On Thu, Aug 9, 2012 at 10:36 PM, Myklebust, Trond <Trond.Myklebust@xxxxxxxxxx> wrote: > 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? > That's my (maybe mis-)understanding of how server works... But looking at rfc5661 section 18.44.3. layoutreturn implementation. " After this call, the client MUST NOT use the returned layout(s) and the associated storage protocol to access the file data. " And given commit 0a57cdac3f, client is using the layout even after layoutreturn, which IMHO is a violation of 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. > If you still consider it following rfc5661, I'd choose to disable layoutreturn in before write-through-MDS for blocklayout, by adding some flag like PNFS_NO_LAYOUTRET_ON_FALLTHRU similar to objects' PNFS_LAYOUTRET_ON_SETATTR. -- Thanks, Tao -- 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
