[RFC,iov_iter v2 2/8] iov_iter: Introduce iter_copy_type

[Joe Damato <jdamato@fastly.com>]

struct iov_iter has a new member: iter_copy_type. This field holds a value
designating which type of copy to use: a regular temporal copy (ITER_COPY)
or a non-temporal copy (ITER_NOCACHE_COPY).

iov_iter initializers have been updated to set the default ITER_COPY
type.

Signed-off-by: Joe Damato <jdamato@fastly.com>
---
 include/linux/uio.h | 17 +++++++++++++++++
 lib/iov_iter.c      |  6 ++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 739285f..59573ee 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -28,6 +28,12 @@ enum iter_type {
 	ITER_DISCARD,
 };
 
+enum iter_copy_type {
+	/* iter copy types */
+	ITER_COPY,
+	ITER_NOCACHE_COPY,
+};
+
 struct iov_iter_state {
 	size_t iov_offset;
 	size_t count;
@@ -35,6 +41,7 @@ struct iov_iter_state {
 };
 
 struct iov_iter {
+	u8 iter_copy_type;
 	u8 iter_type;
 	bool nofault;
 	bool data_source;
@@ -62,6 +69,11 @@ static inline enum iter_type iov_iter_type(const struct iov_iter *i)
 	return i->iter_type;
 }
 
+static inline enum iter_copy_type iov_iter_copy_type(const struct iov_iter *i)
+{
+	return i->iter_copy_type;
+}
+
 static inline void iov_iter_save_state(struct iov_iter *iter,
 				       struct iov_iter_state *state)
 {
@@ -95,6 +107,11 @@ static inline bool iov_iter_is_discard(const struct iov_iter *i)
 	return iov_iter_type(i) == ITER_DISCARD;
 }
 
+static inline bool iov_iter_copy_is_nt(const struct iov_iter *i)
+{
+	return iov_iter_copy_type(i) == ITER_NOCACHE_COPY;
+}
+
 static inline bool iov_iter_is_xarray(const struct iov_iter *i)
 {
 	return iov_iter_type(i) == ITER_XARRAY;
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 6dd5330..d32d7e5 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -511,6 +511,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
 {
 	WARN_ON(direction & ~(READ | WRITE));
 	*i = (struct iov_iter) {
+		.iter_copy_type = ITER_COPY,
 		.iter_type = ITER_IOVEC,
 		.nofault = false,
 		.data_source = direction,
@@ -1175,6 +1176,7 @@ void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
 {
 	WARN_ON(direction & ~(READ | WRITE));
 	*i = (struct iov_iter){
+		.iter_copy_type = ITER_COPY,
 		.iter_type = ITER_KVEC,
 		.data_source = direction,
 		.kvec = kvec,
@@ -1191,6 +1193,7 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
 {
 	WARN_ON(direction & ~(READ | WRITE));
 	*i = (struct iov_iter){
+		.iter_copy_type = ITER_COPY,
 		.iter_type = ITER_BVEC,
 		.data_source = direction,
 		.bvec = bvec,
@@ -1208,6 +1211,7 @@ void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
 	BUG_ON(direction != READ);
 	WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
 	*i = (struct iov_iter){
+		.iter_copy_type = ITER_COPY,
 		.iter_type = ITER_PIPE,
 		.data_source = false,
 		.pipe = pipe,
@@ -1237,6 +1241,7 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
 {
 	BUG_ON(direction & ~1);
 	*i = (struct iov_iter) {
+		.iter_copy_type = ITER_COPY,
 		.iter_type = ITER_XARRAY,
 		.data_source = direction,
 		.xarray = xarray,
@@ -1260,6 +1265,7 @@ void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
 {
 	BUG_ON(direction != READ);
 	*i = (struct iov_iter){
+		.iter_copy_type = ITER_COPY,
 		.iter_type = ITER_DISCARD,
 		.data_source = false,
 		.count = count,
-- 
2.7.4