On Tue, Aug 31, 2021 at 09:19:23PM +0000, Chuck Lever III wrote:
>
> > On Aug 31, 2021, at 4:40 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> >
> > How does this deal with compounds with multiple writes?
>
> Explained in the cover letter.
Whoops, I see now, thanks.--b.
>
>
> > We don't need to handle those efficiently, but we do need to handle
> > them.
> >
> > --b.
> >
> > On Tue, Aug 31, 2021 at 03:05:46PM -0400, Chuck Lever wrote:
> >> This enables the XDR decoder to figure out how the payload sink
> >> buffer needs to be aligned before setting up the RDMA Reads.
> >> Then re-alignment of large RDMA Read payloads can be avoided.
> >>
> >> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >> ---
> >> include/linux/sunrpc/svc_rdma.h | 6 +
> >> include/trace/events/rpcrdma.h | 26 ++++++
> >> net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 17 +++-
> >> net/sunrpc/xprtrdma/svc_rdma_rw.c | 139 ++++++++++++++++++++++++++++---
> >> 4 files changed, 169 insertions(+), 19 deletions(-)
> >>
> >> diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
> >> index f660244cc8ba..8d80a759a909 100644
> >> --- a/include/linux/sunrpc/svc_rdma.h
> >> +++ b/include/linux/sunrpc/svc_rdma.h
> >> @@ -192,6 +192,12 @@ extern int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
> >> extern int svc_rdma_process_read_list(struct svcxprt_rdma *rdma,
> >> struct svc_rqst *rqstp,
> >> struct svc_rdma_recv_ctxt *head);
> >> +extern void svc_rdma_prepare_read_chunk(struct svc_rqst *rqstp,
> >> + struct svc_rdma_recv_ctxt *head);
> >> +extern int svc_rdma_pull_read_chunk(struct svcxprt_rdma *rdma,
> >> + struct svc_rqst *rqstp,
> >> + struct svc_rdma_recv_ctxt *ctxt,
> >> + unsigned int offset, unsigned int length);
> >>
> >> /* svc_rdma_sendto.c */
> >> extern void svc_rdma_send_ctxts_destroy(struct svcxprt_rdma *rdma);
> >> diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
> >> index 5954ce036173..30440cca321a 100644
> >> --- a/include/trace/events/rpcrdma.h
> >> +++ b/include/trace/events/rpcrdma.h
> >> @@ -2136,6 +2136,32 @@ TRACE_EVENT(svcrdma_sq_post_err,
> >> )
> >> );
> >>
> >> +TRACE_EVENT(svcrdma_arg_payload,
> >> + TP_PROTO(
> >> + const struct svc_rqst *rqstp,
> >> + unsigned int offset,
> >> + unsigned int length
> >> + ),
> >> +
> >> + TP_ARGS(rqstp, offset, length),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, xid)
> >> + __field(u32, offset)
> >> + __field(u32, length)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->xid = __be32_to_cpu(rqstp->rq_xid);
> >> + __entry->offset = offset_in_page(offset);
> >> + __entry->length = length;
> >> + ),
> >> +
> >> + TP_printk("xid=0x%08x offset=%u length=%u",
> >> + __entry->xid, __entry->offset, __entry->length
> >> + )
> >> +);
> >> +
> >> #endif /* _TRACE_RPCRDMA_H */
> >>
> >> #include <trace/define_trace.h>
> >> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> >> index 08a620b370ae..cd9c0fb1a470 100644
> >> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> >> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> >> @@ -838,12 +838,13 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
> >>
> >> svc_rdma_get_inv_rkey(rdma_xprt, ctxt);
> >>
> >> - if (!pcl_is_empty(&ctxt->rc_read_pcl) ||
> >> - !pcl_is_empty(&ctxt->rc_call_pcl)) {
> >> + if (!pcl_is_empty(&ctxt->rc_call_pcl) ||
> >> + ctxt->rc_read_pcl.cl_count > 1) {
> >> ret = svc_rdma_process_read_list(rdma_xprt, rqstp, ctxt);
> >> if (ret < 0)
> >> goto out_readfail;
> >> - }
> >> + } else if (ctxt->rc_read_pcl.cl_count == 1)
> >> + svc_rdma_prepare_read_chunk(rqstp, ctxt);
> >>
> >> rqstp->rq_xprt_ctxt = ctxt;
> >> rqstp->rq_prot = IPPROTO_MAX;
> >> @@ -887,5 +888,13 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
> >> int svc_rdma_argument_payload(struct svc_rqst *rqstp, unsigned int offset,
> >> unsigned int length)
> >> {
> >> - return 0;
> >> + struct svc_rdma_recv_ctxt *ctxt = rqstp->rq_xprt_ctxt;
> >> + struct svc_xprt *xprt = rqstp->rq_xprt;
> >> + struct svcxprt_rdma *rdma =
> >> + container_of(xprt, struct svcxprt_rdma, sc_xprt);
> >> +
> >> + if (!pcl_is_empty(&ctxt->rc_call_pcl) ||
> >> + ctxt->rc_read_pcl.cl_count != 1)
> >> + return 0;
> >> + return svc_rdma_pull_read_chunk(rdma, rqstp, ctxt, offset, length);
> >> }
> >> diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> >> index 29b7d477891c..5f03dfd2fa03 100644
> >> --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
> >> +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> >> @@ -707,19 +707,24 @@ static int svc_rdma_build_read_segment(struct svc_rdma_read_info *info,
> >>
> >> len = segment->rs_length;
> >> sge_no = PAGE_ALIGN(info->ri_pageoff + len) >> PAGE_SHIFT;
> >> +
> >> + trace_printk("pageoff=%u len=%u sges=%u\n",
> >> + info->ri_pageoff, len, sge_no);
> >> +
> >> ctxt = svc_rdma_get_rw_ctxt(cc->cc_rdma, sge_no);
> >> if (!ctxt)
> >> return -ENOMEM;
> >> ctxt->rw_nents = sge_no;
> >> + head->rc_page_count += sge_no;
> >>
> >> sg = ctxt->rw_sg_table.sgl;
> >> for (sge_no = 0; sge_no < ctxt->rw_nents; sge_no++) {
> >> seg_len = min_t(unsigned int, len,
> >> PAGE_SIZE - info->ri_pageoff);
> >>
> >> - if (!info->ri_pageoff)
> >> - head->rc_page_count++;
> >> -
> >> + trace_printk(" page=%p seg_len=%u offset=%u\n",
> >> + rqstp->rq_pages[info->ri_pageno], seg_len,
> >> + info->ri_pageoff);
> >> sg_set_page(sg, rqstp->rq_pages[info->ri_pageno],
> >> seg_len, info->ri_pageoff);
> >> sg = sg_next(sg);
> >> @@ -804,15 +809,14 @@ static int svc_rdma_copy_inline_range(struct svc_rdma_read_info *info,
> >> unsigned int page_no, numpages;
> >>
> >> numpages = PAGE_ALIGN(info->ri_pageoff + remaining) >> PAGE_SHIFT;
> >> + head->rc_page_count += numpages;
> >> +
> >> for (page_no = 0; page_no < numpages; page_no++) {
> >> unsigned int page_len;
> >>
> >> page_len = min_t(unsigned int, remaining,
> >> PAGE_SIZE - info->ri_pageoff);
> >>
> >> - if (!info->ri_pageoff)
> >> - head->rc_page_count++;
> >> -
> >> dst = page_address(rqstp->rq_pages[info->ri_pageno]);
> >> memcpy(dst + info->ri_pageno, src + offset, page_len);
> >>
> >> @@ -1092,15 +1096,8 @@ static noinline int svc_rdma_read_special(struct svc_rdma_read_info *info)
> >> * @rqstp: set of pages to use as Read sink buffers
> >> * @head: pages under I/O collect here
> >> *
> >> - * The RPC/RDMA protocol assumes that the upper layer's XDR decoders
> >> - * pull each Read chunk as they decode an incoming RPC message.
> >> - *
> >> - * On Linux, however, the server needs to have a fully-constructed RPC
> >> - * message in rqstp->rq_arg when there is a positive return code from
> >> - * ->xpo_recvfrom. So the Read list is safety-checked immediately when
> >> - * it is received, then here the whole Read list is pulled all at once.
> >> - * The ingress RPC message is fully reconstructed once all associated
> >> - * RDMA Reads have completed.
> >> + * Handle complex Read chunk cases fully before svc_rdma_recvfrom()
> >> + * returns.
> >> *
> >> * Return values:
> >> * %1: all needed RDMA Reads were posted successfully,
> >> @@ -1159,3 +1156,115 @@ int svc_rdma_process_read_list(struct svcxprt_rdma *rdma,
> >> svc_rdma_read_info_free(info);
> >> return ret;
> >> }
> >> +
> >> +/**
> >> + * svc_rdma_prepare_read_chunk - Prepare rq_arg for Read chunk
> >> + * @rqstp: set of pages to use as Read sink buffers
> >> + * @head: pages under I/O collect here
> >> + *
> >> + * The Read chunk will be pulled when the upper layer's XDR
> >> + * decoder calls svc_decode_argument_payload(). In the meantime,
> >> + * fake up rq_arg.page_len and .len to reflect the size of the
> >> + * yet-to-be-pulled payload.
> >> + */
> >> +void svc_rdma_prepare_read_chunk(struct svc_rqst *rqstp,
> >> + struct svc_rdma_recv_ctxt *head)
> >> +{
> >> + struct svc_rdma_chunk *chunk = pcl_first_chunk(&head->rc_read_pcl);
> >> + unsigned int length = xdr_align_size(chunk->ch_length);
> >> + struct xdr_buf *buf = &rqstp->rq_arg;
> >> +
> >> + buf->tail[0].iov_base = buf->head[0].iov_base + chunk->ch_position;
> >> + buf->tail[0].iov_len = buf->head[0].iov_len - chunk->ch_position;
> >> + buf->head[0].iov_len = chunk->ch_position;
> >> +
> >> + buf->page_len = length;
> >> + buf->len += length;
> >> + buf->buflen += length;
> >> +
> >> + /*
> >> + * rq_respages starts after the last arg page. Note that we
> >> + * don't know the offset yet, so add an extra page as slack.
> >> + */
> >> + length += PAGE_SIZE * 2 - 1;
> >> + rqstp->rq_respages = &rqstp->rq_pages[length >> PAGE_SHIFT];
> >> + rqstp->rq_next_page = rqstp->rq_respages + 1;
> >> +}
> >> +
> >> +/**
> >> + * svc_rdma_pull_read_chunk - Pull one Read chunk from the client
> >> + * @rdma: controlling RDMA transport
> >> + * @rqstp: set of pages to use as Read sink buffers
> >> + * @head: pages under I/O collect here
> >> + * @offset: offset of payload in file's page cache
> >> + * @length: size of payload, in bytes
> >> + *
> >> + * Once the upper layer's XDR decoder has decoded the length of
> >> + * the payload and it's offset, we can be clever about setting up
> >> + * the RDMA Read sink buffer so that the VFS does not have to
> >> + * re-align the payload once it is received.
> >> + *
> >> + * Caveat: To keep things simple, this is an optimization that is
> >> + * used only when there is a single Read chunk in the Read
> >> + * list.
> >> + *
> >> + * Return values:
> >> + * %0: all needed RDMA Reads were posted successfully,
> >> + * %-EINVAL: client provided the wrong chunk size,
> >> + * %-ENOMEM: rdma_rw context pool was exhausted,
> >> + * %-ENOTCONN: posting failed (connection is lost),
> >> + * %-EIO: rdma_rw initialization failed (DMA mapping, etc).
> >> + */
> >> +int svc_rdma_pull_read_chunk(struct svcxprt_rdma *rdma, struct svc_rqst *rqstp,
> >> + struct svc_rdma_recv_ctxt *head,
> >> + unsigned int offset, unsigned int length)
> >> +{
> >> + struct svc_rdma_read_info *info;
> >> + struct svc_rdma_chunk_ctxt *cc;
> >> + struct svc_rdma_chunk *chunk;
> >> + int ret;
> >> +
> >> + trace_svcrdma_arg_payload(rqstp, offset, length);
> >> +
> >> + /* Sanity: the Requester must have provided enough
> >> + * bytes to fill the XDR opaque.
> >> + */
> >> + chunk = pcl_first_chunk(&head->rc_read_pcl);
> >> + if (length > chunk->ch_length)
> >> + return -EINVAL;
> >> +
> >> + info = svc_rdma_read_info_alloc(rdma);
> >> + if (!info)
> >> + return -ENOMEM;
> >> + cc = &info->ri_cc;
> >> + info->ri_rqst = rqstp;
> >> + info->ri_readctxt = head;
> >> + info->ri_pageno = 0;
> >> + info->ri_pageoff = offset_in_page(offset);
> >> + info->ri_totalbytes = 0;
> >> +
> >> + ret = svc_rdma_build_read_chunk(info, chunk);
> >> + if (ret < 0)
> >> + goto out_err;
> >> + rqstp->rq_arg.pages = &info->ri_rqst->rq_pages[0];
> >> + rqstp->rq_arg.page_base = offset_in_page(offset);
> >> + rqstp->rq_arg.buflen += offset_in_page(offset);
> >> +
> >> + trace_svcrdma_post_read_chunk(&cc->cc_cid, cc->cc_sqecount);
> >> + init_completion(&cc->cc_done);
> >> + ret = svc_rdma_post_chunk_ctxt(cc);
> >> + if (ret < 0)
> >> + goto out_err;
> >> +
> >> + ret = 0;
> >> + wait_for_completion(&cc->cc_done);
> >> + if (cc->cc_status != IB_WC_SUCCESS)
> >> + ret = -EIO;
> >> +
> >> + /* Ensure svc_rdma_recv_ctxt_put() does not try to release pages */
> >> + head->rc_page_count = 0;
> >> +
> >> +out_err:
> >> + svc_rdma_read_info_free(info);
> >> + return ret;
> >> +}
> >>
>
> --
> Chuck Lever
>
>
