+static DEFINE_RAW_SPINLOCK(buffer_lock);
+
+/* increase and wrap the start pointer, returning the old value */
+static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a)
+{
+ int old;
+ int new;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&buffer_lock, flags);
+
+ old = atomic_read(&prz->buffer->start);
+ new = old + a;
+ while (unlikely(new > prz->buffer_size))
+ new -= prz->buffer_size;
+ atomic_set(&prz->buffer->start, new);
+
+ raw_spin_unlock_irqrestore(&buffer_lock, flags);
+
+ return old;
+}
+
+/* increase the size counter until it hits the max size */
+static void buffer_size_add_locked(struct persistent_ram_zone *prz, size_t a)
+{
+ size_t old;
+ size_t new;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&buffer_lock, flags);
+
+ old = atomic_read(&prz->buffer->size);
+ if (old == prz->buffer_size)
+ goto exit;
+
+ new = old + a;
+ if (new > prz->buffer_size)
+ new = prz->buffer_size;
+ atomic_set(&prz->buffer->size, new);
+
+exit:
+ raw_spin_unlock_irqrestore(&buffer_lock, flags);
+}
+
+static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic;
+static void (*buffer_size_add)(struct persistent_ram_zone *, size_t) = buffer_size_add_atomic;
+