On Tue, Sep 08, 2020 at 12:25:58PM -0400, schumaker.anna@xxxxxxxxx wrote:
> From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
>
> But only one of each right now. We'll expand on this in the next patch.
>
> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> ---
> v5: If we've already encoded a segment, then return a short read if
> later segments return an error for some reason.
> ---
> fs/nfsd/nfs4xdr.c | 54 ++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 39 insertions(+), 15 deletions(-)
>
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 45159bd9e9a4..856606263c1d 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -4603,7 +4603,7 @@ nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
> static __be32
> nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> struct nfsd4_read *read,
> - unsigned long maxcount, u32 *eof)
> + unsigned long *maxcount, u32 *eof)
> {
> struct xdr_stream *xdr = &resp->xdr;
> struct file *file = read->rd_nf->nf_file;
> @@ -4614,19 +4614,19 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> __be64 tmp64;
>
> if (hole_pos > read->rd_offset)
> - maxcount = min_t(unsigned long, maxcount, hole_pos - read->rd_offset);
> + *maxcount = min_t(unsigned long, *maxcount, hole_pos - read->rd_offset);
>
> /* 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);
> + 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);
> + resp->rqstp->rq_vec, read->rd_vlen, maxcount, eof);
> if (nfserr)
> return nfserr;
>
> @@ -4634,7 +4634,7 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> 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);
> + tmp = htonl(*maxcount);
> write_bytes_to_xdr_buf(xdr->buf, starting_len + 12, &tmp, 4);
> return nfs_ok;
> }
> @@ -4642,11 +4642,19 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
> static __be32
> nfsd4_encode_read_plus_hole(struct nfsd4_compoundres *resp,
> struct nfsd4_read *read,
> - unsigned long maxcount, u32 *eof)
> + unsigned long *maxcount, u32 *eof)
> {
> struct file *file = read->rd_nf->nf_file;
> + loff_t data_pos = vfs_llseek(file, read->rd_offset, SEEK_DATA);
> + unsigned long count;
> __be32 *p;
>
> + if (data_pos == -ENXIO)
> + data_pos = i_size_read(file_inode(file));
> + else if (data_pos <= read->rd_offset)
> + return nfserr_resource;
I think there's still a race here:
vfs_llseek(.,0,SEEK_HOLE) returns 1024
read 1024 bytes of data
another process fills the hole
vfs_llseek(.,1024,SEEK_DATA) returns 1024
code above returns nfserr_resource
We end up returning an error to the client when we should have just
returned more data.
--b.
> + count = data_pos - read->rd_offset;
> +
> /* Content type, offset, byte count */
> p = xdr_reserve_space(&resp->xdr, 4 + 8 + 8);
> if (!p)
> @@ -4654,9 +4662,10 @@ nfsd4_encode_read_plus_hole(struct nfsd4_compoundres *resp,
>
> *p++ = htonl(NFS4_CONTENT_HOLE);
> p = xdr_encode_hyper(p, read->rd_offset);
> - p = xdr_encode_hyper(p, maxcount);
> + p = xdr_encode_hyper(p, count);
>
> - *eof = (read->rd_offset + maxcount) >= i_size_read(file_inode(file));
> + *eof = (read->rd_offset + count) >= i_size_read(file_inode(file));
> + *maxcount = min_t(unsigned long, count, *maxcount);
> return nfs_ok;
> }
>
> @@ -4664,7 +4673,7 @@ static __be32
> nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> struct nfsd4_read *read)
> {
> - unsigned long maxcount;
> + unsigned long maxcount, count;
> struct xdr_stream *xdr = &resp->xdr;
> struct file *file;
> int starting_len = xdr->buf->len;
> @@ -4687,6 +4696,7 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> maxcount = min_t(unsigned long, maxcount,
> (xdr->buf->buflen - xdr->buf->len));
> maxcount = min_t(unsigned long, maxcount, read->rd_length);
> + count = maxcount;
>
> eof = read->rd_offset >= i_size_read(file_inode(file));
> if (eof)
> @@ -4695,24 +4705,38 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
> pos = vfs_llseek(file, read->rd_offset, SEEK_DATA);
> if (pos == -ENXIO)
> pos = i_size_read(file_inode(file));
> + else if (pos < 0)
> + pos = read->rd_offset;
>
> - if (pos > read->rd_offset) {
> - maxcount = pos - read->rd_offset;
> - nfserr = nfsd4_encode_read_plus_hole(resp, read, maxcount, &eof);
> + if (pos == read->rd_offset) {
> + maxcount = count;
> + nfserr = nfsd4_encode_read_plus_data(resp, read, &maxcount, &eof);
> + if (nfserr)
> + goto out;
> + count -= maxcount;
> + read->rd_offset += maxcount;
> segments++;
> - } else {
> - nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
> + }
> +
> + if (count > 0 && !eof) {
> + maxcount = count;
> + nfserr = nfsd4_encode_read_plus_hole(resp, read, &maxcount, &eof);
> + if (nfserr)
> + goto out;
> + count -= maxcount;
> + read->rd_offset += maxcount;
> segments++;
> }
>
> out:
> - if (nfserr)
> + if (nfserr && segments == 0)
> 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);
> + nfserr = nfs_ok;
> }
>
> return nfserr;
> --
> 2.28.0
>
