> -----Original Message----- > From: J. Bruce Fields [mailto:bfields@xxxxxxxxxxxx] > Sent: Thursday, August 04, 2011 12:27 PM > To: Myklebust, Trond > Cc: Venkateswararao Jujjuri; Chuck Lever; linux-nfs@xxxxxxxxxxxxxxx > Subject: Re: State of NFSv4 VolatileFilehandles > > On Thu, Aug 04, 2011 at 12:10:44PM -0400, Trond Myklebust wrote: > > On Thu, 2011-08-04 at 12:03 -0400, J. Bruce Fields wrote: > > > On Thu, Aug 04, 2011 at 04:27:33AM -0700, Venkateswararao Jujjuri > wrote: > > > > One of the usecase is rsync between two physical filesystems; but > in > > > > this particular use case the export > > > > is readonly (rootfs). As trond mentioned Volatile FHs are fine > in > > > > the case of readonly exports. > > > > Is it something we can consider for upstream? VFH only for > readonly > > > > exports.? > > > > > > The client has no way of knowing that an export is read only. (Or > that > > > the server guarantees the safety of looking up names again in the > more > > > general cases Neil describes.) Unless we decide that a server is > making > > > an implicit guarantee of that just by exposing volatile filehandles > at > > > all. Doesn't sound like the existing spec really says that, > though. > > > > NFSv4.1 introduces the 'fs_status' recommended attribute (see section > > 11.11 in RFC5661), which does, in fact, allow the client to deduce > that > > an export is read-only/won't ever change. > > Oh, neat, I'd forgotten that; you're thinking of STATUS4_FIXED? But > I'm > not sure it does the job: > > STATUS4_FIXED, which indicates a read-only image in the sense > that it will never change. The possibility is allowed that, as > a result of migration or switch to a different image, changed > data can be accessed, but within the confines of this instance, > no change is allowed. The client can use this fact to cache > aggressively. > > OK, so permission to set your attribute cache timeout very high, > perhaps, but I don't see why "changed data" couldn't mean changed > paths.... No, but you can presumably use the FSLI4BX_CLSIMUL flag from fs_locations_info in order to find an equivalent replica. Cheers, Trond -- 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
