On Tue, Dec 01, 2020 at 12:39:11AM +0000, Trond Myklebust wrote: > On Mon, 2020-11-30 at 18:05 -0500, J. Bruce Fields wrote: > > On Mon, Nov 30, 2020 at 04:24:54PM -0500, trondmy@xxxxxxxxxx wrote: > > > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > > > > > > If the underlying filesystem times out, then we want knfsd to > > > return > > > NFSERR_JUKEBOX/DELAY rather than NFSERR_STALE. > > > > Out of curiosity, what was causing ETIMEDOUT in practice? > > > > If you're only re-exporting NFS from a single server, then it is OK to > use hard mounts. However if you are exporting from multiple servers, or > you have local filesystems that are also being exported by the same > knfsd server, then you usually want to use softerr mounts for NFS so > that operations that take an inordinate amount of time due to temporary > server outages get converted into JUKEBOX/DELAY errors. Otherwise, it > is really simple to cause all the nfsd threads to hang on that one > delinquent server. Makes sense, thanks. In theory the same thing could happen with block devices; longer term I wonder if it'd make sense to limit how many threads are waiting on a single backend. (ACK to the patch, though, that'd be a project for another day.) --b.
