> 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.
> 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
