CIFS: Introduce credit-based flow control

and send no more than credits value requests at once. For SMB/CIFS
it's trivial: increment this value by receiving any message and
decrement by sending one.

Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 703ef5c6fdb1..c273c12de98e 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -690,3 +690,22 @@ backup_cred(struct cifs_sb_info *cifs_sb)
 
         return false;
 }
+
+void
+cifs_add_credits(struct TCP_Server_Info *server, const unsigned int add)
+{
+        spin_lock(&server->req_lock);
+        server->credits += add;
+        server->in_flight--;
+        spin_unlock(&server->req_lock);
+        wake_up(&server->request_q);
+}
+
+void
+cifs_set_credits(struct TCP_Server_Info *server, const int val)
+{
+        spin_lock(&server->req_lock);
+        server->credits = val;
+        server->oplocks = val > 1 ? enable_oplocks : false;
+        spin_unlock(&server->req_lock);
+}