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Commit 193bcb7b authored by Chuck Lever's avatar Chuck Lever Committed by J. Bruce Fields
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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 a97c331f ("svcrdma: Handle additional inline content"),
is no longer needed and can be removed.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent eae03e2a

net/sunrpc/xprtrdma/svc_rdma_rw.c

+15 −93
Original line number Diff line number Diff line
@@ -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.

	/* 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.

	 */

		info->ri_pageoff += padlen;

		if (info->ri_pageoff == PAGE_SIZE) {

			info->ri_pageno++;

			info->ri_pageoff = 0;

		}

	}

	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;

}