When a buffered write submitted with IOCB_DONTCACHE has been successfully
submitted, call filemap_fdatawrite_range_kick() to kick off the IO.
File systems call generic_write_sync() for any successful buffered write
submission, hence add the logic here rather than needing to modify the
file system.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/fs.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 653b5efa3d3f..58a618853574 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2912,6 +2912,11 @@ static inline ssize_t generic_write_sync(struct kiocb *iocb, ssize_t count)
 				(iocb->ki_flags & IOCB_SYNC) ? 0 : 1);
 		if (ret)
 			return ret;
+	} else if (iocb->ki_flags & IOCB_DONTCACHE) {
+		struct address_space *mapping = iocb->ki_filp->f_mapping;
+
+		filemap_fdatawrite_range_kick(mapping, iocb->ki_pos,
+					      iocb->ki_pos + count);
 	}
 
 	return count;
-- 
2.45.2