[net/9p] Preparation and helper functions for zero copy

This patch prepares p9_fcall structure for zero copy. Added
fields send the payload buffer information to the transport layer.
In addition it adds a 'private' field for the transport layer to
store mapped/pinned page information so that it can be freed/unpinned
during req_done.

This patch also creates trans_common.[ch] to house helper functions.
It adds the following helper functions.

p9_release_req_pages - Release pages after the transaction.
p9_nr_pages - Return number of pages needed to accomodate the payload.
payload_gup - Translates user buffer into kernel pages.

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 071fd7a8d781..7aefa6d975ac 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -689,6 +689,10 @@ struct p9_rwstat {
  * @tag: transaction id of the request
  * @offset: used by marshalling routines to track currentposition in buffer
  * @capacity: used by marshalling routines to track total capacity
+ * @pubuf: Payload user buffer given by the caller
+ * @pubuf: Payload kernel buffer given by the caller
+ * @pbuf_size: pubuf/pkbuf(only one will be !NULL) size to be read/write.
+ * @private: For transport layer's use.
  * @sdata: payload
  *
  * &p9_fcall represents the structure for all 9P RPC
@@ -705,6 +709,10 @@ struct p9_fcall {
 
         size_t offset;
         size_t capacity;
+        char __user *pubuf;
+        char *pkbuf;
+        size_t pbuf_size;
+        void *private;
 
         uint8_t *sdata;
 };