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 <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index 1f34fae7aec0299042555cee77b6e16d6bbfe081..7dcda4597057373c3ae17b426e487c47c6c2c2c0 100644 (file)
--- 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);
-
-               info->ri_chunklen += padlen;
+       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;
 
-               /* 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;
 }