new primitive: iov_iter_alignment()

returns the value aligned as badly as the worst remaining segment
in iov_iter is.  Use instead of open-coded equivalents.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 25 insertions, 0 deletions

diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 22ec1ef068a8..2f762cc21080 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -195,3 +195,28 @@ size_t iov_iter_single_seg_count(const struct iov_iter *i)
 		return min(i->count, iov->iov_len - i->iov_offset);
 }
 EXPORT_SYMBOL(iov_iter_single_seg_count);
+
+unsigned long iov_iter_alignment(const struct iov_iter *i)
+{
+	const struct iovec *iov = i->iov;
+	unsigned long res;
+	size_t size = i->count;
+	size_t n;
+
+	if (!size)
+		return 0;
+
+	res = (unsigned long)iov->iov_base + i->iov_offset;
+	n = iov->iov_len - i->iov_offset;
+	if (n >= size)
+		return res | size;
+	size -= n;
+	res |= n;
+	while (size > (++iov)->iov_len) {
+		res |= (unsigned long)iov->iov_base | iov->iov_len;
+		size -= iov->iov_len;
+	}
+	res |= (unsigned long)iov->iov_base | size;
+	return res;
+}
+EXPORT_SYMBOL(iov_iter_alignment);