[RFC 5/9] iov_iter: Add iov_iter_fault_in_writeable()

[Andreas Gruenbacher]

Add the equivalent of iov_iter_fault_in_readable(), but for pages that
will be written to.

While at it, fix an indentation error in iov_iter_fault_in_readable().

Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
 include/linux/uio.h |  1 +
 lib/iov_iter.c      | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index d3ec87706d75..6811eb6ac6e3 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -124,6 +124,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
 void iov_iter_revert(struct iov_iter *i, size_t bytes);
 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
+int iov_iter_fault_in_writeable(struct iov_iter *i, size_t bytes);
 size_t iov_iter_single_seg_count(const struct iov_iter *i);
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 			 struct iov_iter *i);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index c701b7a187f2..317c94eac907 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -480,13 +480,31 @@ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 		iterate_iovec(i, bytes, v, iov, skip, ({
 			err = fault_in_pages_readable(v.iov_base, v.iov_len);
 			if (unlikely(err))
-			return err;
+				return err;
 		0;}))
 	}
 	return 0;
 }
 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 
+int iov_iter_fault_in_writeable(struct iov_iter *i, size_t bytes)
+{
+	size_t skip = i->iov_offset;
+	const struct iovec *iov;
+	int err;
+	struct iovec v;
+
+	if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
+		iterate_iovec(i, bytes, v, iov, skip, ({
+			err = fault_in_pages_writeable(v.iov_base, v.iov_len);
+			if (unlikely(err))
+				return err;
+		0;}))
+	}
+	return 0;
+}
+EXPORT_SYMBOL(iov_iter_fault_in_writeable);
+
 void iov_iter_init(struct iov_iter *i, unsigned int direction,
 			const struct iovec *iov, unsigned long nr_segs,
 			size_t count)
-- 
2.26.3