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, 5 insertions, 5 deletions

diff --git a/include/linux/uio.h b/include/linux/uio.h
index fcabc959c794..3d8f1acc142c 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -29,7 +29,7 @@ enum iter_type {
 };
 
 struct iov_iter {
-	int type;
+	unsigned int type;
 	size_t iov_offset;
 	size_t count;
 	union {
@@ -212,13 +212,13 @@ size_t copy_to_iter_mcsafe(void *addr, size_t bytes, struct iov_iter *i)
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
 unsigned long iov_iter_alignment(const struct iov_iter *i);
 unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
-void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
+void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,
 			unsigned long nr_segs, size_t count);
-void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
+void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec *kvec,
 			unsigned long nr_segs, size_t count);
-void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
+void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
 			unsigned long nr_segs, size_t count);
-void iov_iter_pipe(struct iov_iter *i, int direction, struct pipe_inode_info *pipe,
+void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode_info *pipe,
 			size_t count);
 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 			size_t maxsize, unsigned maxpages, size_t *start);