Re: [PATCH 05/12] RFC: nfs: ask for layouttypes during fsinfo call

[Benny Halevy <bhalevy@panasas.com>]

On 2010-09-18 05:17, Fred Isaman wrote:
> From: The pNFS Team <linux-nfs@vger.kernel.org>
> 
> This information will be used to determine which layout driver,
> if any, to use for subsequent IO on this filesystem.  Each driver
> is assigned an integer id, with 0 reserved to indicate no driver.
> 
> The server can in theory return multiple ids.  However, our current
> client implementation only notes the first entry and ignores the
> rest.
> 
> Signed-off-by: TBD - melding/reorganization of several patches
> ---
>  fs/nfs/nfs4proc.c       |    2 +-
>  fs/nfs/nfs4xdr.c        |   57 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/nfs_xdr.h |    1 +
>  3 files changed, 59 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index c46e45e..c0d9ff4 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -129,7 +129,7 @@ const u32 nfs4_fsinfo_bitmap[2] = { FATTR4_WORD0_MAXFILESIZE
>  			| FATTR4_WORD0_MAXREAD
>  			| FATTR4_WORD0_MAXWRITE
>  			| FATTR4_WORD0_LEASE_TIME,
> -			0
> +			FATTR4_WORD1_FS_LAYOUT_TYPES

Note that originally (9170cf5 pnfs_submit: set and unset pnfs layoutdriver modules),
we set this only under CONFIG_NFS_V4_1, but it should be ok to ask for
it anyhow.

Benny

>  };
>  
>  const u32 nfs4_fs_locations_bitmap[2] = {
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index b0bd7ef..e138237 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -3868,6 +3868,60 @@ xdr_error:
>  	return status;
>  }
>  
> +/*
> + * Decode potentially multiple layout types. Currently we only support
> + * one layout driver per file system.
> + */
> +static int decode_first_pnfs_layout_type(struct xdr_stream *xdr,
> +					 uint32_t *layouttype)
> +{
> +	uint32_t *p;
> +	int num;
> +
> +	p = xdr_inline_decode(xdr, 4);
> +	if (unlikely(!p))
> +		goto out_overflow;
> +	num = be32_to_cpup(p);
> +
> +	/* pNFS is not supported by the underlying file system */
> +	if (num == 0) {
> +		*layouttype = 0;
> +		return 0;
> +	}
> +	if (num > 1)
> +		printk(KERN_INFO "%s: Warning: Multiple pNFS layout drivers "
> +			"per filesystem not supported\n", __func__);
> +
> +	/* Decode and set first layout type, move xdr->p past unused types */
> +	p = xdr_inline_decode(xdr, num * 4);
> +	if (unlikely(!p))
> +		goto out_overflow;
> +	*layouttype = be32_to_cpup(p);
> +	return 0;
> +out_overflow:
> +	print_overflow_msg(__func__, xdr);
> +	return -EIO;
> +}
> +
> +/*
> + * The type of file system exported.
> + * Note we must ensure that layouttype is set in any non-error case.
> + */
> +static int decode_attr_pnfstype(struct xdr_stream *xdr, uint32_t *bitmap,
> +				uint32_t *layouttype)
> +{
> +	int status = 0;
> +
> +	dprintk("%s: bitmap is %x\n", __func__, bitmap[1]);
> +	if (unlikely(bitmap[1] & (FATTR4_WORD1_FS_LAYOUT_TYPES - 1U)))
> +		return -EIO;
> +	if (bitmap[1] & FATTR4_WORD1_FS_LAYOUT_TYPES) {
> +		status = decode_first_pnfs_layout_type(xdr, layouttype);
> +		bitmap[1] &= ~FATTR4_WORD1_FS_LAYOUT_TYPES;
> +	} else
> +		*layouttype = 0;
> +	return status;
> +}
>  
>  static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
>  {
> @@ -3894,6 +3948,9 @@ static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
>  	if ((status = decode_attr_maxwrite(xdr, bitmap, &fsinfo->wtmax)) != 0)
>  		goto xdr_error;
>  	fsinfo->wtpref = fsinfo->wtmax;
> +	status = decode_attr_pnfstype(xdr, bitmap, &fsinfo->layouttype);
> +	if (status)
> +		goto xdr_error;
>  
>  	status = verify_attr_len(xdr, savep, attrlen);
>  xdr_error:
> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
> index 172df83..7d68a5c 100644
> --- a/include/linux/nfs_xdr.h
> +++ b/include/linux/nfs_xdr.h
> @@ -113,6 +113,7 @@ struct nfs_fsinfo {
>  	__u32			dtpref;	/* pref. readdir transfer size */
>  	__u64			maxfilesize;
>  	__u32			lease_time; /* in seconds */
> +	__u32			layouttype; /* supported pnfs layout driver */
>  };
>  
>  struct nfs_fsstat {