NFSD: Use rqstp->rq_bvec in nfsd_iter_write()

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
<linux/sunrpc/xdr.h> is included in fs/nfsd/vfs.c.

Suggested-by: Christoph Hellwig <[email protected]>
Signed-off-by: Chuck Lever <[email protected]>

Author: chucklever

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"
 
@@ -1206,8 +1207,8 @@ 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);