[PATCH 2/3] nfsd: use rq_bvec instead of rq_vec in nfsd_vfs_write

[Christoph Hellwig <hch@xxxxxx>]

There is no benefit in using a kvec vs a bvec for in-kernel writes,
but phasing out the kvec here will allow us to eventually remove that
array.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/nfsd/vfs.c              | 10 +++++++---
 include/linux/sunrpc/svc.h |  2 --
 net/sunrpc/svc.c           | 40 --------------------------------------
 3 files changed, 7 insertions(+), 45 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index da62082d06dc..0cc9639fba79 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1161,8 +1161,12 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 
 	trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
 
-	nvecs = svc_fill_write_vector(rqstp, payload);
-	if (WARN_ON_ONCE(nvecs > ARRAY_SIZE(rqstp->rq_vec)))
+	if (WARN_ON_ONCE(payload->tail->iov_len))
+		return -EIO;
+
+	nvecs = xdr_buf_to_bvec(rqstp->rq_bvec, ARRAY_SIZE(rqstp->rq_bvec),
+			payload);
+	if (WARN_ON_ONCE(nvecs > ARRAY_SIZE(rqstp->rq_bvec)))
 		return -EIO;
 
 	if (sb->s_export_op)
@@ -1189,7 +1193,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 	if (stable && !fhp->fh_use_wgather)
 		flags |= RWF_SYNC;
 
-	iov_iter_kvec(&iter, ITER_SOURCE, rqstp->rq_vec, nvecs, *cnt);
+	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/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 74658cca0f38..c25456738315 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -452,8 +452,6 @@ const char *	   svc_proc_name(const struct svc_rqst *rqstp);
 int		   svc_encode_result_payload(struct svc_rqst *rqstp,
 					     unsigned int offset,
 					     unsigned int length);
-unsigned int	   svc_fill_write_vector(struct svc_rqst *rqstp,
-					 struct xdr_buf *payload);
 char		  *svc_fill_symlink_pathname(struct svc_rqst *rqstp,
 					     struct kvec *first, void *p,
 					     size_t total);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index e7f9c295d13c..9fd370d6676c 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1713,46 +1713,6 @@ int svc_encode_result_payload(struct svc_rqst *rqstp, unsigned int offset,
 }
 EXPORT_SYMBOL_GPL(svc_encode_result_payload);
 
-/**
- * svc_fill_write_vector - Construct data argument for VFS write call
- * @rqstp: svc_rqst to operate on
- * @payload: xdr_buf containing only the write data payload
- *
- * Fills in rqstp::rq_vec, and returns the number of elements.
- */
-unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
-				   struct xdr_buf *payload)
-{
-	struct page **pages = payload->pages;
-	struct kvec *first = payload->head;
-	struct kvec *vec = rqstp->rq_vec;
-	size_t total = payload->len;
-	unsigned int 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;
-		++i;
-	}
-
-	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;
-		++i;
-		++pages;
-	}
-
-	WARN_ON_ONCE(i > ARRAY_SIZE(rqstp->rq_vec));
-	return i;
-}
-EXPORT_SYMBOL_GPL(svc_fill_write_vector);
-
 /**
  * svc_fill_symlink_pathname - Construct pathname argument for VFS symlink call
  * @rqstp: svc_rqst to operate on
-- 
2.47.2