[PATCH v5 5/5] NFSD: Encode a full READ_PLUS reply

[schumaker.anna@gmail.com]

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

Reply to the client with multiple hole and data segments. I use the
result of the first vfs_llseek() call for encoding as an optimization so
we don't have to immediately repeat the call.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

---
v5: Truncate the encode to the last segment length if we're returning a
    short read
---
 fs/nfsd/nfs4xdr.c | 40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 856606263c1d..eec23a7d5ca0 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4603,16 +4603,18 @@ nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
 static __be32
 nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
 			    struct nfsd4_read *read,
-			    unsigned long *maxcount, u32 *eof)
+			    unsigned long *maxcount, u32 *eof,
+			    loff_t *pos)
 {
 	struct xdr_stream *xdr = &resp->xdr;
 	struct file *file = read->rd_nf->nf_file;
 	int starting_len = xdr->buf->len;
-	loff_t hole_pos = vfs_llseek(file, read->rd_offset, SEEK_HOLE);
+	loff_t hole_pos;
 	__be32 nfserr;
 	__be32 *p, tmp;
 	__be64 tmp64;
 
+	hole_pos = pos ? *pos : vfs_llseek(file, read->rd_offset, SEEK_HOLE);
 	if (hole_pos > read->rd_offset)
 		*maxcount = min_t(unsigned long, *maxcount, hole_pos - read->rd_offset);
 
@@ -4677,8 +4679,10 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
 	struct xdr_stream *xdr = &resp->xdr;
 	struct file *file;
 	int starting_len = xdr->buf->len;
+	int last_segment = xdr->buf->len;
 	int segments = 0;
 	__be32 *p, tmp;
+	bool is_data;
 	loff_t pos;
 	u32 eof;
 
@@ -4702,29 +4706,22 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
 	if (eof)
 		goto out;
 
-	pos = vfs_llseek(file, read->rd_offset, SEEK_DATA);
-	if (pos == -ENXIO)
-		pos = i_size_read(file_inode(file));
-	else if (pos < 0)
-		pos = read->rd_offset;
+	pos = vfs_llseek(file, read->rd_offset, SEEK_HOLE);
+	is_data = pos > read->rd_offset;
 
-	if (pos == read->rd_offset) {
+	while (count > 0 && !eof) {
 		maxcount = count;
-		nfserr = nfsd4_encode_read_plus_data(resp, read, &maxcount, &eof);
-		if (nfserr)
-			goto out;
-		count -= maxcount;
-		read->rd_offset += maxcount;
-		segments++;
-	}
-
-	if (count > 0 && !eof) {
-		maxcount = count;
-		nfserr = nfsd4_encode_read_plus_hole(resp, read, &maxcount, &eof);
+		if (is_data)
+			nfserr = nfsd4_encode_read_plus_data(resp, read, &maxcount, &eof,
+						segments == 0 ? &pos : NULL);
+		else
+			nfserr = nfsd4_encode_read_plus_hole(resp, read, &maxcount, &eof);
 		if (nfserr)
 			goto out;
 		count -= maxcount;
 		read->rd_offset += maxcount;
+		is_data = !is_data;
+		last_segment = xdr->buf->len;
 		segments++;
 	}
 
@@ -4736,7 +4733,10 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
 		write_bytes_to_xdr_buf(xdr->buf, starting_len,     &tmp, 4);
 		tmp = htonl(segments);
 		write_bytes_to_xdr_buf(xdr->buf, starting_len + 4, &tmp, 4);
-		nfserr = nfs_ok;
+		if (nfserr) {
+			xdr_truncate_encode(xdr, last_segment);
+			nfserr = nfs_ok;
+		}
 	}
 
 	return nfserr;
-- 
2.28.0