1 files changed, 27 insertions, 0 deletions
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 45204cd5ccd8..0b677f8f9bad 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -262,3 +262,30 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 	return (res == n ? len : res * PAGE_SIZE) - *start;
 }
 EXPORT_SYMBOL(iov_iter_get_pages);
+
+int iov_iter_npages(const struct iov_iter *i, int maxpages)
+{
+	size_t offset = i->iov_offset;
+	size_t size = i->count;
+	const struct iovec *iov = i->iov;
+	int npages = 0;
+	int n;
+
+	for (n = 0; size && n < i->nr_segs; n++, iov++) {
+		unsigned long addr = (unsigned long)iov->iov_base + offset;
+		size_t len = iov->iov_len - offset;
+		offset = 0;
+		if (unlikely(!len))	/* empty segment */
+			continue;
+		if (len > size)
+			len = size;
+		npages += (addr + len + PAGE_SIZE - 1) / PAGE_SIZE
+			  - addr / PAGE_SIZE;
+		if (npages >= maxpages)	/* don't bother going further */
+			return maxpages;
+		size -= len;
+		offset = 0;
+	}
+	return min(npages, maxpages);
+}
+EXPORT_SYMBOL(iov_iter_npages);