cifs: sort interface list by speed

New channels are going to be opened by walking the list sequentially,
so by sorting it we will connect to the fastest interfaces first.

Signed-off-by: Aurelien Aptel <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/cifs/smb2ops.c

···
 #include <linux/falloc.h>
 #include <linux/scatterlist.h>
 #include <linux/uuid.h>
+#include <linux/sort.h>
 #include <crypto/aead.h>
 #include "cifsglob.h"
 #include "smb2pdu.h"
···
 	return rc;
 }
 
+static int compare_iface(const void *ia, const void *ib)
+{
+	const struct cifs_server_iface *a = (struct cifs_server_iface *)ia;
+	const struct cifs_server_iface *b = (struct cifs_server_iface *)ib;
+
+	return a->speed == b->speed ? 0 : (a->speed > b->speed ? -1 : 1);
+}
 
 static int
 SMB3_request_interfaces(const unsigned int xid, struct cifs_tcon *tcon)
···
 				     &iface_list, &iface_count);
 	if (rc)
 		goto out;
+
+	/* sort interfaces from fastest to slowest */
+	sort(iface_list, iface_count, sizeof(*iface_list), compare_iface, NULL);
 
 	spin_lock(&ses->iface_lock);
 	kfree(ses->iface_list);