On 07/22/2013 03:43 PM, J. Bruce Fields wrote: > On Mon, Jul 22, 2013 at 03:37:00PM -0400, Bryan Schumaker wrote: >> On 07/22/2013 03:30 PM, J. Bruce Fields wrote: >>> On Mon, Jul 22, 2013 at 03:17:29PM -0400, Bryan Schumaker wrote: >>>> On 07/22/2013 02:50 PM, J. Bruce Fields wrote: >>>>> On Fri, Jul 19, 2013 at 05:03:49PM -0400, bjschuma@xxxxxxxxxx wrote: >>>>>> From: Bryan Schumaker <bjschuma@xxxxxxxxxx> >>>>>> >>>>>> Rather than performing the copy right away, schedule it to run later and >>>>>> reply to the client. Later, send a callback to notify the client that >>>>>> the copy has finished. >>>>> >>>>> I believe you need to implement the referring triple support described >>>>> in http://tools.ietf.org/html/rfc5661#section-2.10.6.3 to fix the race >>>>> described in >>>>> http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion2-19#section-15.1.3 >>>>> . >>>> >>>> I'll re-read and re-write. >>>> >>>>> >>>>> I see cb_delay initialized below, but not otherwise used. Am I missing >>>>> anything? >>>> >>>> Whoops! I was using that earlier to try to fake up a callback, but I eventually decided it's easier to just do the copy asynchronously. I must have forgotten to take it out :( >>>> >>>>> >>>>> What about OFFLOAD_STATUS and OFFLOAD_ABORT? >>>> >>>> I haven't thought out those too much... I haven't thought about a use for them on the client yet. >>> >>> If it might be a long-running copy, I assume the client needs the >>> ability to abort if the caller is killed. >>> >>> (Dumb question: what happens on the network partition? Does the server >>> abort the copy when it expires the client state?) >>> >>> In any case, >>> http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion2-19#section-15.1.3 >>> says "If a server's COPY operation returns a stateid, then the server >>> MUST also support these operations: CB_OFFLOAD, OFFLOAD_ABORT, and >>> OFFLOAD_STATUS." >>> >>> So even if we've no use for them on the client then we still need to >>> implement them (and probably just write a basic pynfs test). Either >>> that or update the spec. >> >> Fair enough. I'll think it out and do something! Easy solution: save this patch for later and only support the sync version of copy for the final version of this patch series. > > I can't remember--does the spec give the server a clear way to bail out > and tell the client to fall back on a normal copy in cases where the > server knows the copy could take an unreasonable amount of time? > > --b. I don't think so. Is there ever a case where copying over the network would be slower than copying on the server? > >> >> - Bryan >> >>> >>>>> In some common cases the reply will be very quick, and we might be >>>>> better off handling it synchronously. Could we implement a heuristic >>>>> like "copy synchronously if the filesystem has special support or the >>>>> range is less than the maximum iosize, otherwise copy asynchronously"? >>>> >>>> I'm sure that can be done, I'm just not sure how to do it yet... >>> >>> OK, thanks. >>> >>> --b. >>> >> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
