diff mbox series

[v5,2/5] NFSD: Add READ_PLUS data support

Message ID 20200908162559.509113-3-Anna.Schumaker@Netapp.com (mailing list archive)
State New, archived
Headers show
Series NFSD: Add support for the v4.2 READ_PLUS operation | expand

Commit Message

Anna Schumaker Sept. 8, 2020, 4:25 p.m. UTC 
From: Anna Schumaker <Anna.Schumaker@Netapp.com>

This patch adds READ_PLUS support for returning a single
NFS4_CONTENT_DATA segment to the client. This is basically the same as
the READ operation, only with the extra information about data segments.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

---
v5: Fix up nfsd4_read_plus_rsize() calculation
---
 fs/nfsd/nfs4proc.c | 20 +++++++++++
 fs/nfsd/nfs4xdr.c  | 83 ++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 101 insertions(+), 2 deletions(-)

Comments

Bruce Fields Sept. 8, 2020, 7:42 p.m. UTC | #1 
On Tue, Sep 08, 2020 at 12:25:56PM -0400, schumaker.anna@gmail.com wrote:
> From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> 
> This patch adds READ_PLUS support for returning a single
> NFS4_CONTENT_DATA segment to the client. This is basically the same as
> the READ operation, only with the extra information about data segments.
> 
> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> 
> ---
> v5: Fix up nfsd4_read_plus_rsize() calculation
> ---
>  fs/nfsd/nfs4proc.c | 20 +++++++++++
>  fs/nfsd/nfs4xdr.c  | 83 ++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 101 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index eaf50eafa935..0a3df5f10501 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -2591,6 +2591,19 @@ static inline u32 nfsd4_read_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
>  	return (op_encode_hdr_size + 2 + XDR_QUADLEN(rlen)) * sizeof(__be32);
>  }
>  
> +static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> +{
> +	u32 maxcount = svc_max_payload(rqstp);
> +	u32 rlen = min(op->u.read.rd_length, maxcount);
> +	/*
> +	 * Worst case is a single large data segment, so make
> +	 * sure we have enough room to encode that
> +	 */

After the last patch we allow an unlimited number of segments.  So a
zillion 1-byte segments is also possible, and is a worse case.

Possible ways to avoid that kind of thing:

	- when encoding, stop and return a short read if the xdr-encoded
	  result would exceed the limit calculated here.
	- round SEEK_HOLE results up to the nearest (say) 512 bytes, and
	  SEEK_DATA result down to the nearest 512 bytes.  May also need
	  some logic to avoid encoding 0-length segments.
	- talk to linux-fsdevel, see if we can get a minimum hole
	  alignment guarantee from filesystems.

I'm thinking #1 is simplest.

--b.

> +	u32 seg_len = 1 + 2 + 1;
> +
> +	return (op_encode_hdr_size + 2 + seg_len + XDR_QUADLEN(rlen)) * sizeof(__be32);
> +}
> +
>  static inline u32 nfsd4_readdir_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
>  {
>  	u32 maxcount = 0, rlen = 0;
> @@ -3163,6 +3176,13 @@ static const struct nfsd4_operation nfsd4_ops[] = {
>  		.op_name = "OP_COPY",
>  		.op_rsize_bop = nfsd4_copy_rsize,
>  	},
> +	[OP_READ_PLUS] = {
> +		.op_func = nfsd4_read,
> +		.op_release = nfsd4_read_release,
> +		.op_name = "OP_READ_PLUS",
> +		.op_rsize_bop = nfsd4_read_plus_rsize,
> +		.op_get_currentstateid = nfsd4_get_readstateid,
> +	},
>  	[OP_SEEK] = {
>  		.op_func = nfsd4_seek,
>  		.op_name = "OP_SEEK",
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 0be194de4888..26d12e3edf33 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2173,7 +2173,7 @@ static const nfsd4_dec nfsd4_dec_ops[] = {
>  	[OP_LAYOUTSTATS]	= (nfsd4_dec)nfsd4_decode_notsupp,
>  	[OP_OFFLOAD_CANCEL]	= (nfsd4_dec)nfsd4_decode_offload_status,
>  	[OP_OFFLOAD_STATUS]	= (nfsd4_dec)nfsd4_decode_offload_status,
> -	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_notsupp,
> +	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_read,
>  	[OP_SEEK]		= (nfsd4_dec)nfsd4_decode_seek,
>  	[OP_WRITE_SAME]		= (nfsd4_dec)nfsd4_decode_notsupp,
>  	[OP_CLONE]		= (nfsd4_dec)nfsd4_decode_clone,
> @@ -4597,6 +4597,85 @@ nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
>  		return nfserr_resource;
>  	p = xdr_encode_hyper(p, os->count);
>  	*p++ = cpu_to_be32(0);
> +	return nfserr;
> +}
> +
> +static __be32
> +nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> +			    struct nfsd4_read *read,
> +			    unsigned long maxcount,  u32 *eof)
> +{
> +	struct xdr_stream *xdr = &resp->xdr;
> +	struct file *file = read->rd_nf->nf_file;
> +	int starting_len = xdr->buf->len;
> +	__be32 nfserr;
> +	__be32 *p, tmp;
> +	__be64 tmp64;
> +
> +	/* Content type, offset, byte count */
> +	p = xdr_reserve_space(xdr, 4 + 8 + 4);
> +	if (!p)
> +		return nfserr_resource;
> +
> +	read->rd_vlen = xdr_reserve_space_vec(xdr, resp->rqstp->rq_vec, maxcount);
> +	if (read->rd_vlen < 0)
> +		return nfserr_resource;
> +
> +	nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
> +			    resp->rqstp->rq_vec, read->rd_vlen, &maxcount, eof);
> +	if (nfserr)
> +		return nfserr;
> +
> +	tmp = htonl(NFS4_CONTENT_DATA);
> +	write_bytes_to_xdr_buf(xdr->buf, starting_len,      &tmp,   4);
> +	tmp64 = cpu_to_be64(read->rd_offset);
> +	write_bytes_to_xdr_buf(xdr->buf, starting_len + 4,  &tmp64, 8);
> +	tmp = htonl(maxcount);
> +	write_bytes_to_xdr_buf(xdr->buf, starting_len + 12, &tmp,   4);
> +	return nfs_ok;
> +}
> +
> +static __be32
> +nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> +		       struct nfsd4_read *read)
> +{
> +	unsigned long maxcount;
> +	struct xdr_stream *xdr = &resp->xdr;
> +	struct file *file;
> +	int starting_len = xdr->buf->len;
> +	int segments = 0;
> +	__be32 *p, tmp;
> +	u32 eof;
> +
> +	if (nfserr)
> +		return nfserr;
> +	file = read->rd_nf->nf_file;
> +
> +	/* eof flag, segment count */
> +	p = xdr_reserve_space(xdr, 4 + 4);
> +	if (!p)
> +		return nfserr_resource;
> +	xdr_commit_encode(xdr);
> +
> +	maxcount = svc_max_payload(resp->rqstp);
> +	maxcount = min_t(unsigned long, maxcount,
> +			 (xdr->buf->buflen - xdr->buf->len));
> +	maxcount = min_t(unsigned long, maxcount, read->rd_length);
> +
> +	eof = read->rd_offset >= i_size_read(file_inode(file));
> +	if (!eof) {
> +		nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
> +		segments++;
> +	}
> +
> +	if (nfserr)
> +		xdr_truncate_encode(xdr, starting_len);
> +	else {
> +		tmp = htonl(eof);
> +		write_bytes_to_xdr_buf(xdr->buf, starting_len,     &tmp, 4);
> +		tmp = htonl(segments);
> +		write_bytes_to_xdr_buf(xdr->buf, starting_len + 4, &tmp, 4);
> +	}
>  
>  	return nfserr;
>  }
> @@ -4974,7 +5053,7 @@ static const nfsd4_enc nfsd4_enc_ops[] = {
>  	[OP_LAYOUTSTATS]	= (nfsd4_enc)nfsd4_encode_noop,
>  	[OP_OFFLOAD_CANCEL]	= (nfsd4_enc)nfsd4_encode_noop,
>  	[OP_OFFLOAD_STATUS]	= (nfsd4_enc)nfsd4_encode_offload_status,
> -	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_noop,
> +	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_read_plus,
>  	[OP_SEEK]		= (nfsd4_enc)nfsd4_encode_seek,
>  	[OP_WRITE_SAME]		= (nfsd4_enc)nfsd4_encode_noop,
>  	[OP_CLONE]		= (nfsd4_enc)nfsd4_encode_noop,
> -- 
> 2.28.0
>
Anna Schumaker Sept. 9, 2020, 4:53 p.m. UTC | #2 
On Tue, Sep 8, 2020 at 3:42 PM J. Bruce Fields <bfields@redhat.com> wrote:
>
> On Tue, Sep 08, 2020 at 12:25:56PM -0400, schumaker.anna@gmail.com wrote:
> > From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> >
> > This patch adds READ_PLUS support for returning a single
> > NFS4_CONTENT_DATA segment to the client. This is basically the same as
> > the READ operation, only with the extra information about data segments.
> >
> > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> >
> > ---
> > v5: Fix up nfsd4_read_plus_rsize() calculation
> > ---
> >  fs/nfsd/nfs4proc.c | 20 +++++++++++
> >  fs/nfsd/nfs4xdr.c  | 83 ++++++++++++++++++++++++++++++++++++++++++++--
> >  2 files changed, 101 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > index eaf50eafa935..0a3df5f10501 100644
> > --- a/fs/nfsd/nfs4proc.c
> > +++ b/fs/nfsd/nfs4proc.c
> > @@ -2591,6 +2591,19 @@ static inline u32 nfsd4_read_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> >       return (op_encode_hdr_size + 2 + XDR_QUADLEN(rlen)) * sizeof(__be32);
> >  }
> >
> > +static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > +{
> > +     u32 maxcount = svc_max_payload(rqstp);
> > +     u32 rlen = min(op->u.read.rd_length, maxcount);
> > +     /*
> > +      * Worst case is a single large data segment, so make
> > +      * sure we have enough room to encode that
> > +      */
>
> After the last patch we allow an unlimited number of segments.  So a
> zillion 1-byte segments is also possible, and is a worse case.
>
> Possible ways to avoid that kind of thing:
>
>         - when encoding, stop and return a short read if the xdr-encoded
>           result would exceed the limit calculated here.

Doesn't this happen automatically through calls to xdr_reserve_space()?

>         - round SEEK_HOLE results up to the nearest (say) 512 bytes, and
>           SEEK_DATA result down to the nearest 512 bytes.  May also need
>           some logic to avoid encoding 0-length segments.
>         - talk to linux-fsdevel, see if we can get a minimum hole
>           alignment guarantee from filesystems.
>
> I'm thinking #1 is simplest.
>
> --b.
>
> > +     u32 seg_len = 1 + 2 + 1;
> > +
> > +     return (op_encode_hdr_size + 2 + seg_len + XDR_QUADLEN(rlen)) * sizeof(__be32);
> > +}
> > +
> >  static inline u32 nfsd4_readdir_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> >  {
> >       u32 maxcount = 0, rlen = 0;
> > @@ -3163,6 +3176,13 @@ static const struct nfsd4_operation nfsd4_ops[] = {
> >               .op_name = "OP_COPY",
> >               .op_rsize_bop = nfsd4_copy_rsize,
> >       },
> > +     [OP_READ_PLUS] = {
> > +             .op_func = nfsd4_read,
> > +             .op_release = nfsd4_read_release,
> > +             .op_name = "OP_READ_PLUS",
> > +             .op_rsize_bop = nfsd4_read_plus_rsize,
> > +             .op_get_currentstateid = nfsd4_get_readstateid,
> > +     },
> >       [OP_SEEK] = {
> >               .op_func = nfsd4_seek,
> >               .op_name = "OP_SEEK",
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index 0be194de4888..26d12e3edf33 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -2173,7 +2173,7 @@ static const nfsd4_dec nfsd4_dec_ops[] = {
> >       [OP_LAYOUTSTATS]        = (nfsd4_dec)nfsd4_decode_notsupp,
> >       [OP_OFFLOAD_CANCEL]     = (nfsd4_dec)nfsd4_decode_offload_status,
> >       [OP_OFFLOAD_STATUS]     = (nfsd4_dec)nfsd4_decode_offload_status,
> > -     [OP_READ_PLUS]          = (nfsd4_dec)nfsd4_decode_notsupp,
> > +     [OP_READ_PLUS]          = (nfsd4_dec)nfsd4_decode_read,
> >       [OP_SEEK]               = (nfsd4_dec)nfsd4_decode_seek,
> >       [OP_WRITE_SAME]         = (nfsd4_dec)nfsd4_decode_notsupp,
> >       [OP_CLONE]              = (nfsd4_dec)nfsd4_decode_clone,
> > @@ -4597,6 +4597,85 @@ nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
> >               return nfserr_resource;
> >       p = xdr_encode_hyper(p, os->count);
> >       *p++ = cpu_to_be32(0);
> > +     return nfserr;
> > +}
> > +
> > +static __be32
> > +nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> > +                         struct nfsd4_read *read,
> > +                         unsigned long maxcount,  u32 *eof)
> > +{
> > +     struct xdr_stream *xdr = &resp->xdr;
> > +     struct file *file = read->rd_nf->nf_file;
> > +     int starting_len = xdr->buf->len;
> > +     __be32 nfserr;
> > +     __be32 *p, tmp;
> > +     __be64 tmp64;
> > +
> > +     /* Content type, offset, byte count */
> > +     p = xdr_reserve_space(xdr, 4 + 8 + 4);
> > +     if (!p)
> > +             return nfserr_resource;
> > +
> > +     read->rd_vlen = xdr_reserve_space_vec(xdr, resp->rqstp->rq_vec, maxcount);
> > +     if (read->rd_vlen < 0)
> > +             return nfserr_resource;
> > +
> > +     nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
> > +                         resp->rqstp->rq_vec, read->rd_vlen, &maxcount, eof);
> > +     if (nfserr)
> > +             return nfserr;
> > +
> > +     tmp = htonl(NFS4_CONTENT_DATA);
> > +     write_bytes_to_xdr_buf(xdr->buf, starting_len,      &tmp,   4);
> > +     tmp64 = cpu_to_be64(read->rd_offset);
> > +     write_bytes_to_xdr_buf(xdr->buf, starting_len + 4,  &tmp64, 8);
> > +     tmp = htonl(maxcount);
> > +     write_bytes_to_xdr_buf(xdr->buf, starting_len + 12, &tmp,   4);
> > +     return nfs_ok;
> > +}
> > +
> > +static __be32
> > +nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> > +                    struct nfsd4_read *read)
> > +{
> > +     unsigned long maxcount;
> > +     struct xdr_stream *xdr = &resp->xdr;
> > +     struct file *file;
> > +     int starting_len = xdr->buf->len;
> > +     int segments = 0;
> > +     __be32 *p, tmp;
> > +     u32 eof;
> > +
> > +     if (nfserr)
> > +             return nfserr;
> > +     file = read->rd_nf->nf_file;
> > +
> > +     /* eof flag, segment count */
> > +     p = xdr_reserve_space(xdr, 4 + 4);
> > +     if (!p)
> > +             return nfserr_resource;
> > +     xdr_commit_encode(xdr);
> > +
> > +     maxcount = svc_max_payload(resp->rqstp);
> > +     maxcount = min_t(unsigned long, maxcount,
> > +                      (xdr->buf->buflen - xdr->buf->len));
> > +     maxcount = min_t(unsigned long, maxcount, read->rd_length);
> > +
> > +     eof = read->rd_offset >= i_size_read(file_inode(file));
> > +     if (!eof) {
> > +             nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
> > +             segments++;
> > +     }
> > +
> > +     if (nfserr)
> > +             xdr_truncate_encode(xdr, starting_len);
> > +     else {
> > +             tmp = htonl(eof);
> > +             write_bytes_to_xdr_buf(xdr->buf, starting_len,     &tmp, 4);
> > +             tmp = htonl(segments);
> > +             write_bytes_to_xdr_buf(xdr->buf, starting_len + 4, &tmp, 4);
> > +     }
> >
> >       return nfserr;
> >  }
> > @@ -4974,7 +5053,7 @@ static const nfsd4_enc nfsd4_enc_ops[] = {
> >       [OP_LAYOUTSTATS]        = (nfsd4_enc)nfsd4_encode_noop,
> >       [OP_OFFLOAD_CANCEL]     = (nfsd4_enc)nfsd4_encode_noop,
> >       [OP_OFFLOAD_STATUS]     = (nfsd4_enc)nfsd4_encode_offload_status,
> > -     [OP_READ_PLUS]          = (nfsd4_enc)nfsd4_encode_noop,
> > +     [OP_READ_PLUS]          = (nfsd4_enc)nfsd4_encode_read_plus,
> >       [OP_SEEK]               = (nfsd4_enc)nfsd4_encode_seek,
> >       [OP_WRITE_SAME]         = (nfsd4_enc)nfsd4_encode_noop,
> >       [OP_CLONE]              = (nfsd4_enc)nfsd4_encode_noop,
> > --
> > 2.28.0
> >
>
J. Bruce Fields Sept. 9, 2020, 8:25 p.m. UTC | #3 
On Wed, Sep 09, 2020 at 12:53:18PM -0400, Anna Schumaker wrote:
> On Tue, Sep 8, 2020 at 3:42 PM J. Bruce Fields <bfields@redhat.com> wrote:
> >
> > On Tue, Sep 08, 2020 at 12:25:56PM -0400, schumaker.anna@gmail.com wrote:
> > > From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > >
> > > This patch adds READ_PLUS support for returning a single
> > > NFS4_CONTENT_DATA segment to the client. This is basically the same as
> > > the READ operation, only with the extra information about data segments.
> > >
> > > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > >
> > > ---
> > > v5: Fix up nfsd4_read_plus_rsize() calculation
> > > ---
> > >  fs/nfsd/nfs4proc.c | 20 +++++++++++
> > >  fs/nfsd/nfs4xdr.c  | 83 ++++++++++++++++++++++++++++++++++++++++++++--
> > >  2 files changed, 101 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > > index eaf50eafa935..0a3df5f10501 100644
> > > --- a/fs/nfsd/nfs4proc.c
> > > +++ b/fs/nfsd/nfs4proc.c
> > > @@ -2591,6 +2591,19 @@ static inline u32 nfsd4_read_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > >       return (op_encode_hdr_size + 2 + XDR_QUADLEN(rlen)) * sizeof(__be32);
> > >  }
> > >
> > > +static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > > +{
> > > +     u32 maxcount = svc_max_payload(rqstp);
> > > +     u32 rlen = min(op->u.read.rd_length, maxcount);
> > > +     /*
> > > +      * Worst case is a single large data segment, so make
> > > +      * sure we have enough room to encode that
> > > +      */
> >
> > After the last patch we allow an unlimited number of segments.  So a
> > zillion 1-byte segments is also possible, and is a worse case.
> >
> > Possible ways to avoid that kind of thing:
> >
> >         - when encoding, stop and return a short read if the xdr-encoded
> >           result would exceed the limit calculated here.
> 
> Doesn't this happen automatically through calls to xdr_reserve_space()?

No, xdr_reserve_space() will keep us from running out of buffer
completely, but it won't check that ops come in under the estimates made
in read_plus_rsize().

--b.

> 
> >         - round SEEK_HOLE results up to the nearest (say) 512 bytes, and
> >           SEEK_DATA result down to the nearest 512 bytes.  May also need
> >           some logic to avoid encoding 0-length segments.
> >         - talk to linux-fsdevel, see if we can get a minimum hole
> >           alignment guarantee from filesystems.
> >
> > I'm thinking #1 is simplest.
> >
> > --b.
> >
> > > +     u32 seg_len = 1 + 2 + 1;
> > > +
> > > +     return (op_encode_hdr_size + 2 + seg_len + XDR_QUADLEN(rlen)) * sizeof(__be32);
> > > +}
> > > +
> > >  static inline u32 nfsd4_readdir_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > >  {
> > >       u32 maxcount = 0, rlen = 0;
> > > @@ -3163,6 +3176,13 @@ static const struct nfsd4_operation nfsd4_ops[] = {
> > >               .op_name = "OP_COPY",
> > >               .op_rsize_bop = nfsd4_copy_rsize,
> > >       },
> > > +     [OP_READ_PLUS] = {
> > > +             .op_func = nfsd4_read,
> > > +             .op_release = nfsd4_read_release,
> > > +             .op_name = "OP_READ_PLUS",
> > > +             .op_rsize_bop = nfsd4_read_plus_rsize,
> > > +             .op_get_currentstateid = nfsd4_get_readstateid,
> > > +     },
> > >       [OP_SEEK] = {
> > >               .op_func = nfsd4_seek,
> > >               .op_name = "OP_SEEK",
> > > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > > index 0be194de4888..26d12e3edf33 100644
> > > --- a/fs/nfsd/nfs4xdr.c
> > > +++ b/fs/nfsd/nfs4xdr.c
> > > @@ -2173,7 +2173,7 @@ static const nfsd4_dec nfsd4_dec_ops[] = {
> > >       [OP_LAYOUTSTATS]        = (nfsd4_dec)nfsd4_decode_notsupp,
> > >       [OP_OFFLOAD_CANCEL]     = (nfsd4_dec)nfsd4_decode_offload_status,
> > >       [OP_OFFLOAD_STATUS]     = (nfsd4_dec)nfsd4_decode_offload_status,
> > > -     [OP_READ_PLUS]          = (nfsd4_dec)nfsd4_decode_notsupp,
> > > +     [OP_READ_PLUS]          = (nfsd4_dec)nfsd4_decode_read,
> > >       [OP_SEEK]               = (nfsd4_dec)nfsd4_decode_seek,
> > >       [OP_WRITE_SAME]         = (nfsd4_dec)nfsd4_decode_notsupp,
> > >       [OP_CLONE]              = (nfsd4_dec)nfsd4_decode_clone,
> > > @@ -4597,6 +4597,85 @@ nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
> > >               return nfserr_resource;
> > >       p = xdr_encode_hyper(p, os->count);
> > >       *p++ = cpu_to_be32(0);
> > > +     return nfserr;
> > > +}
> > > +
> > > +static __be32
> > > +nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> > > +                         struct nfsd4_read *read,
> > > +                         unsigned long maxcount,  u32 *eof)
> > > +{
> > > +     struct xdr_stream *xdr = &resp->xdr;
> > > +     struct file *file = read->rd_nf->nf_file;
> > > +     int starting_len = xdr->buf->len;
> > > +     __be32 nfserr;
> > > +     __be32 *p, tmp;
> > > +     __be64 tmp64;
> > > +
> > > +     /* Content type, offset, byte count */
> > > +     p = xdr_reserve_space(xdr, 4 + 8 + 4);
> > > +     if (!p)
> > > +             return nfserr_resource;
> > > +
> > > +     read->rd_vlen = xdr_reserve_space_vec(xdr, resp->rqstp->rq_vec, maxcount);
> > > +     if (read->rd_vlen < 0)
> > > +             return nfserr_resource;
> > > +
> > > +     nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
> > > +                         resp->rqstp->rq_vec, read->rd_vlen, &maxcount, eof);
> > > +     if (nfserr)
> > > +             return nfserr;
> > > +
> > > +     tmp = htonl(NFS4_CONTENT_DATA);
> > > +     write_bytes_to_xdr_buf(xdr->buf, starting_len,      &tmp,   4);
> > > +     tmp64 = cpu_to_be64(read->rd_offset);
> > > +     write_bytes_to_xdr_buf(xdr->buf, starting_len + 4,  &tmp64, 8);
> > > +     tmp = htonl(maxcount);
> > > +     write_bytes_to_xdr_buf(xdr->buf, starting_len + 12, &tmp,   4);
> > > +     return nfs_ok;
> > > +}
> > > +
> > > +static __be32
> > > +nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> > > +                    struct nfsd4_read *read)
> > > +{
> > > +     unsigned long maxcount;
> > > +     struct xdr_stream *xdr = &resp->xdr;
> > > +     struct file *file;
> > > +     int starting_len = xdr->buf->len;
> > > +     int segments = 0;
> > > +     __be32 *p, tmp;
> > > +     u32 eof;
> > > +
> > > +     if (nfserr)
> > > +             return nfserr;
> > > +     file = read->rd_nf->nf_file;
> > > +
> > > +     /* eof flag, segment count */
> > > +     p = xdr_reserve_space(xdr, 4 + 4);
> > > +     if (!p)
> > > +             return nfserr_resource;
> > > +     xdr_commit_encode(xdr);
> > > +
> > > +     maxcount = svc_max_payload(resp->rqstp);
> > > +     maxcount = min_t(unsigned long, maxcount,
> > > +                      (xdr->buf->buflen - xdr->buf->len));
> > > +     maxcount = min_t(unsigned long, maxcount, read->rd_length);
> > > +
> > > +     eof = read->rd_offset >= i_size_read(file_inode(file));
> > > +     if (!eof) {
> > > +             nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
> > > +             segments++;
> > > +     }
> > > +
> > > +     if (nfserr)
> > > +             xdr_truncate_encode(xdr, starting_len);
> > > +     else {
> > > +             tmp = htonl(eof);
> > > +             write_bytes_to_xdr_buf(xdr->buf, starting_len,     &tmp, 4);
> > > +             tmp = htonl(segments);
> > > +             write_bytes_to_xdr_buf(xdr->buf, starting_len + 4, &tmp, 4);
> > > +     }
> > >
> > >       return nfserr;
> > >  }
> > > @@ -4974,7 +5053,7 @@ static const nfsd4_enc nfsd4_enc_ops[] = {
> > >       [OP_LAYOUTSTATS]        = (nfsd4_enc)nfsd4_encode_noop,
> > >       [OP_OFFLOAD_CANCEL]     = (nfsd4_enc)nfsd4_encode_noop,
> > >       [OP_OFFLOAD_STATUS]     = (nfsd4_enc)nfsd4_encode_offload_status,
> > > -     [OP_READ_PLUS]          = (nfsd4_enc)nfsd4_encode_noop,
> > > +     [OP_READ_PLUS]          = (nfsd4_enc)nfsd4_encode_read_plus,
> > >       [OP_SEEK]               = (nfsd4_enc)nfsd4_encode_seek,
> > >       [OP_WRITE_SAME]         = (nfsd4_enc)nfsd4_encode_noop,
> > >       [OP_CLONE]              = (nfsd4_enc)nfsd4_encode_noop,
> > > --
> > > 2.28.0
> > >
> >
J. Bruce Fields Sept. 9, 2020, 8:50 p.m. UTC | #4 
On Wed, Sep 09, 2020 at 04:25:34PM -0400, bfields wrote:
> On Wed, Sep 09, 2020 at 12:53:18PM -0400, Anna Schumaker wrote:
> > On Tue, Sep 8, 2020 at 3:42 PM J. Bruce Fields <bfields@redhat.com> wrote:
> > >
> > > On Tue, Sep 08, 2020 at 12:25:56PM -0400, schumaker.anna@gmail.com wrote:
> > > > From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > > >
> > > > This patch adds READ_PLUS support for returning a single
> > > > NFS4_CONTENT_DATA segment to the client. This is basically the same as
> > > > the READ operation, only with the extra information about data segments.
> > > >
> > > > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > > >
> > > > ---
> > > > v5: Fix up nfsd4_read_plus_rsize() calculation
> > > > ---
> > > >  fs/nfsd/nfs4proc.c | 20 +++++++++++
> > > >  fs/nfsd/nfs4xdr.c  | 83 ++++++++++++++++++++++++++++++++++++++++++++--
> > > >  2 files changed, 101 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > > > index eaf50eafa935..0a3df5f10501 100644
> > > > --- a/fs/nfsd/nfs4proc.c
> > > > +++ b/fs/nfsd/nfs4proc.c
> > > > @@ -2591,6 +2591,19 @@ static inline u32 nfsd4_read_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > > >       return (op_encode_hdr_size + 2 + XDR_QUADLEN(rlen)) * sizeof(__be32);
> > > >  }
> > > >
> > > > +static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > > > +{
> > > > +     u32 maxcount = svc_max_payload(rqstp);
> > > > +     u32 rlen = min(op->u.read.rd_length, maxcount);
> > > > +     /*
> > > > +      * Worst case is a single large data segment, so make
> > > > +      * sure we have enough room to encode that
> > > > +      */
> > >
> > > After the last patch we allow an unlimited number of segments.  So a
> > > zillion 1-byte segments is also possible, and is a worse case.
> > >
> > > Possible ways to avoid that kind of thing:
> > >
> > >         - when encoding, stop and return a short read if the xdr-encoded
> > >           result would exceed the limit calculated here.
> > 
> > Doesn't this happen automatically through calls to xdr_reserve_space()?
> 
> No, xdr_reserve_space() will keep us from running out of buffer
> completely, but it won't check that ops come in under the estimates made
> in read_plus_rsize().

If it's easier, another option might be just: if we ever get a "small"
hole (say, less than 512 bytes), just give up and encode the rest of the
result as a single big data segment.

--b.
diff mbox series

Patch

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index eaf50eafa935..0a3df5f10501 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2591,6 +2591,19 @@  static inline u32 nfsd4_read_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 	return (op_encode_hdr_size + 2 + XDR_QUADLEN(rlen)) * sizeof(__be32);
 }
 
+static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	u32 maxcount = svc_max_payload(rqstp);
+	u32 rlen = min(op->u.read.rd_length, maxcount);
+	/*
+	 * Worst case is a single large data segment, so make
+	 * sure we have enough room to encode that
+	 */
+	u32 seg_len = 1 + 2 + 1;
+
+	return (op_encode_hdr_size + 2 + seg_len + XDR_QUADLEN(rlen)) * sizeof(__be32);
+}
+
 static inline u32 nfsd4_readdir_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	u32 maxcount = 0, rlen = 0;
@@ -3163,6 +3176,13 @@  static const struct nfsd4_operation nfsd4_ops[] = {
 		.op_name = "OP_COPY",
 		.op_rsize_bop = nfsd4_copy_rsize,
 	},
+	[OP_READ_PLUS] = {
+		.op_func = nfsd4_read,
+		.op_release = nfsd4_read_release,
+		.op_name = "OP_READ_PLUS",
+		.op_rsize_bop = nfsd4_read_plus_rsize,
+		.op_get_currentstateid = nfsd4_get_readstateid,
+	},
 	[OP_SEEK] = {
 		.op_func = nfsd4_seek,
 		.op_name = "OP_SEEK",
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 0be194de4888..26d12e3edf33 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2173,7 +2173,7 @@  static const nfsd4_dec nfsd4_dec_ops[] = {
 	[OP_LAYOUTSTATS]	= (nfsd4_dec)nfsd4_decode_notsupp,
 	[OP_OFFLOAD_CANCEL]	= (nfsd4_dec)nfsd4_decode_offload_status,
 	[OP_OFFLOAD_STATUS]	= (nfsd4_dec)nfsd4_decode_offload_status,
-	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_notsupp,
+	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_read,
 	[OP_SEEK]		= (nfsd4_dec)nfsd4_decode_seek,
 	[OP_WRITE_SAME]		= (nfsd4_dec)nfsd4_decode_notsupp,
 	[OP_CLONE]		= (nfsd4_dec)nfsd4_decode_clone,
@@ -4597,6 +4597,85 @@  nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
 		return nfserr_resource;
 	p = xdr_encode_hyper(p, os->count);
 	*p++ = cpu_to_be32(0);
+	return nfserr;
+}
+
+static __be32
+nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
+			    struct nfsd4_read *read,
+			    unsigned long maxcount,  u32 *eof)
+{
+	struct xdr_stream *xdr = &resp->xdr;
+	struct file *file = read->rd_nf->nf_file;
+	int starting_len = xdr->buf->len;
+	__be32 nfserr;
+	__be32 *p, tmp;
+	__be64 tmp64;
+
+	/* Content type, offset, byte count */
+	p = xdr_reserve_space(xdr, 4 + 8 + 4);
+	if (!p)
+		return nfserr_resource;
+
+	read->rd_vlen = xdr_reserve_space_vec(xdr, resp->rqstp->rq_vec, maxcount);
+	if (read->rd_vlen < 0)
+		return nfserr_resource;
+
+	nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
+			    resp->rqstp->rq_vec, read->rd_vlen, &maxcount, eof);
+	if (nfserr)
+		return nfserr;
+
+	tmp = htonl(NFS4_CONTENT_DATA);
+	write_bytes_to_xdr_buf(xdr->buf, starting_len,      &tmp,   4);
+	tmp64 = cpu_to_be64(read->rd_offset);
+	write_bytes_to_xdr_buf(xdr->buf, starting_len + 4,  &tmp64, 8);
+	tmp = htonl(maxcount);
+	write_bytes_to_xdr_buf(xdr->buf, starting_len + 12, &tmp,   4);
+	return nfs_ok;
+}
+
+static __be32
+nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
+		       struct nfsd4_read *read)
+{
+	unsigned long maxcount;
+	struct xdr_stream *xdr = &resp->xdr;
+	struct file *file;
+	int starting_len = xdr->buf->len;
+	int segments = 0;
+	__be32 *p, tmp;
+	u32 eof;
+
+	if (nfserr)
+		return nfserr;
+	file = read->rd_nf->nf_file;
+
+	/* eof flag, segment count */
+	p = xdr_reserve_space(xdr, 4 + 4);
+	if (!p)
+		return nfserr_resource;
+	xdr_commit_encode(xdr);
+
+	maxcount = svc_max_payload(resp->rqstp);
+	maxcount = min_t(unsigned long, maxcount,
+			 (xdr->buf->buflen - xdr->buf->len));
+	maxcount = min_t(unsigned long, maxcount, read->rd_length);
+
+	eof = read->rd_offset >= i_size_read(file_inode(file));
+	if (!eof) {
+		nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
+		segments++;
+	}
+
+	if (nfserr)
+		xdr_truncate_encode(xdr, starting_len);
+	else {
+		tmp = htonl(eof);
+		write_bytes_to_xdr_buf(xdr->buf, starting_len,     &tmp, 4);
+		tmp = htonl(segments);
+		write_bytes_to_xdr_buf(xdr->buf, starting_len + 4, &tmp, 4);
+	}
 
 	return nfserr;
 }
@@ -4974,7 +5053,7 @@  static const nfsd4_enc nfsd4_enc_ops[] = {
 	[OP_LAYOUTSTATS]	= (nfsd4_enc)nfsd4_encode_noop,
 	[OP_OFFLOAD_CANCEL]	= (nfsd4_enc)nfsd4_encode_noop,
 	[OP_OFFLOAD_STATUS]	= (nfsd4_enc)nfsd4_encode_offload_status,
-	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_noop,
+	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_read_plus,
 	[OP_SEEK]		= (nfsd4_enc)nfsd4_encode_seek,
 	[OP_WRITE_SAME]		= (nfsd4_enc)nfsd4_encode_noop,
 	[OP_CLONE]		= (nfsd4_enc)nfsd4_encode_noop,