Re: [PATCH 08/13] RFC: pnfs: filelayout: introduce minimal file layout driver

[Trond Myklebust <Trond.Myklebust@netapp.com>]

On Thu, 2010-09-02 at 14:00 -0400, Fred Isaman wrote:
> From: The pNFS Team <linux-nfs@vger.kernel.org>
> 
> This driver just registers itself and supplies trivial mount/umount functions.
> 
> Signed-off-by: TBD - melding/reorganization of several patches
> ---
>  fs/nfs/Kconfig          |    5 +++
>  fs/nfs/Makefile         |    3 ++
>  fs/nfs/nfs4filelayout.c |   89 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/nfs_fs.h  |    1 +
>  4 files changed, 98 insertions(+), 0 deletions(-)
>  create mode 100644 fs/nfs/nfs4filelayout.c
> 
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index 5f1b936..980f2dc 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -82,6 +82,11 @@ config NFS_V4_1
>  
>  	  If unsure, say N.
>  
> +config PNFS_FILE_LAYOUT
> +	tristate
> +	depends on NFS_FS && NFS_V4_1
> +	default m

Should be 'default y', otherwise it has an implicit dependency on
CONFIG_MODULES.

> +
>  config ROOT_NFS
>  	bool "Root file system on NFS"
>  	depends on NFS_FS=y && IP_PNP
> diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
> index bb9e773..08a8889 100644
> --- a/fs/nfs/Makefile
> +++ b/fs/nfs/Makefile
> @@ -18,3 +18,6 @@ nfs-$(CONFIG_NFS_V4)	+= nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o \
>  nfs-$(CONFIG_NFS_V4_1)	+= pnfs.o
>  nfs-$(CONFIG_SYSCTL) += sysctl.o
>  nfs-$(CONFIG_NFS_FSCACHE) += fscache.o fscache-index.o
> +
> +obj-$(CONFIG_PNFS_FILE_LAYOUT) += nfs_layout_nfsv41_files.o
> +nfs_layout_nfsv41_files-y := nfs4filelayout.o
> diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
> new file mode 100644
> index 0000000..c685196
> --- /dev/null
> +++ b/fs/nfs/nfs4filelayout.c
> @@ -0,0 +1,89 @@
> +/*
> + *  Module for the pnfs nfs4 file layout driver.
> + *  Defines all I/O and Policy interface operations, plus code
> + *  to register itself with the pNFS client.
> + *
> + *  Copyright (c) 2002
> + *  The Regents of the University of Michigan
> + *  All Rights Reserved
> + *
> + *  Dean Hildebrand <dhildebz@umich.edu>
> + *
> + *  Permission is granted to use, copy, create derivative works, and
> + *  redistribute this software and such derivative works for any purpose,
> + *  so long as the name of the University of Michigan is not used in
> + *  any advertising or publicity pertaining to the use or distribution
> + *  of this software without specific, written prior authorization. If
> + *  the above copyright notice or any other identification of the
> + *  University of Michigan is included in any copy of any portion of
> + *  this software, then the disclaimer below must also be included.
> + *
> + *  This software is provided as is, without representation or warranty
> + *  of any kind either express or implied, including without limitation
> + *  the implied warranties of merchantability, fitness for a particular
> + *  purpose, or noninfringement.  The Regents of the University of
> + *  Michigan shall not be liable for any damages, including special,
> + *  indirect, incidental, or consequential damages, with respect to any
> + *  claim arising out of or in connection with the use of the software,
> + *  even if it has been or is hereafter advised of the possibility of
> + *  such damages.
> + */
> +
> +#include <linux/nfs_fs.h>
> +#include "pnfs.h"
> +
> +#define NFSDBG_FACILITY         NFSDBG_PNFS_LD
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Dean Hildebrand <dhildebz@umich.edu>");
> +MODULE_DESCRIPTION("The NFSv4 file layout driver");
> +
> +int
> +filelayout_initialize_mountpoint(struct nfs_client *clp)
> +{
> +	return 0;
> +}
> +
> +int
> +filelayout_uninitialize_mountpoint(struct nfs_client *clp)
> +{
> +	dprintk("--> %s\n", __func__);
> +
> +	return 0;
> +}
> +
> +struct layoutdriver_io_operations filelayout_io_operations = {

Should definitely be declared as 'const' (and possibly 'static').

> +	.initialize_mountpoint   = filelayout_initialize_mountpoint,
> +	.uninitialize_mountpoint = filelayout_uninitialize_mountpoint,
> +};
> +
> +
> +struct pnfs_layoutdriver_type filelayout_type = {

Ditto.

> +	.id = LAYOUT_NFSV4_1_FILES,
> +	.name = "LAYOUT_NFSV4_1_FILES",
> +	.ld_io_ops = &filelayout_io_operations,

Why do we need a separate 'struct layoutdriver_io_operations'? Any
reason those can't just be embedded in struct pnfs_layoutdriver_type?

> +};
> +
> +static int __init nfs4filelayout_init(void)
> +{
> +	printk(KERN_INFO "%s: NFSv4 File Layout Driver Registering...\n",
> +	       __func__);
> +
> +	/*
> +	 * Need to register file_operations struct with global list to indicate
> +	 * that NFS4 file layout is a possible pNFS I/O module
> +	 */
> +	return pnfs_register_layoutdriver(&filelayout_type);
> +}
> +
> +static void __exit nfs4filelayout_exit(void)
> +{
> +	printk(KERN_INFO "%s: NFSv4 File Layout Driver Unregistering...\n",
> +	       __func__);
> +
> +	/* Unregister NFS4 file layout driver with pNFS client*/
> +	pnfs_unregister_layoutdriver(&filelayout_type);
> +}
> +
> +module_init(nfs4filelayout_init);
> +module_exit(nfs4filelayout_exit);
> diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
> index 042c2bd..a0f49a3 100644
> --- a/include/linux/nfs_fs.h
> +++ b/include/linux/nfs_fs.h
> @@ -614,6 +614,7 @@ extern void * nfs_root_data(void);
>  #define NFSDBG_MOUNT		0x0400
>  #define NFSDBG_FSCACHE		0x0800
>  #define NFSDBG_PNFS		0x1000
> +#define NFSDBG_PNFS_LD		0x2000
>  #define NFSDBG_ALL		0xFFFF
>  
>  #ifdef __KERNEL__