1 files changed, 41 insertions, 13 deletions

diff --git a/kernel/lib/scatterlist.c b/kernel/lib/scatterlist.c
index f6d1f8899..ebe3b7edd 100644
--- a/kernel/lib/scatterlist.c
+++ b/kernel/lib/scatterlist.c
@@ -56,6 +56,38 @@ int sg_nents(struct scatterlist *sg)
 }
 EXPORT_SYMBOL(sg_nents);
 
+/**
+ * sg_nents_for_len - return total count of entries in scatterlist
+ *                    needed to satisfy the supplied length
+ * @sg:		The scatterlist
+ * @len:	The total required length
+ *
+ * Description:
+ * Determines the number of entries in sg that are required to meet
+ * the supplied length, taking into acount chaining as well
+ *
+ * Returns:
+ *   the number of sg entries needed, negative error on failure
+ *
+ **/
+int sg_nents_for_len(struct scatterlist *sg, u64 len)
+{
+	int nents;
+	u64 total;
+
+	if (!len)
+		return 0;
+
+	for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
+		nents++;
+		total += sg->length;
+		if (total >= len)
+			return nents;
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL(sg_nents_for_len);
 
 /**
  * sg_last - return the last scatterlist entry in a list
@@ -73,16 +105,12 @@ EXPORT_SYMBOL(sg_nents);
  **/
 struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
 {
-#ifndef CONFIG_ARCH_HAS_SG_CHAIN
-	struct scatterlist *ret = &sgl[nents - 1];
-#else
 	struct scatterlist *sg, *ret = NULL;
 	unsigned int i;
 
 	for_each_sg(sgl, sg, nents, i)
 		ret = sg;
 
-#endif
 #ifdef CONFIG_DEBUG_SG
 	BUG_ON(sgl[0].sg_magic != SG_MAGIC);
 	BUG_ON(!sg_is_last(ret));
@@ -618,9 +646,8 @@ EXPORT_SYMBOL(sg_miter_stop);
  * Returns the number of copied bytes.
  *
  **/
-static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
-			     void *buf, size_t buflen, off_t skip,
-			     bool to_buffer)
+size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
+		      size_t buflen, off_t skip, bool to_buffer)
 {
 	unsigned int offset = 0;
 	struct sg_mapping_iter miter;
@@ -657,6 +684,7 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
 	local_irq_restore_nort(flags);
 	return offset;
 }
+EXPORT_SYMBOL(sg_copy_buffer);
 
 /**
  * sg_copy_from_buffer - Copy from a linear buffer to an SG list
@@ -669,9 +697,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
  *
  **/
 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
-			   void *buf, size_t buflen)
+			   const void *buf, size_t buflen)
 {
-	return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
+	return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
 }
 EXPORT_SYMBOL(sg_copy_from_buffer);
 
@@ -697,16 +725,16 @@ EXPORT_SYMBOL(sg_copy_to_buffer);
  * @sgl:		 The SG list
  * @nents:		 Number of SG entries
  * @buf:		 Where to copy from
- * @skip:		 Number of bytes to skip before copying
  * @buflen:		 The number of bytes to copy
+ * @skip:		 Number of bytes to skip before copying
  *
  * Returns the number of copied bytes.
  *
  **/
 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
-			    void *buf, size_t buflen, off_t skip)
+			    const void *buf, size_t buflen, off_t skip)
 {
-	return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
+	return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false);
 }
 EXPORT_SYMBOL(sg_pcopy_from_buffer);
 
@@ -715,8 +743,8 @@ EXPORT_SYMBOL(sg_pcopy_from_buffer);
  * @sgl:		 The SG list
  * @nents:		 Number of SG entries
  * @buf:		 Where to copy to
- * @skip:		 Number of bytes to skip before copying
  * @buflen:		 The number of bytes to copy
+ * @skip:		 Number of bytes to skip before copying
  *
  * Returns the number of copied bytes.
  *