On Fri, Apr 14, 2017 at 12:10:03PM -0400, Chuck Lever wrote: > > > On Apr 14, 2017, at 11:56 AM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > > > On Sun, Apr 09, 2017 at 01:06:41PM -0400, Chuck Lever wrote: > >> Observed at Connectathon 2017. > >> > >> If a client has underestimated the size of a Write or Reply chunk, > >> the Linux server writes as much payload data as it can, then it > >> recognizes there was a problem and closes the connection without > >> sending the transport header. > > > > Why would the client underestimate? Is this a client-side bug? > > It can be a bug, and the behavior in this case is that the > client retransmits indefinitely and deadlocks the transport, > because the client's upper layer never sees a reply. > > But as you know there are some NFS operations where the client > cannot predict in advance how large the reply will be. In > particular the upper bound size of an NFSACL GETACL reply or > certain NFSv4 GETATTR attributes are not predictable. Oh, I'd forgotten about those cases. > These > I might categorize as protocol bugs. > > A client can do its best by posting a very large reply buffer > for such operations, but since these situations typically > are in practice rare, but NFSv4 GETATTR can be a relatively > common operation, clients post a few dozen KB for the reply > buffer and call it a day. > > In these cases (if they should ever fail IRL), returning an > error is polite and allows operation of other RPCs on that > transport to continue. Got it, thanks. (I assume this is documented somewhere in the specs?) --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
