On Mon, Mar 16, 2015 at 05:18:08PM -0400, Anna Schumaker wrote:
> This patch implements sending an array of segments back to the client.
> Clients should be prepared to handle multiple segment reads to make this
> useful. We try to splice the first data segment into the XDR result,
> and remaining segments are encoded directly.
I'm still interested in what would happen if we started with an
implementation like:
- if the entire requested range falls within a hole, return that
single hole.
- otherwise, just treat the thing as one big data segment.
That would provide a benefit in the case there are large-ish holes
with minimal impact otherwise.
(Though patches for full support are still useful even if only for
client-testing purposes.)
--b.
>
> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4proc.c | 4 ++--
> fs/nfsd/nfs4xdr.c | 35 ++++++++++++++++++++++++-----------
> 2 files changed, 26 insertions(+), 13 deletions(-)
>
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index e9f4d8f..6801973 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1862,8 +1862,8 @@ static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_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 xdr = 5;
> + /* Extra xdr padding for encoding multiple segments. */
> + u32 xdr = 20;
>
> return (op_encode_hdr_size + 2 + xdr + XDR_QUADLEN(rlen)) * sizeof(__be32);
> }
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 799d52c..5eaecd2 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -4117,7 +4117,7 @@ nfsd4_encode_layoutreturn(struct nfsd4_compoundres *resp, __be32 nfserr,
>
> static __be32
> nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp, struct nfsd4_read *read,
> - struct file *file)
> + struct file *file, loff_t hole_pos)
> {
> __be32 *p, err;
> unsigned long maxcount;
> @@ -4128,20 +4128,26 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp, struct nfsd4_read *r
> return nfserr_resource;
> xdr_commit_encode(xdr);
>
> + if (hole_pos <= read->rd_offset)
> + hole_pos = i_size_read(file_inode(file));
> +
> 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);
> + maxcount = min_t(unsigned long, maxcount, hole_pos - read->rd_offset);
>
> if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags))
> err = nfsd4_encode_splice_read(resp, read, file, &maxcount);
> else
> err = nfsd4_encode_readv(resp, read, file, &maxcount);
> + clear_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags);
>
> *p++ = cpu_to_be32(NFS4_CONTENT_DATA);
> p = xdr_encode_hyper(p, read->rd_offset);
> *p++ = cpu_to_be32(maxcount);
>
> read->rd_offset += maxcount;
> + read->rd_length -= maxcount;
> return err;
> }
>
> @@ -4156,7 +4162,7 @@ nfsd4_encode_read_plus_hole(struct nfsd4_compoundres *resp, struct nfsd4_read *r
> if (data_pos == -ENXIO)
> data_pos = i_size_read(file_inode(file));
> if (data_pos <= read->rd_offset)
> - return nfsd4_encode_read_plus_data(resp, read, file);
> + return nfsd4_encode_read_plus_data(resp, read, file, 0);
>
> maxcount = data_pos - read->rd_offset;
> p = xdr_reserve_space(&resp->xdr, 4 + 8 + 8);
> @@ -4165,6 +4171,10 @@ nfsd4_encode_read_plus_hole(struct nfsd4_compoundres *resp, struct nfsd4_read *r
> p = xdr_encode_hyper(p, maxcount);
>
> read->rd_offset += maxcount;
> + if (maxcount > read->rd_length)
> + read->rd_length = 0;
> + else
> + read->rd_length -= maxcount;
> return nfs_ok;
> }
>
> @@ -4197,17 +4207,20 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> goto err_truncate;
> }
>
> - hole_pos = vfs_llseek(file, read->rd_offset, SEEK_HOLE);
> - if (hole_pos == -ENXIO)
> - goto out_encode;
> + do {
> + hole_pos = vfs_llseek(file, read->rd_offset, SEEK_HOLE);
> + if (hole_pos == -ENXIO)
> + break;
>
> - if (hole_pos == read->rd_offset)
> - err = nfsd4_encode_read_plus_hole(resp, read, file);
> - else
> - err = nfsd4_encode_read_plus_data(resp, read, file);
> - segments++;
> + if (hole_pos == read->rd_offset)
> + err = nfsd4_encode_read_plus_hole(resp, read, file);
> + else
> + err = nfsd4_encode_read_plus_data(resp, read, file, hole_pos);
> + if (err)
> + break;
> + segments++;
> + } while (read->rd_length > 0);
>
> -out_encode:
> eof = (read->rd_offset >= i_size_read(file_inode(file)));
> *p++ = cpu_to_be32(eof);
> *p++ = cpu_to_be32(segments);
> --
> 2.3.3
>
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