drm/i915: Ditch the i915_gem_ww_ctx loop member

It's only used by the for_i915_gem_ww() macro and we can use
the (typically) on-stack _err variable in its place.

v2:
- Don't clear the _err variable when entering the loop
  (Matthew Auld, Maarten Lankhorst).
- Use parentheses around the _err macro argument.
- Fix up comment.

Cc: Matthew Auld <matthew.william.auld@gmail.com>
Suggested-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210816171444.105469-1-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/i915_gem_ww.h

@@ -11,8 +11,7 @@ struct i915_gem_ww_ctx {
 	struct ww_acquire_ctx ctx;
 	struct list_head obj_list;
 	struct drm_i915_gem_object *contended;
-	unsigned short intr;
-	unsigned short loop;
+	bool intr;
 };
 
 void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
@@ -20,31 +19,23 @@ void i915_gem_ww_ctx_fini(struct i915_gem_ww_ctx *ctx);
 int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ctx);
 void i915_gem_ww_unlock_single(struct drm_i915_gem_object *obj);
 
-/* Internal functions used by the inlines! Don't use. */
+/* Internal function used by the inlines! Don't use. */
 static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
 {
-	ww->loop = 0;
 	if (err == -EDEADLK) {
 		err = i915_gem_ww_ctx_backoff(ww);
 		if (!err)
-			ww->loop = 1;
+			err = -EDEADLK;
 	}
 
-	if (!ww->loop)
+	if (err != -EDEADLK)
 		i915_gem_ww_ctx_fini(ww);
 
 	return err;
 }
 
-static inline void
-__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
-{
-	i915_gem_ww_ctx_init(ww, intr);
-	ww->loop = 1;
-}
-
 #define for_i915_gem_ww(_ww, _err, _intr)			  \
-	for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop;	\
-	     _err = __i915_gem_ww_fini(_ww, _err))
-
+	for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
+	     (_err) == -EDEADLK;				  \
+	     (_err) = __i915_gem_ww_fini(_ww, _err))
 #endif