Reserve the last MAX_COMPOUND credits for any request asking for >1 credit.
This is to prevent future compound requests from becoming starved while waiting
for potentially many requests is there is a large number of concurrent
singe-credit requests.
Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
---
fs/cifs/transport.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index baf15194aa3d..4ff832fce2e9 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -520,6 +520,29 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
}
/*
+ * For normal commands, reserve the last MAX_COMPOUND
+ * credits to compound requests.
+ * Otherwise these compounds could be permanently
+ * starved for credits by single-credit requests.
+ *
+ * To prevent spinning CPU, block this thread until
+ * there are >MAX_COMPOUND credits available.
+ */
+ if (!optype && num_credits == 1 &&
+ *credits <= MAX_COMPOUND) {
+ spin_unlock(&server->req_lock);
+ cifs_num_waiters_inc(server);
+ rc = wait_event_killable(server->request_q,
+ has_credits(server, credits,
+ MAX_COMPOUND + 1));
+ cifs_num_waiters_dec(server);
+ if (rc)
+ return rc;
+ spin_lock(&server->req_lock);
+ continue;
+ }
+
+ /*
* Can not count locking commands against total
* as they are allowed to block on server.
*/
--
2.13.6
