iov_iter: Separate type from direction and use accessor functions

In the iov_iter struct, separate the iterator type from the iterator
direction and use accessor functions to access them in most places.

Convert a bunch of places to use switch-statements to access them rather
then chains of bitwise-AND statements.  This makes it easier to add further
iterator types.  Also, this can be more efficient as to implement a switch
of small contiguous integers, the compiler can use ~50% fewer compare
instructions than it has to use bitwise-and instructions.

Further, cease passing the iterator type into the iterator setup function.
The iterator function can set that itself.  Only the direction is required.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/page_io.c b/mm/page_io.c
index aafd19ec1db4..86de453a60cf 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -294,7 +294,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
 		};
 		struct iov_iter from;
 
-		iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE);
+		iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
 		init_sync_kiocb(&kiocb, swap_file);
 		kiocb.ki_pos = page_file_offset(page);