[PATCH v2 4/6] NFSD: Use rqstp->rq_bvec in nfsd_iter_write()

[cel@xxxxxxxxxx]

From: Chuck Lever <chuck.lever@xxxxxxxxxx>

If we can get rid of all uses of rq_vec, then it can be removed.
Replace one use of rqstp::rq_vec with rqstp::rq_bvec.

The feeling of layering violation grows stronger now that we've
included <linux/sunrpc/xdr.h> in fs/nfsd/vfs.c.

Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 fs/nfsd/vfs.c    |  5 +++--
 net/sunrpc/svc.c | 23 +++++++++++++----------
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index e92036251ee7..15195fedc44e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -31,6 +31,7 @@
 #include <linux/exportfs.h>
 #include <linux/writeback.h>
 #include <linux/security.h>
+#include <linux/sunrpc/xdr.h>
 
 #include "xdr3.h"
 
@@ -1204,8 +1205,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (stable && !fhp->fh_use_wgather)
 		flags |= RWF_SYNC;
 
-	nvecs = svc_fill_write_vector(rqstp, payload);
-	iov_iter_kvec(&iter, ITER_SOURCE, rqstp->rq_vec, nvecs, *cnt);
+	nvecs = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, payload);
+	iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt);
 	since = READ_ONCE(file->f_wb_err);
 	if (verf)
 		nfsd_copy_write_verifier(verf, nn);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 930a10cac90b..d113f44798a1 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1727,35 +1727,38 @@ EXPORT_SYMBOL_GPL(svc_encode_result_payload);
 
 /**
  * svc_fill_write_vector - Construct data argument for VFS write call
- * @rqstp: svc_rqst to operate on
+ * @rqstp: RPC execution context
  * @payload: xdr_buf containing only the write data payload
  *
- * Fills in rqstp::rq_vec, and returns the number of elements.
+ * Fills in @rqstp->rq_bvec, and returns the number of elements it
+ * populated in that array.
  */
 unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
 				   struct xdr_buf *payload)
 {
 	struct page **pages = payload->pages;
+	struct bio_vec *vec = rqstp->rq_bvec;
 	struct kvec *first = payload->head;
-	struct kvec *vec = rqstp->rq_vec;
 	size_t total = payload->len;
-	unsigned int i;
+	unsigned int base, len, i;
 
 	/* Some types of transport can present the write payload
 	 * entirely in rq_arg.pages. In this case, @first is empty.
 	 */
 	i = 0;
 	if (first->iov_len) {
-		vec[i].iov_base = first->iov_base;
-		vec[i].iov_len = min_t(size_t, total, first->iov_len);
-		total -= vec[i].iov_len;
+		len = min_t(size_t, total, first->iov_len);
+		bvec_set_virt(&vec[i], first->iov_base, len);
+		total -= len;
 		++i;
 	}
 
+	base = payload->page_base;
 	while (total) {
-		vec[i].iov_base = page_address(*pages);
-		vec[i].iov_len = min_t(size_t, total, PAGE_SIZE);
-		total -= vec[i].iov_len;
+		len = min_t(size_t, total, PAGE_SIZE);
+		bvec_set_page(&vec[i], *pages, len, base);
+		total -= len;
+		base = 0;
 		++i;
 		++pages;
 	}
-- 
2.49.0