dma-buf/fence: make fence context 64 bit v2

Fence contexts are created on the fly (for example) by the GPU scheduler used
in the amdgpu driver as a result of an userspace request. Because of this
userspace could in theory force a wrap around of the 32bit context number
if it doesn't behave well.

Avoid this by increasing the context number to 64bits. This way even when
userspace manages to allocate a billion contexts per second it takes more
than 500 years for the context number to wrap around.

v2: fix printf formats as well.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1464786612-5010-2-git-send-email-deathsimple@vodafone.de
diff --git a/include/linux/fence.h b/include/linux/fence.h
index 2b17698..18a97c6 100644
--- a/include/linux/fence.h
+++ b/include/linux/fence.h
@@ -75,7 +75,8 @@
 	struct rcu_head rcu;
 	struct list_head cb_list;
 	spinlock_t *lock;
-	unsigned context, seqno;
+	u64 context;
+	unsigned seqno;
 	unsigned long flags;
 	ktime_t timestamp;
 	int status;
@@ -178,7 +179,7 @@
 };
 
 void fence_init(struct fence *fence, const struct fence_ops *ops,
-		spinlock_t *lock, unsigned context, unsigned seqno);
+		spinlock_t *lock, u64 context, unsigned seqno);
 
 void fence_release(struct kref *kref);
 void fence_free(struct fence *fence);
@@ -352,27 +353,27 @@
 	return ret < 0 ? ret : 0;
 }
 
-unsigned fence_context_alloc(unsigned num);
+u64 fence_context_alloc(unsigned num);
 
 #define FENCE_TRACE(f, fmt, args...) \
 	do {								\
 		struct fence *__ff = (f);				\
 		if (config_enabled(CONFIG_FENCE_TRACE))			\
-			pr_info("f %u#%u: " fmt,			\
+			pr_info("f %llu#%u: " fmt,			\
 				__ff->context, __ff->seqno, ##args);	\
 	} while (0)
 
 #define FENCE_WARN(f, fmt, args...) \
 	do {								\
 		struct fence *__ff = (f);				\
-		pr_warn("f %u#%u: " fmt, __ff->context, __ff->seqno,	\
+		pr_warn("f %llu#%u: " fmt, __ff->context, __ff->seqno,	\
 			 ##args);					\
 	} while (0)
 
 #define FENCE_ERR(f, fmt, args...) \
 	do {								\
 		struct fence *__ff = (f);				\
-		pr_err("f %u#%u: " fmt, __ff->context, __ff->seqno,	\
+		pr_err("f %llu#%u: " fmt, __ff->context, __ff->seqno,	\
 			##args);					\
 	} while (0)