drm/i915: Attempt to prefault user pages for pread/pwrite

... in the hope that it makes the atomic fast paths more likely.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 942e4b3..b44c09a 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -265,19 +265,14 @@ fast_shmem_read(struct page **pages,
                char __user *data,
                int length)
 {
-       char __iomem *vaddr;
        int unwritten;
+       char *vaddr;
 
        vaddr = kmap_atomic(pages[page_base >> PAGE_SHIFT], KM_USER0);
-       if (vaddr == NULL)
-               return -ENOMEM;
        unwritten = __copy_to_user_inatomic(data, vaddr + page_offset, length);
        kunmap_atomic(vaddr, KM_USER0);
 
-       if (unwritten)
-               return -EFAULT;
-
-       return 0;
+       return unwritten ? -EFAULT : 0;
 }
 
 static int i915_gem_object_needs_bit17_swizzle(struct drm_gem_object *obj)
@@ -602,6 +597,13 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
                goto out;
        }
 
+       ret = fault_in_pages_writeable((char __user *)(uintptr_t)args->data_ptr,
+                                      args->size);
+       if (ret) {
+               ret = -EFAULT;
+               goto out;
+       }
+
        if (i915_gem_object_needs_bit17_swizzle(obj)) {
                ret = i915_gem_shmem_pread_slow(dev, obj, args, file_priv);
        } else {
@@ -668,18 +670,14 @@ fast_shmem_write(struct page **pages,
                 char __user *data,
                 int length)
 {
-       char __iomem *vaddr;
-       unsigned long unwritten;
+       int unwritten;
+       char *vaddr;
 
        vaddr = kmap_atomic(pages[page_base >> PAGE_SHIFT], KM_USER0);
-       if (vaddr == NULL)
-               return -ENOMEM;
        unwritten = __copy_from_user_inatomic(vaddr + page_offset, data, length);
        kunmap_atomic(vaddr, KM_USER0);
 
-       if (unwritten)
-               return -EFAULT;
-       return 0;
+       return unwritten ? -EFAULT : 0;
 }
 
 /**
@@ -1078,6 +1076,13 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                goto out;
        }
 
+       ret = fault_in_pages_readable((char __user *)(uintptr_t)args->data_ptr,
+                                     args->size);
+       if (ret) {
+               ret = -EFAULT;
+               goto out;
+       }
+
        /* We can only do the GTT pwrite on untiled buffers, as otherwise
         * it would end up going through the fenced access, and we'll get
         * different detiling behavior between reading and writing.