Add a generic helper for FSes to validate that an atomic write is
appropriately sized (along with the other checks).

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 include/linux/fs.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6ebefb079740..9bfa9b68d800 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3648,4 +3648,16 @@ bool generic_atomic_write_valid(loff_t pos, struct iov_iter *iter)
 	return true;
 }
 
+static inline
+bool generic_atomic_write_valid_size(loff_t pos, struct iov_iter *iter,
+				unsigned int unit_min, unsigned int unit_max)
+{
+	size_t len = iov_iter_count(iter);
+
+	if (len < unit_min || len > unit_max)
+		return false;
+
+	return generic_atomic_write_valid(pos, iter);
+}
+
 #endif /* _LINUX_FS_H */
-- 
2.31.1