On Fri, Aug 28, 2020 at 5:56 PM J. Bruce Fields <bfields@xxxxxxxxxx> wrote:
>
> On Fri, Aug 28, 2020 at 05:25:21PM -0400, J. Bruce Fields wrote:
> > On Mon, Aug 17, 2020 at 12:53:07PM -0400, schumaker.anna@xxxxxxxxx wrote:
> > > From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxx>
> > > ---
> > > fs/nfsd/nfs4proc.c | 17 ++++++++++
> > > fs/nfsd/nfs4xdr.c | 83 ++++++++++++++++++++++++++++++++++++++++++++--
> > > 2 files changed, 98 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > > index a09c35f0f6f0..9630d33211f2 100644
> > > --- a/fs/nfsd/nfs4proc.c
> > > +++ b/fs/nfsd/nfs4proc.c
> > > @@ -2523,6 +2523,16 @@ 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);
> > > + /* enough extra xdr space for encoding either a hole or data segment. */
> > > + u32 segments = 1 + 2 + 2;
> > > +
> > > + return (op_encode_hdr_size + 2 + segments + XDR_QUADLEN(rlen)) * sizeof(__be32);
> >
> > I'm not sure I understand this calculation.
> >
> > In the final code, there's no fixed limit on the number of segments
> > returned by a single READ_PLUS op, right?
>
> I think the worst-case overhead to represent a hole is around 50 bytes.
>
> So as long as we don't encode any holes less than that, then we can just
> use rlen as an upper bound.
>
> We really don't want to bother encoding small holes. I doubt
> filesystems want to bother with them either. Do they give us any
> guarantees as to the minimum size of a hole?
The minimum size seems to be PAGE_SIZE from everything I've seen.
>
> --b.
>
> >
> > --b.
> >
> > > +}
> > > +
> > > static inline u32 nfsd4_readdir_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
> > > {
> > > u32 maxcount = 0, rlen = 0;
> > > @@ -3059,6 +3069,13 @@ 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 6a1c0a7fae05..9af92f538000 100644
> > > --- a/fs/nfsd/nfs4xdr.c
> > > +++ b/fs/nfsd/nfs4xdr.c
> > > @@ -1957,7 +1957,7 @@ 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,
> > > @@ -4367,6 +4367,85 @@ 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;
> > > }
> > > @@ -4509,7 +4588,7 @@ 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
> > >
>
