Hi Dan/Matt, In the recent LinuxCon Europe Conference, Christoph Hellwig has given a talk on "A Simple, and Scalable pNFS Server For Linux" [1]
During that talk, he has mentioned that for kernel-NFS , LayoutRecall semantics & logic is same as DelegRecall (at least for block & object-type layouts and probably for file layouts too), i.e, for any conflicting access, we need to block that I/O until the layouts are recalled. But I guess in NFS-Ganesha, we do not block the I/Os at the moment while recalling layouts. We would like to know if we need to follow kernel-NFS here or is to left to NFS server implementation to decide when to recall layouts and why we choose not to block the I/Os. Also we seem to be leaving it to FSALs to handle/recall the layouts unlike locks/Delegations whose conflicts are checked in common SAL layer itself. Is there any particular reason behind it? Do we leave the decision when to recall layout and/or block the conflicting I/Os to the FSALs to handle. [1] http://events.linuxfoundation.org/events/linuxcon-europe/program/schedule Thanks, Soumya On 09/24/2015 06:21 PM, Daniel Gryniewicz wrote: > A layout is a guarantee of ownership for the portion of the file > covered. No other conflicting file access can be done while the > layout is granted. So, if conflicting access is needed, the layout > must be recalled. In addition, if something happens in the cluster > that would invalidate that access to that part of the file (such as > loss of a node moving data to a backup node, or cluster optimization > moving the location of the data, or storage nodes partitioning making > the data unavailable, etc.), the layout must be recalled. > > It's probably best to recall layouts via an upcall. VFS is not the > best model to follow here, since it's not a clustered filesystem. > > Dan > > On Thu, Sep 24, 2015 at 5:07 AM, Jiffin Tony Thottan > <jthot...@redhat.com> wrote: >> Hi all, >> >> Currently I am trying to add support for LAYOUTRECALL in FSAL_GLUSTER. >> So I look through other >> FSAL implementation and RFC5661 once again. As far as I understand it is >> a notification send from >> M.D.S. to client demanding back the layouts. First I try to figure out >> scenarios in which layoutrecall >> is useful and following came into my mind(May be I am wrong and also >> please help me finding more) : >> >> 1.) While an I/O is performed , layout of file changes due to a >> gluster-internal process >> >> 2.) two clients performing I/O on same file based on layout provided by >> two different M.D.Ses >> [Currently in FSAL_GLUSTER provides layout for entire file because >> entire file is located on Storage Device] >> >> 3.) When detach a brick from the storage pool in gluster. >> >> But as a second thought , is it necessary to have LAYOUTRECALL ? Layout >> grants permission to a client >> for performing a I/O. But it does not guarantee such that only `this >> client can perform I/O on that`. >> And commenting out LAYOUTRECALL from FSAL_CEPH increases my doubt. >> >> And one more question , FSAL_GPFS introduced LAYOUTRECALL as part of >> UPCALL thread and FSAL_VFS >> as part of a call back thread. So which one will be better should >> handled as part of UPCALL thread or >> separately using another thread ? >> >> Please correct me if anything mentioned above is wrong. >> >> With Regards and Thanks, >> Jiffin >> >> ------------------------------------------------------------------------------ >> Monitor Your Dynamic Infrastructure at Any Scale With Datadog! >> Get real-time metrics from all of your servers, apps and tools >> in one place. >> SourceForge users - Click here to start your Free Trial of Datadog now! >> http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 >> _______________________________________________ >> Nfs-ganesha-devel mailing list >> Nfs-ganesha-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/nfs-ganesha-devel > > ------------------------------------------------------------------------------ > Monitor Your Dynamic Infrastructure at Any Scale With Datadog! > Get real-time metrics from all of your servers, apps and tools > in one place. > SourceForge users - Click here to start your Free Trial of Datadog now! > http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 > _______________________________________________ > Nfs-ganesha-devel mailing list > Nfs-ganesha-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/nfs-ganesha-devel > ------------------------------------------------------------------------------ _______________________________________________ Nfs-ganesha-devel mailing list Nfs-ganesha-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs-ganesha-devel
