[PATCH v5 2/4] NFSD: Refactor nfsd_vfs_write()

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

Extract the common code that is to be used in the buffered and
dontcache I/O modes. This common code will also be used as the
fallback when direct I/O is requested but cannot be used.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/vfs.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 8b2dc7a88aab..ae9c41f7374e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1254,6 +1254,22 @@ static int wait_for_concurrent_writes(struct file *file)
 	return err;
 }
 
+static int
+nfsd_iocb_write(struct svc_rqst *rqstp, struct file *file, unsigned int nvecs,
+		unsigned long *cnt, struct kiocb *kiocb)
+{
+	struct iov_iter iter;
+	int host_err;
+
+	iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt);
+	host_err = vfs_iocb_iter_write(file, kiocb, &iter);
+	if (host_err < 0)
+		return host_err;
+	*cnt = host_err;
+
+	return 0;
+}
+
 /**
  * nfsd_vfs_write - write data to an already-open file
  * @rqstp: RPC execution context
@@ -1282,7 +1298,6 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	u32			stable = *stable_how;
 	struct kiocb		kiocb;
 	struct svc_export	*exp;
-	struct iov_iter		iter;
 	errseq_t		since;
 	__be32			nfserr;
 	int			host_err;
@@ -1319,25 +1334,24 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		kiocb.ki_flags |= IOCB_DSYNC;
 
 	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);
 
 	switch (nfsd_io_cache_write) {
-	case NFSD_IO_BUFFERED:
-		break;
 	case NFSD_IO_DONTCACHE:
 		if (file->f_op->fop_flags & FOP_DONTCACHE)
 			kiocb.ki_flags |= IOCB_DONTCACHE;
+		fallthrough;
+	case NFSD_IO_BUFFERED:
+		host_err = nfsd_iocb_write(rqstp, file, nvecs, cnt, &kiocb);
 		break;
 	}
-	host_err = vfs_iocb_iter_write(file, &kiocb, &iter);
 	if (host_err < 0) {
 		commit_reset_write_verifier(nn, rqstp, host_err);
 		goto out_nfserr;
 	}
-	*cnt = host_err;
 	nfsd_stats_io_write_add(nn, exp, *cnt);
 	fsnotify_modify(file);
 	host_err = filemap_check_wb_err(file->f_mapping, since);
-- 
2.51.0