NFSD: Replace the internals of the READ_BUF() macro

Convert the READ_BUF macro in nfs4xdr.c from open code to instead
use the new xdr_stream-style decoders already in use by the encode
side (and by the in-kernel NFS client implementation). Once this
conversion is done, each individual NFSv4 argument decoder can be
independently cleaned up to replace these macros with C code.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index c607744b3ea8..757560a3b06b 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1408,6 +1408,51 @@ int xdr_buf_subsegment(const struct xdr_buf *buf, struct xdr_buf *subbuf,
 EXPORT_SYMBOL_GPL(xdr_buf_subsegment);
 
 /**
+ * xdr_stream_subsegment - set @subbuf to a portion of @xdr
+ * @xdr: an xdr_stream set up for decoding
+ * @subbuf: the result buffer
+ * @nbytes: length of @xdr to extract, in bytes
+ *
+ * Sets up @subbuf to represent a portion of @xdr. The portion
+ * starts at the current offset in @xdr, and extends for a length
+ * of @nbytes. If this is successful, @xdr is advanced to the next
+ * position following that portion.
+ *
+ * Return values:
+ *   %true: @subbuf has been initialized, and @xdr has been advanced.
+ *   %false: a bounds error has occurred
+ */
+bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf,
+			   unsigned int nbytes)
+{
+	unsigned int remaining, offset, len;
+
+	if (xdr_buf_subsegment(xdr->buf, subbuf, xdr_stream_pos(xdr), nbytes))
+		return false;
+
+	if (subbuf->head[0].iov_len)
+		if (!__xdr_inline_decode(xdr, subbuf->head[0].iov_len))
+			return false;
+
+	remaining = subbuf->page_len;
+	offset = subbuf->page_base;
+	while (remaining) {
+		len = min_t(unsigned int, remaining, PAGE_SIZE) - offset;
+
+		if (xdr->p == xdr->end && !xdr_set_next_buffer(xdr))
+			return false;
+		if (!__xdr_inline_decode(xdr, len))
+			return false;
+
+		remaining -= len;
+		offset = 0;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_subsegment);
+
+/**
  * xdr_buf_trim - lop at most "len" bytes off the end of "buf"
  * @buf: buf to be trimmed
  * @len: number of bytes to reduce "buf" by