cifs: change iface_list from array to sorted linked list

A server's published interface list can change over time, and needs
to be updated. We've storing iface_list as a simple array, which
makes it difficult to manipulate an existing list.

With this change, iface_list is modified into a linked list of
interfaces, which is kept sorted by speed.

Also added a reference counter for an iface entry, so that each
channel can maintain a backpointer to the iface and drop it
easily when needed.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 53 insertions, 1 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index e7737166e5b8..7fc2addc95a3 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -933,15 +933,67 @@ static inline void cifs_set_net_ns(struct TCP_Server_Info *srv, struct net *net)
 #endif
 
 struct cifs_server_iface {
+	struct list_head iface_head;
+	struct kref refcount;
 	size_t speed;
 	unsigned int rdma_capable : 1;
 	unsigned int rss_capable : 1;
+	unsigned int is_active : 1; /* unset if non existent */
 	struct sockaddr_storage sockaddr;
 };
 
+/* release iface when last ref is dropped */
+static inline void
+release_iface(struct kref *ref)
+{
+	struct cifs_server_iface *iface = container_of(ref,
+						       struct cifs_server_iface,
+						       refcount);
+	list_del_init(&iface->iface_head);
+	kfree(iface);
+}
+
+/*
+ * compare two interfaces a and b
+ * return 0 if everything matches.
+ * return 1 if a has higher link speed, or rdma capable, or rss capable
+ * return -1 otherwise.
+ */
+static inline int
+iface_cmp(struct cifs_server_iface *a, struct cifs_server_iface *b)
+{
+	int cmp_ret = 0;
+
+	WARN_ON(!a || !b);
+	if (a->speed == b->speed) {
+		if (a->rdma_capable == b->rdma_capable) {
+			if (a->rss_capable == b->rss_capable) {
+				cmp_ret = memcmp(&a->sockaddr, &b->sockaddr,
+						 sizeof(a->sockaddr));
+				if (!cmp_ret)
+					return 0;
+				else if (cmp_ret > 0)
+					return 1;
+				else
+					return -1;
+			} else if (a->rss_capable > b->rss_capable)
+				return 1;
+			else
+				return -1;
+		} else if (a->rdma_capable > b->rdma_capable)
+			return 1;
+		else
+			return -1;
+	} else if (a->speed > b->speed)
+		return 1;
+	else
+		return -1;
+}
+
 struct cifs_chan {
 	unsigned int in_reconnect : 1; /* if session setup in progress for this channel */
 	struct TCP_Server_Info *server;
+	struct cifs_server_iface *iface; /* interface in use */
 	__u8 signkey[SMB3_SIGN_KEY_SIZE];
 };
 
@@ -993,7 +1045,7 @@ struct cifs_ses {
 	 */
 	spinlock_t iface_lock;
 	/* ========= begin: protected by iface_lock ======== */
-	struct cifs_server_iface *iface_list;
+	struct list_head iface_list;
 	size_t iface_count;
 	unsigned long iface_last_update; /* jiffies */
 	/* ========= end: protected by iface_lock ======== */