[PATCH v2 1/2] net/9p: distinguish zero-copy requests

[Christian Schoenebeck <linux_oss@crudebyte.com>]

Add boolean `zc` member to struct p9_fcall to distinguish zero-copy
messages (not using the linear `sdata` buffer for message payload) from
regular messages (which do copy message payload to `sdata` before being
further processed).

This new member is appended to end of structure to avoid inserting huge
padding in generated layout.

Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
---
 include/net/9p/9p.h | 2 ++
 net/9p/client.c     | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 13abe013af21..429adf6be29c 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -531,6 +531,7 @@ struct p9_rstatfs {
  * @offset: used by marshalling routines to track current position in buffer
  * @capacity: used by marshalling routines to track total malloc'd capacity
  * @sdata: payload
+ * @zc: whether zero-copy is used
  *
  * &p9_fcall represents the structure for all 9P RPC
  * transactions.  Requests are packaged into fcalls, and reponses
@@ -549,6 +550,7 @@ struct p9_fcall {
 
 	struct kmem_cache *cache;
 	u8 *sdata;
+	bool zc;
 };
 
 int p9_errstr2errno(char *errstr, int len);
diff --git a/net/9p/client.c b/net/9p/client.c
index aaa37b07e30a..c7935e392812 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -680,6 +680,9 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 	if (IS_ERR(req))
 		return req;
 
+	req->tc.zc = false;
+	req->rc.zc = false;
+
 	if (signal_pending(current)) {
 		sigpending = 1;
 		clear_thread_flag(TIF_SIGPENDING);
@@ -778,6 +781,9 @@ static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type,
 	if (IS_ERR(req))
 		return req;
 
+	req->tc.zc = true;
+	req->rc.zc = true;
+
 	if (signal_pending(current)) {
 		sigpending = 1;
 		clear_thread_flag(TIF_SIGPENDING);
-- 
2.30.2