From: Chuck Lever <chuck.lever@oracle.com>
Date: Wed, 15 Apr 2020 17:36:22 -0400
Subject: [PATCH] SUNRPC: Revert 241b1f419f0e ("SUNRPC: Remove xdr_buf_trim()")
Patch-mainline: Never, kabi workaround
References: git-fixes

This patch (mainline commit 0a8e7b7d0846) was temporarily in SLE15-SP2, but
was reverted because it introduced a regression.  However as it added an
EXPORT_SYMBOL, the revertion broke the kabi.

So this stub-patch just restores that symbol - which is unused.

Acked-by: NeilBrown <neilb@suse.com>

---
 include/linux/sunrpc/xdr.h          |    1 
 net/sunrpc/xdr.c                    |   41 ++++++++++++++++++++++++++++++++++++

--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -187,6 +187,7 @@ extern void xdr_shift_buf(struct xdr_buf
 extern void xdr_buf_from_iov(struct kvec *, struct xdr_buf *);
 extern int xdr_buf_subsegment(struct xdr_buf *, struct xdr_buf *, unsigned int, unsigned int);
 extern int xdr_buf_read_mic(struct xdr_buf *, struct xdr_netobj *, unsigned int);
+extern void xdr_buf_trim(struct xdr_buf *, unsigned int);
 extern int read_bytes_from_xdr_buf(struct xdr_buf *, unsigned int, void *, unsigned int);
 extern int write_bytes_to_xdr_buf(struct xdr_buf *, unsigned int, void *, unsigned int);
 
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1154,6 +1154,47 @@ xdr_buf_subsegment(struct xdr_buf *buf,
 }
 EXPORT_SYMBOL_GPL(xdr_buf_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
+ *
+ * Trim an xdr_buf by the given number of bytes by fixing up the lengths. Note
+ * that it's possible that we'll trim less than that amount if the xdr_buf is
+ * too small, or if (for instance) it's all in the head and the parser has
+ * already read too far into it.
+ */
+void xdr_buf_trim(struct xdr_buf *buf, unsigned int len)
+{
+	size_t cur;
+	unsigned int trim = len;
+
+	if (buf->tail[0].iov_len) {
+		cur = min_t(size_t, buf->tail[0].iov_len, trim);
+		buf->tail[0].iov_len -= cur;
+		trim -= cur;
+		if (!trim)
+			goto fix_len;
+	}
+
+	if (buf->page_len) {
+		cur = min_t(unsigned int, buf->page_len, trim);
+		buf->page_len -= cur;
+		trim -= cur;
+		if (!trim)
+			goto fix_len;
+	}
+
+	if (buf->head[0].iov_len) {
+		cur = min_t(size_t, buf->head[0].iov_len, trim);
+		buf->head[0].iov_len -= cur;
+		trim -= cur;
+	}
+fix_len:
+	buf->len -= (len - trim);
+}
+EXPORT_SYMBOL_GPL(xdr_buf_trim);
+
 static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned int len)
 {
 	unsigned int this_len;