On Thu, 2012-08-09 at 22:30 +0800, Peng Tao wrote:
> On Thu, Aug 9, 2012 at 4:21 AM, Trond Myklebust
> <Trond.Myklebust@xxxxxxxxxx> wrote:
> > Ever since commit 0a57cdac3f (NFSv4.1 send layoutreturn to fence
> > disconnected data server) we've been sending layoutreturn calls
> > while there is potentially still outstanding I/O to the data
> > servers. The reason we do this is to avoid races between replayed
> > writes to the MDS and the original writes to the DS.
> >
> > When this happens, the BUG_ON() in nfs4_layoutreturn_done can
> > be triggered because it assumes that we would never call
> > layoutreturn without knowing that all I/O to the DS is
> > finished. The fix is to remove the BUG_ON() now that the
> > assumptions behind the test are obsolete.
> >
> Isn't MDS supposed to recall the layout if races are possible between
> outstanding write-to-DS and write-through-MDS?
Where do you read that in RFC5661?
> And it causes data corruption for blocklayout if client returns layout
> while there is in-flight disk IO...
Then it needs to turn off fast failover to write-through-MDS.
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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