems quickly and reduces your MTTR. Get your free trial! https://ad.doubleclick.net/ddm/clk/302982198;130105516;z
_______________________________________________ Nbd-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nbd-general
