Re: [PATCH 14/18] nfsd: pNFS block layout driver

J. Bruce Fields
2015-01-06T17:17:05Z

On Tue, Jan 06, 2015 at 05:28:37PM +0100, Christoph Hellwig wrote:
> Add a small shim between core nfsd and filesystems to translate the
> somewhat cumbersome pNFS data structures and semantics to something
> more palatable for Linux filesystems.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> .../filesystems/nfs/pnfs-block-server.txt | 40 +++++
> fs/nfsd/Makefile | 2 +-
> fs/nfsd/blocklayout.c | 194 +++++++++++++++++++++
> fs/nfsd/blocklayoutxdr.c | 157 +++++++++++++++++
> fs/nfsd/blocklayoutxdr.h | 62 +++++++
> fs/nfsd/nfs4layouts.c | 7 +
> fs/nfsd/pnfs.h | 1 +
> 7 files changed, 462 insertions(+), 1 deletion(-)
> create mode 100644 Documentation/filesystems/nfs/pnfs-block-server.txt
> create mode 100644 fs/nfsd/blocklayout.c
> create mode 100644 fs/nfsd/blocklayoutxdr.c
> create mode 100644 fs/nfsd/blocklayoutxdr.h
>
> diff --git a/Documentation/filesystems/nfs/pnfs-block-server.txt b/Documentation/filesystems/nfs/pnfs-block-server.txt
> new file mode 100644
> index 0000000..f45d399
> --- /dev/null
> +++ b/Documentation/filesystems/nfs/pnfs-block-server.txt
> @@ -0,0 +1,40 @@
> +pNFS block layout server user guide
> +
> +The Linux NFS server now supports the pNFS block layout extension. In this
> +case the NFS server acts as Metadata Server (MDS) for pNFS, which in addition
> +to handling all the metadata access to the NFS export also hands out layouts
> +to the clients to directly access the underlying block devices that is

s/is/are/.

> +shared with the client. Note that there are no Data Servers (DSs) in the
> +block layout flavor of pNFS.
> +
> +To use pNFS block layouts with with the Linux NFS server the exported file
> +system needs to support the pNFS block layouts (current just XFS), and the
> +file system must sit on shared storage (typically iSCSI) that is accessible
> +to the clients as well as the server. The file system needs to either sit
> +directly on the exported volume, or on a RAID 0 using the MD software RAID
> +driver with the version 1 superblock format. If the filesystem uses sits
> +on a RAID 0 device the clients will automatically stripe their I/O over
> +multiple LUNs.
> +
> +On the server pNFS block volume support is automatically if the file system

s/automatically/automatically enabled/.

So there's no server-side configuration required at all?

--b.

> +support its. On the client make sure the kernel has the CONFIG_PNFS_BLOCK
> +option enabled, the blkmapd daemon from nfs-utils is running, and the
> +file system, is mounted using the NFSv4.1 protocol version (mount -o vers=4.1).
> +
> +If the nfsd server needs to fence a non-responding client it calls
> +/sbin/nfsd-recall-failed with the first argument set to the IP address of
> +the client, and the second argument set to the device node without the /dev
> +prefix for the filesystem to be fenced. Below is an example file that show
> +how to translate the device into a serial number from SCSI EVPD 0x80:
...