i915: cleanup coding horrors in i915_gem_gtt_pwrite()

Yes, this will probably be switched over to a cleaner model anyway, but
in the meantime I don't want to see the 'unused variable' warnings that
come from the disgusting #ifdef code.  Make the special case be a nice
inlien function of its own, clean up the code, and make the warning go
away.

I wish people didn't write code that gets (valid) warnings from the
compiler, but I'll limit my fixes to code that I actually care about (in
this case just because I see the warning and it annoys me).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9ac73dd1b422db554758061d7d8786403bf64b9e..49c5a1798ac4db409a0072daa7923dee89dce277 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -171,6 +171,36 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
        return 0;
 }
 
+/*
+ * Try to write quickly with an atomic kmap. Return true on success.
+ *
+ * If this fails (which includes a partial write), we'll redo the whole
+ * thing with the slow version.
+ *
+ * This is a workaround for the low performance of iounmap (approximate
+ * 10% cpu cost on normal 3D workloads).  kmap_atomic on HIGHMEM kernels
+ * happens to let us map card memory without taking IPIs.  When the vmap
+ * rework lands we should be able to dump this hack.
+ */
+static inline int fast_user_write(unsigned long pfn, char __user *user_data, int l)
+{
+#ifdef CONFIG_HIGHMEM
+       unsigned long unwritten;
+       char *vaddr_atomic;
+
+       vaddr_atomic = kmap_atomic_pfn(pfn, KM_USER0);
+#if WATCH_PWRITE
+       DRM_INFO("pwrite i %d o %d l %d pfn %ld vaddr %p\n",
+                i, o, l, pfn, vaddr_atomic);
+#endif
+       unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + o, user_data, l);
+       kunmap_atomic(vaddr_atomic, KM_USER0);
+       return !unwritten;
+#else
+       return 0;
+#endif
+}
+
 static int
 i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
                    struct drm_i915_gem_pwrite *args,
@@ -180,12 +210,7 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
        ssize_t remain;
        loff_t offset;
        char __user *user_data;
-       char __iomem *vaddr;
-       char *vaddr_atomic;
-       int i, o, l;
        int ret = 0;
-       unsigned long pfn;
-       unsigned long unwritten;
 
        user_data = (char __user *) (uintptr_t) args->data_ptr;
        remain = args->size;
@@ -209,6 +234,9 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
        obj_priv->dirty = 1;
 
        while (remain > 0) {
+               unsigned long pfn;
+               int i, o, l;
+
                /* Operation in this page
                 *
                 * i = page number
@@ -223,25 +251,10 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
 
                pfn = (dev->agp->base >> PAGE_SHIFT) + i;
 
-#ifdef CONFIG_HIGHMEM
-               /* This is a workaround for the low performance of iounmap
-                * (approximate 10% cpu cost on normal 3D workloads).
-                * kmap_atomic on HIGHMEM kernels happens to let us map card
-                * memory without taking IPIs.  When the vmap rework lands
-                * we should be able to dump this hack.
-                */
-               vaddr_atomic = kmap_atomic_pfn(pfn, KM_USER0);
-#if WATCH_PWRITE
-               DRM_INFO("pwrite i %d o %d l %d pfn %ld vaddr %p\n",
-                        i, o, l, pfn, vaddr_atomic);
-#endif
-               unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + o,
-                                                             user_data, l);
-               kunmap_atomic(vaddr_atomic, KM_USER0);
+               if (!fast_user_write(pfn, user_data, l)) {
+                       unsigned long unwritten;
+                       char __iomem *vaddr;
 
-               if (unwritten)
-#endif /* CONFIG_HIGHMEM */
-               {
                        vaddr = ioremap_wc(pfn << PAGE_SHIFT, PAGE_SIZE);
 #if WATCH_PWRITE
                        DRM_INFO("pwrite slow i %d o %d l %d "