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>

Author: sprasad-microsoft

fs/cifs/cifs_debug.c

@@ -162,6 +162,8 @@ cifs_dump_iface(struct seq_file *m, struct cifs_server_iface *iface)
 		seq_printf(m, "\t\tIPv4: %pI4\n", &ipv4->sin_addr);
 	else if (iface->sockaddr.ss_family == AF_INET6)
 		seq_printf(m, "\t\tIPv6: %pI6\n", &ipv6->sin6_addr);
+	if (!iface->is_active)
+		seq_puts(m, "\t\t[for-cleanup]\n");
 }
 
 static int cifs_debug_files_proc_show(struct seq_file *m, void *v)
@@ -221,6 +223,7 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 	struct TCP_Server_Info *server;
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon;
+	struct cifs_server_iface *iface;
 	int c, i, j;
 
 	seq_puts(m,
@@ -456,11 +459,10 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 			if (ses->iface_count)
 				seq_printf(m, "\n\n\tServer interfaces: %zu",
 					   ses->iface_count);
-			for (j = 0; j < ses->iface_count; j++) {
-				struct cifs_server_iface *iface;
-
-				iface = &ses->iface_list[j];
-				seq_printf(m, "\n\t%d)", j+1);
+			j = 0;
+			list_for_each_entry(iface, &ses->iface_list,
+						 iface_head) {
+				seq_printf(m, "\n\t%d)", ++j);
 				cifs_dump_iface(m, iface);
 				if (is_ses_using_iface(ses, iface))
 					seq_puts(m, "\t\t[CONNECTED]\n");

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 ======== */

fs/cifs/connect.c

@@ -1894,9 +1894,11 @@ void cifs_put_smb_ses(struct cifs_ses *ses)
 		int i;
 
 		for (i = 1; i < chan_count; i++) {
-			spin_unlock(&ses->chan_lock);
+			if (ses->chans[i].iface) {
+				kref_put(&ses->chans[i].iface->refcount, release_iface);
+				ses->chans[i].iface = NULL;
+			}
 			cifs_put_tcp_session(ses->chans[i].server, 0);
-			spin_lock(&ses->chan_lock);
 			ses->chans[i].server = NULL;
 		}
 	}

fs/cifs/misc.c

@@ -75,6 +75,7 @@ sesInfoAlloc(void)
 		INIT_LIST_HEAD(&ret_buf->tcon_list);
 		mutex_init(&ret_buf->session_mutex);
 		spin_lock_init(&ret_buf->iface_lock);
+		INIT_LIST_HEAD(&ret_buf->iface_list);
 		spin_lock_init(&ret_buf->chan_lock);
 	}
 	return ret_buf;
@@ -83,6 +84,8 @@ sesInfoAlloc(void)
 void
 sesInfoFree(struct cifs_ses *buf_to_free)
 {
+	struct cifs_server_iface *iface = NULL, *niface = NULL;
+
 	if (buf_to_free == NULL) {
 		cifs_dbg(FYI, "Null buffer passed to sesInfoFree\n");
 		return;
@@ -96,7 +99,11 @@ sesInfoFree(struct cifs_ses *buf_to_free)
 	kfree(buf_to_free->user_name);
 	kfree(buf_to_free->domainName);
 	kfree_sensitive(buf_to_free->auth_key.response);
-	kfree(buf_to_free->iface_list);
+	spin_lock(&buf_to_free->iface_lock);
+	list_for_each_entry_safe(iface, niface, &buf_to_free->iface_list,
+				 iface_head)
+		kref_put(&iface->refcount, release_iface);
+	spin_unlock(&buf_to_free->iface_lock);
 	kfree_sensitive(buf_to_free);
 }
 

fs/cifs/sess.c

@@ -58,7 +58,7 @@ bool is_ses_using_iface(struct cifs_ses *ses, struct cifs_server_iface *iface)
 
 	spin_lock(&ses->chan_lock);
 	for (i = 0; i < ses->chan_count; i++) {
-		if (is_server_using_iface(ses->chans[i].server, iface)) {
+		if (ses->chans[i].iface == iface) {
 			spin_unlock(&ses->chan_lock);
 			return true;
 		}
@@ -151,11 +151,9 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 {
 	int old_chan_count, new_chan_count;
 	int left;
-	int i = 0;
 	int rc = 0;
 	int tries = 0;
-	struct cifs_server_iface *ifaces = NULL;
-	size_t iface_count;
+	struct cifs_server_iface *iface = NULL, *niface = NULL;
 
 	spin_lock(&ses->chan_lock);
 
@@ -184,33 +182,17 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 	}
 	spin_unlock(&ses->chan_lock);
 
-	/*
-	 * Make a copy of the iface list at the time and use that
-	 * instead so as to not hold the iface spinlock for opening
-	 * channels
-	 */
-	spin_lock(&ses->iface_lock);
-	iface_count = ses->iface_count;
-	if (iface_count <= 0) {
-		spin_unlock(&ses->iface_lock);
-		cifs_dbg(VFS, "no iface list available to open channels\n");
-		return 0;
-	}
-	ifaces = kmemdup(ses->iface_list, iface_count*sizeof(*ifaces),
-			 GFP_ATOMIC);
-	if (!ifaces) {
-		spin_unlock(&ses->iface_lock);
-		return 0;
-	}
-	spin_unlock(&ses->iface_lock);
-
 	/*
 	 * Keep connecting to same, fastest, iface for all channels as
 	 * long as its RSS. Try next fastest one if not RSS or channel
 	 * creation fails.
 	 */
+	spin_lock(&ses->iface_lock);
+	iface = list_first_entry(&ses->iface_list, struct cifs_server_iface,
+				 iface_head);
+	spin_unlock(&ses->iface_lock);
+
 	while (left > 0) {
-		struct cifs_server_iface *iface;
 
 		tries++;
 		if (tries > 3*ses->chan_max) {
@@ -219,27 +201,46 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 			break;
 		}
 
-		iface = &ifaces[i];
-		if (is_ses_using_iface(ses, iface) && !iface->rss_capable) {
-			i = (i+1) % iface_count;
-			continue;
+		spin_lock(&ses->iface_lock);
+		if (!ses->iface_count) {
+			spin_unlock(&ses->iface_lock);
+			break;
 		}
 
-		rc = cifs_ses_add_channel(cifs_sb, ses, iface);
-		if (rc) {
-			cifs_dbg(FYI, "failed to open extra channel on iface#%d rc=%d\n",
-				 i, rc);
-			i = (i+1) % iface_count;
-			continue;
+		list_for_each_entry_safe_from(iface, niface, &ses->iface_list,
+				    iface_head) {
+			/* skip ifaces that are unusable */
+			if (!iface->is_active ||
+			    (is_ses_using_iface(ses, iface) &&
+			     !iface->rss_capable)) {
+				continue;
+			}
+
+			/* take ref before unlock */
+			kref_get(&iface->refcount);
+
+			spin_unlock(&ses->iface_lock);
+			rc = cifs_ses_add_channel(cifs_sb, ses, iface);
+			spin_lock(&ses->iface_lock);
+
+			if (rc) {
+				cifs_dbg(VFS, "failed to open extra channel on iface:%pIS rc=%d\n",
+					 &iface->sockaddr,
+					 rc);
+				kref_put(&iface->refcount, release_iface);
+				continue;
+			}
+
+			cifs_dbg(FYI, "successfully opened new channel on iface:%pIS\n",
+				 &iface->sockaddr);
+			break;
 		}
+		spin_unlock(&ses->iface_lock);
 
-		cifs_dbg(FYI, "successfully opened new channel on iface#%d\n",
-			 i);
 		left--;
 		new_chan_count++;
 	}
 
-	kfree(ifaces);
 	return new_chan_count - old_chan_count;
 }
 
@@ -355,6 +356,7 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 		spin_unlock(&ses->chan_lock);
 		goto out;
 	}
+	chan->iface = iface;
 	ses->chan_count++;
 	atomic_set(&ses->chan_seq, 0);