Affinity shared memory area must be at least a page

If the system page size is greater than 4kB (or 32kB in the case of
BIGNUMA), then the affinity code will fail to initialise.

Ensure the shared memory area is at least one page in size.

driver/others/init.c

@@ -555,24 +555,24 @@ static inline int is_dead(int id) {
 }
 
 static void open_shmem(void) {
+  int shm_size = 4096;
+
+#if defined(BIGNUMA)
+  // raised to 32768, enough for 128 nodes and 1024 cups
+  shm_size = 32*1024;
+#endif
+
+  // needs to be at least one page
+  shm_size = MAX(getpagesize(), shm_size);
 
   int try = 0;
 
   do {
 
-#if defined(BIGNUMA)
-    // raised to 32768, enough for 128 nodes and 1024 cups
-    shmid = shmget(SH_MAGIC, 32768, 0666);
-#else
-    shmid = shmget(SH_MAGIC, 4096, 0666);
-#endif
+    shmid = shmget(SH_MAGIC, shm_size, 0666);
 
     if (shmid == -1) {
-#if defined(BIGNUMA)
-      shmid = shmget(SH_MAGIC, 32768, IPC_CREAT | 0666);
-#else
-      shmid = shmget(SH_MAGIC, 4096, IPC_CREAT | 0666);
-#endif
+      shmid = shmget(SH_MAGIC, shm_size, IPC_CREAT | 0666);
     }
 
     try ++;