Re: [PATCH 4/4] NFSD: Implement SEEK

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Oct 28, 2013 at 10:57:26AM -0400, Anna Schumaker wrote:
> This patch adds in the SEEK operation used by clients doing an llseek on
> a file to find either hole or data sections in a file.  I'm faking the
> "allocated" status right now, since I haven't quite figured out how to
> tell if a range is allocated on disk yet.
> 
> This patch is missing correctly determining the "allocated" status of
> the HOLE / DATA range.  I expect I'll need to learn all about how fiemap
> works before properly setting these values.
> 
> Signed-off-by: Anna Schumaker <bjschuma@netapp.com>
> ---
>  fs/nfsd/nfs4proc.c   | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  fs/nfsd/nfs4xdr.c    | 40 ++++++++++++++++++++++++++++++++++++++--
>  fs/nfsd/xdr4.h       | 15 +++++++++++++++
>  include/linux/nfs4.h |  2 +-
>  4 files changed, 98 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 3210c6f..bc45ed2 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1064,6 +1064,45 @@ nfsd4_write_plus(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	return nfserr_union_notsupp;
>  }
>  
> +static __be32
> +nfsd4_seek(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> +		struct nfsd4_seek *seek)
> +{
> +	struct file *file;
> +	loff_t pos, end_pos;
> +	__be32 status;
> +
> +	status = nfs4_preprocess_stateid_op(SVC_NET(rqstp), cstate,
> +					    &seek->seek_stateid,
> +					    RD_STATE | WR_STATE, &file);

Note nfs4_preprocess_stateid_op requires the caller to hold the state
lock.  Andyou want to either hold it till you're done using "file" or
take a reference on file before dropping it.

--b.

> +	if (status != nfs_ok)
> +		return status;
> +
> +	if (seek->seek_whence == NFS4_CONTENT_DATA) {
> +		pos = vfs_llseek(file, seek->seek_offset, SEEK_DATA);
> +		end_pos = vfs_llseek(file, pos, SEEK_HOLE);
> +		seek->seek_allocated = true;
> +	} else {
> +		pos = vfs_llseek(file, seek->seek_offset, SEEK_HOLE);
> +		end_pos = vfs_llseek(file, pos, SEEK_DATA);
> +		seek->seek_allocated = false;
> +	}
> +
> +	if (pos < 0)
> +		return nfserrno(pos);
> +	else if (end_pos == -ENXIO) {
> +		seek->seek_length = 0;
> +		seek->seek_eof = true;
> +	} else if (end_pos < 0)
> +		return nfserrno(end_pos);
> +	else
> +		seek->seek_length = end_pos - pos;
> +
> +	seek->seek_offset = pos;
> +
> +	return nfs_ok;
> +}
> +
>  /* This routine never returns NFS_OK!  If there are no other errors, it
>   * will return NFSERR_SAME or NFSERR_NOT_SAME depending on whether the
>   * attributes matched.  VERIFY is implemented by mapping NFSERR_SAME
> @@ -1885,6 +1924,11 @@ static struct nfsd4_operation nfsd4_ops[] = {
>  		.op_rsize_bop = (nfsd4op_rsize)nfsd4_write_rsize,
>  		.op_get_currentstateid = (stateid_getter)nfsd4_get_writestateid,
>  	},
> +
> +	[OP_SEEK] = {
> +		.op_func = (nfsd4op_func)nfsd4_seek,
> +		.op_name = "OP_SEEK",
> +	},
>  };
>  
>  #ifdef NFSD_DEBUG
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 1e4e9af..8434740 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -1511,6 +1511,22 @@ nfsd4_decode_write_plus(struct nfsd4_compoundargs *argp,
>  }
>  
>  static __be32
> +nfsd4_decode_seek(struct nfsd4_compoundargs *argp, struct nfsd4_seek *seek)
> +{
> +	DECODE_HEAD;
> +
> +	status = nfsd4_decode_stateid(argp, &seek->seek_stateid);
> +	if (status)
> +		return status;
> +
> +	READ_BUF(12);
> +	READ64(seek->seek_offset);
> +	READ32(seek->seek_whence);
> +
> +	DECODE_TAIL;
> +}
> +
> +static __be32
>  nfsd4_decode_noop(struct nfsd4_compoundargs *argp, void *p)
>  {
>  	return nfs_ok;
> @@ -1693,7 +1709,7 @@ static nfsd4_dec nfsd42_dec_ops[] = {
>  	[OP_OFFLOAD_STATUS]	= (nfsd4_dec)nfsd4_decode_notsupp,
>  	[OP_WRITE_PLUS]		= (nfsd4_dec)nfsd4_decode_write_plus,
>  	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_notsupp,
> -	[OP_SEEK]		= (nfsd4_dec)nfsd4_decode_notsupp,
> +	[OP_SEEK]		= (nfsd4_dec)nfsd4_decode_seek,
>  	[OP_IO_ADVISE]		= (nfsd4_dec)nfsd4_decode_notsupp,
>  };
>  
> @@ -3650,6 +3666,26 @@ nfsd4_encode_write_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
>  }
>  
>  static __be32
> +nfsd4_encode_seek(struct nfsd4_compoundres *resp, __be32 nfserr,
> +		  struct nfsd4_seek *seek)
> +{
> +	__be32 *p;
> +
> +	if (nfserr)
> +		return nfserr;
> +
> +	RESERVE_SPACE(28);
> +	WRITE32(seek->seek_eof);
> +	WRITE32(seek->seek_whence);
> +	WRITE64(seek->seek_offset);
> +	WRITE64(seek->seek_length);
> +	WRITE32(seek->seek_allocated);
> +	ADJUST_ARGS();
> +
> +	return nfserr;
> +}
> +
> +static __be32
>  nfsd4_encode_noop(struct nfsd4_compoundres *resp, __be32 nfserr, void *p)
>  {
>  	return nfserr;
> @@ -3730,7 +3766,7 @@ static nfsd4_enc nfsd4_enc_ops[] = {
>  	[OP_OFFLOAD_STATUS]	= (nfsd4_enc)nfsd4_encode_noop,
>  	[OP_WRITE_PLUS]		= (nfsd4_enc)nfsd4_encode_write_plus,
>  	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_noop,
> -	[OP_SEEK]		= (nfsd4_enc)nfsd4_encode_noop,
> +	[OP_SEEK]		= (nfsd4_enc)nfsd4_encode_seek,
>  	[OP_IO_ADVISE]		= (nfsd4_enc)nfsd4_encode_noop,
>  };
>  
> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> index aaef9ab..ae9debc 100644
> --- a/fs/nfsd/xdr4.h
> +++ b/fs/nfsd/xdr4.h
> @@ -451,6 +451,20 @@ struct nfsd4_write_plus {
>  	struct nfsd42_write_res	wp_res;
>  };
>  
> +struct nfsd4_seek {
> +	/* request */
> +	stateid_t	seek_stateid;
> +
> +	/* Shared between request and response */
> +	u64		seek_offset;
> +	u32		seek_whence;
> +
> +	/* response */
> +	u32		seek_eof;
> +	u64		seek_length;
> +	u32		seek_allocated;
> +};
> +
>  struct nfsd4_op {
>  	int					opnum;
>  	__be32					status;
> @@ -499,6 +513,7 @@ struct nfsd4_op {
>  
>  		/* NFSv4.2 */
>  		struct nfsd4_write_plus		write_plus;
> +		struct nfsd4_seek		seek;
>  	} u;
>  	struct nfs4_replay *			replay;
>  };
> diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
> index 55ed991..81d6b09 100644
> --- a/include/linux/nfs4.h
> +++ b/include/linux/nfs4.h
> @@ -128,7 +128,7 @@ enum nfs_opnum4 {
>  Needs to be updated if more operations are defined in future.*/
>  
>  #define FIRST_NFS4_OP	OP_ACCESS
> -#define LAST_NFS4_OP 	OP_WRITE_PLUS
> +#define LAST_NFS4_OP 	OP_SEEK
>  
>  enum nfsstat4 {
>  	NFS4_OK = 0,
> -- 
> 1.8.4.1
>