From 193bcb7b3719a315814dce40fc8dcd1af786ea64 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Fri, 18 Aug 2017 11:12:35 -0400 Subject: [PATCH] svcrdma: Populate tail iovec when receiving So that NFS WRITE payloads can eventually be placed directly into a file's page cache, enable the RPC-over-RDMA transport to present these payloads in the xdr_buf's page list, while placing trailing content (such as a GETATTR operation) in the xdr_buf's tail. After this change, the RPC-over-RDMA's "copy tail" hack, added by commit a97c331f9aa9 ("svcrdma: Handle additional inline content"), is no longer needed and can be removed. Signed-off-by: Chuck Lever Signed-off-by: J. Bruce Fields --- net/sunrpc/xprtrdma/svc_rdma_rw.c | 108 +++++------------------------- 1 file changed, 15 insertions(+), 93 deletions(-) diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c index 1f34fae7aec0..7dcda4597057 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c @@ -691,78 +691,6 @@ static int svc_rdma_build_read_chunk(struct svc_rqst *rqstp, return ret; } -/* If there is inline content following the Read chunk, append it to - * the page list immediately following the data payload. This has to - * be done after the reader function has determined how many pages - * were consumed for RDMA Read. - * - * On entry, ri_pageno and ri_pageoff point directly to the end of the - * page list. On exit, both have been updated to the new "next byte". - * - * Assumptions: - * - Inline content fits entirely in rq_pages[0] - * - Trailing content is only a handful of bytes - */ -static int svc_rdma_copy_tail(struct svc_rqst *rqstp, - struct svc_rdma_read_info *info) -{ - struct svc_rdma_op_ctxt *head = info->ri_readctxt; - unsigned int tail_length, remaining; - u8 *srcp, *destp; - - /* Assert that all inline content fits in page 0. This is an - * implementation limit, not a protocol limit. - */ - if (head->arg.head[0].iov_len > PAGE_SIZE) { - pr_warn_once("svcrdma: too much trailing inline content\n"); - return -EINVAL; - } - - srcp = head->arg.head[0].iov_base; - srcp += info->ri_position; - tail_length = head->arg.head[0].iov_len - info->ri_position; - remaining = tail_length; - - /* If there is room on the last page in the page list, try to - * fit the trailing content there. - */ - if (info->ri_pageoff > 0) { - unsigned int len; - - len = min_t(unsigned int, remaining, - PAGE_SIZE - info->ri_pageoff); - destp = page_address(rqstp->rq_pages[info->ri_pageno]); - destp += info->ri_pageoff; - - memcpy(destp, srcp, len); - srcp += len; - destp += len; - info->ri_pageoff += len; - remaining -= len; - - if (info->ri_pageoff == PAGE_SIZE) { - info->ri_pageno++; - info->ri_pageoff = 0; - } - } - - /* Otherwise, a fresh page is needed. */ - if (remaining) { - head->arg.pages[info->ri_pageno] = - rqstp->rq_pages[info->ri_pageno]; - head->count++; - - destp = page_address(rqstp->rq_pages[info->ri_pageno]); - memcpy(destp, srcp, remaining); - info->ri_pageoff += remaining; - } - - head->arg.page_len += tail_length; - head->arg.len += tail_length; - head->arg.buflen += tail_length; - return 0; -} - /* Construct RDMA Reads to pull over a normal Read chunk. The chunk * data lands in the page list of head->arg.pages. * @@ -787,34 +715,28 @@ static int svc_rdma_build_normal_read_chunk(struct svc_rqst *rqstp, if (ret < 0) goto out; - /* Read chunk may need XDR round-up (see RFC 5666, s. 3.7). + /* Split the Receive buffer between the head and tail + * buffers at Read chunk's position. XDR roundup of the + * chunk is not included in either the pagelist or in + * the tail. */ - if (info->ri_chunklen & 3) { - u32 padlen = 4 - (info->ri_chunklen & 3); + head->arg.tail[0].iov_base = + head->arg.head[0].iov_base + info->ri_position; + head->arg.tail[0].iov_len = + head->arg.head[0].iov_len - info->ri_position; + head->arg.head[0].iov_len = info->ri_position; - info->ri_chunklen += padlen; - - /* NB: data payload always starts on XDR alignment, - * thus the pad can never contain a page boundary. - */ - info->ri_pageoff += padlen; - if (info->ri_pageoff == PAGE_SIZE) { - info->ri_pageno++; - info->ri_pageoff = 0; - } - } + /* Read chunk may need XDR roundup (see RFC 5666, s. 3.7). + * + * NFSv2/3 write decoders need the length of the tail to + * contain the size of the roundup padding. + */ + head->arg.tail[0].iov_len += 4 - (info->ri_chunklen & 3); head->arg.page_len = info->ri_chunklen; head->arg.len += info->ri_chunklen; head->arg.buflen += info->ri_chunklen; - if (info->ri_position < head->arg.head[0].iov_len) { - ret = svc_rdma_copy_tail(rqstp, info); - if (ret < 0) - goto out; - } - head->arg.head[0].iov_len = info->ri_position; - out: return ret; }