From: Chuck Lever <chuck.lever@oracle.com>
Date: Mon, 7 May 2018 15:27:32 -0400
Subject: svcrdma: Simplify svc_rdma_recv_ctxt_put
Patch-mainline: v4.18-rc1
Git-commit: 1e5f4160745690a0476929d128a336cae95c1df9
References: bsc#1103992 FATE#326009

Currently svc_rdma_recv_ctxt_put's callers have to know whether they
want to free the ctxt's pages or not. This means the human
developers have to know when and why to set that free_pages
argument.

Instead, the ctxt should carry that information with it so that
svc_rdma_recv_ctxt_put does the right thing no matter who is
calling.

We want to keep track of the number of pages in the Receive buffer
separately from the number of pages pulled over by RDMA Read. This
is so that the correct number of pages can be freed properly and
that number is well-documented.

So now, rc_hdr_count is the number of pages consumed by head[0]
(ie., the page index where the Read chunk should start); and
rc_page_count is always the number of pages that need to be released
when the ctxt is put.

The @free_pages argument is no longer needed.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/sunrpc/svc_rdma.h         |    3 --
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |   41 +++++++++++++++++---------------
 net/sunrpc/xprtrdma/svc_rdma_rw.c       |    4 +--
 3 files changed, 25 insertions(+), 23 deletions(-)

--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -173,8 +173,7 @@ extern int svc_rdma_handle_bc_reply(stru
 extern void svc_rdma_recv_ctxts_destroy(struct svcxprt_rdma *rdma);
 extern bool svc_rdma_post_recvs(struct svcxprt_rdma *rdma);
 extern void svc_rdma_recv_ctxt_put(struct svcxprt_rdma *rdma,
-				   struct svc_rdma_recv_ctxt *ctxt,
-				   int free_pages);
+				   struct svc_rdma_recv_ctxt *ctxt);
 extern void svc_rdma_flush_recv_queues(struct svcxprt_rdma *rdma);
 extern int svc_rdma_recvfrom(struct svc_rqst *);
 
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -175,18 +175,15 @@ static void svc_rdma_recv_ctxt_unmap(str
  * svc_rdma_recv_ctxt_put - Return recv_ctxt to free list
  * @rdma: controlling svcxprt_rdma
  * @ctxt: object to return to the free list
- * @free_pages: Non-zero if rc_pages should be freed
  *
  */
 void svc_rdma_recv_ctxt_put(struct svcxprt_rdma *rdma,
-			    struct svc_rdma_recv_ctxt *ctxt,
-			    int free_pages)
+			    struct svc_rdma_recv_ctxt *ctxt)
 {
 	unsigned int i;
 
-	if (free_pages)
-		for (i = 0; i < ctxt->rc_page_count; i++)
-			put_page(ctxt->rc_pages[i]);
+	for (i = 0; i < ctxt->rc_page_count; i++)
+		put_page(ctxt->rc_pages[i]);
 	spin_lock(&rdma->sc_recv_lock);
 	list_add(&ctxt->rc_list, &rdma->sc_recv_ctxts);
 	spin_unlock(&rdma->sc_recv_lock);
@@ -243,11 +240,11 @@ static int svc_rdma_post_recv(struct svc
 
 err_put_ctxt:
 	svc_rdma_recv_ctxt_unmap(rdma, ctxt);
-	svc_rdma_recv_ctxt_put(rdma, ctxt, 1);
+	svc_rdma_recv_ctxt_put(rdma, ctxt);
 	return -ENOMEM;
 err_post:
 	svc_rdma_recv_ctxt_unmap(rdma, ctxt);
-	svc_rdma_recv_ctxt_put(rdma, ctxt, 1);
+	svc_rdma_recv_ctxt_put(rdma, ctxt);
 	svc_xprt_put(&rdma->sc_xprt);
 	return ret;
 }
@@ -316,7 +313,7 @@ flushed:
 		       ib_wc_status_msg(wc->status),
 		       wc->status, wc->vendor_err);
 post_err:
-	svc_rdma_recv_ctxt_put(rdma, ctxt, 1);
+	svc_rdma_recv_ctxt_put(rdma, ctxt);
 	set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
 	svc_xprt_enqueue(&rdma->sc_xprt);
 out:
@@ -334,11 +331,11 @@ void svc_rdma_flush_recv_queues(struct s
 
 	while ((ctxt = svc_rdma_next_recv_ctxt(&rdma->sc_read_complete_q))) {
 		list_del(&ctxt->rc_list);
-		svc_rdma_recv_ctxt_put(rdma, ctxt, 1);
+		svc_rdma_recv_ctxt_put(rdma, ctxt);
 	}
 	while ((ctxt = svc_rdma_next_recv_ctxt(&rdma->sc_rq_dto_q))) {
 		list_del(&ctxt->rc_list);
-		svc_rdma_recv_ctxt_put(rdma, ctxt, 1);
+		svc_rdma_recv_ctxt_put(rdma, ctxt);
 	}
 }
 
@@ -383,16 +380,19 @@ static void svc_rdma_build_arg_xdr(struc
 		len -= min_t(u32, len, ctxt->rc_sges[sge_no].length);
 		sge_no++;
 	}
+	ctxt->rc_hdr_count = sge_no;
 	rqstp->rq_respages = &rqstp->rq_pages[sge_no];
 	rqstp->rq_next_page = rqstp->rq_respages + 1;
 
 	/* If not all pages were used from the SGL, free the remaining ones */
-	len = sge_no;
 	while (sge_no < ctxt->rc_recv_wr.num_sge) {
 		page = ctxt->rc_pages[sge_no++];
 		put_page(page);
 	}
-	ctxt->rc_page_count = len;
+
+	/* @ctxt's pages have all been released or moved to @rqstp->rq_pages.
+	 */
+	ctxt->rc_page_count = 0;
 
 	/* Set up tail */
 	rqstp->rq_arg.tail[0].iov_base = NULL;
@@ -602,11 +602,14 @@ static void rdma_read_complete(struct sv
 {
 	int page_no;
 
-	/* Copy RPC pages */
+	/* Move Read chunk pages to rqstp so that they will be released
+	 * when svc_process is done with them.
+	 */
 	for (page_no = 0; page_no < head->rc_page_count; page_no++) {
 		put_page(rqstp->rq_pages[page_no]);
 		rqstp->rq_pages[page_no] = head->rc_pages[page_no];
 	}
+	head->rc_page_count = 0;
 
 	/* Point rq_arg.pages past header */
 	rqstp->rq_arg.pages = &rqstp->rq_pages[head->rc_hdr_count];
@@ -777,7 +780,7 @@ int svc_rdma_recvfrom(struct svc_rqst *r
 	if (svc_rdma_is_backchannel_reply(xprt, p)) {
 		ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt, p,
 					       &rqstp->rq_arg);
-		svc_rdma_recv_ctxt_put(rdma_xprt, ctxt, 0);
+		svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
 		return ret;
 	}
 
@@ -786,7 +789,7 @@ int svc_rdma_recvfrom(struct svc_rqst *r
 		goto out_readchunk;
 
 complete:
-	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt, 0);
+	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
 	rqstp->rq_prot = IPPROTO_MAX;
 	svc_xprt_copy_addrs(rqstp, xprt);
 	return rqstp->rq_arg.len;
@@ -799,16 +802,16 @@ out_readchunk:
 
 out_err:
 	svc_rdma_send_error(rdma_xprt, p, ret);
-	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt, 0);
+	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
 	return 0;
 
 out_postfail:
 	if (ret == -EINVAL)
 		svc_rdma_send_error(rdma_xprt, p, ret);
-	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt, 1);
+	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
 	return ret;
 
 out_drop:
-	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt, 1);
+	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
 	return 0;
 }
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -281,7 +281,7 @@ static void svc_rdma_wc_read_done(struct
 			pr_err("svcrdma: read ctx: %s (%u/0x%x)\n",
 			       ib_wc_status_msg(wc->status),
 			       wc->status, wc->vendor_err);
-		svc_rdma_recv_ctxt_put(rdma, info->ri_readctxt, 1);
+		svc_rdma_recv_ctxt_put(rdma, info->ri_readctxt);
 	} else {
 		spin_lock(&rdma->sc_rq_dto_lock);
 		list_add_tail(&info->ri_readctxt->rc_list,
@@ -833,7 +833,7 @@ int svc_rdma_recv_read_chunk(struct svcx
 	 * head->rc_arg. Pages involved with RDMA Read I/O are
 	 * transferred there.
 	 */
-	head->rc_hdr_count = head->rc_page_count;
+	head->rc_page_count = head->rc_hdr_count;
 	head->rc_arg.head[0] = rqstp->rq_arg.head[0];
 	head->rc_arg.tail[0] = rqstp->rq_arg.tail[0];
 	head->rc_arg.pages = head->rc_pages;