drm/i915: rearrange mutex acquisition for pread

... to avoid the double acquisition along fast[er] paths.

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 1177ff5779141b07e36223b3682234b1753f967c..efc6a4e3b1d213df5fac179a11b9440ce0c21b45 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -265,14 +265,14 @@ fast_shmem_read(struct page **pages,
                char __user *data,
                int length)
 {
-       int unwritten;
        char *vaddr;
+       int ret;
 
        vaddr = kmap_atomic(pages[page_base >> PAGE_SHIFT], KM_USER0);
-       unwritten = __copy_to_user_inatomic(data, vaddr + page_offset, length);
+       ret = __copy_to_user_inatomic(data, vaddr + page_offset, length);
        kunmap_atomic(vaddr, KM_USER0);
 
-       return unwritten ? -EFAULT : 0;
+       return ret;
 }
 
 static int i915_gem_object_needs_bit17_swizzle(struct drm_gem_object *obj)
@@ -366,24 +366,10 @@ i915_gem_shmem_pread_fast(struct drm_device *dev, struct drm_gem_object *obj,
        loff_t offset, page_base;
        char __user *user_data;
        int page_offset, page_length;
-       int ret;
 
        user_data = (char __user *) (uintptr_t) args->data_ptr;
        remain = args->size;
 
-       ret = i915_mutex_lock_interruptible(dev);
-       if (ret)
-               return ret;
-
-       ret = i915_gem_object_get_pages(obj, 0);
-       if (ret != 0)
-               goto fail_unlock;
-
-       ret = i915_gem_object_set_cpu_read_domain_range(obj, args->offset,
-                                                       args->size);
-       if (ret != 0)
-               goto fail_put_pages;
-
        obj_priv = to_intel_bo(obj);
        offset = args->offset;
 
@@ -400,23 +386,17 @@ i915_gem_shmem_pread_fast(struct drm_device *dev, struct drm_gem_object *obj,
                if ((page_offset + remain) > PAGE_SIZE)
                        page_length = PAGE_SIZE - page_offset;
 
-               ret = fast_shmem_read(obj_priv->pages,
-                                     page_base, page_offset,
-                                     user_data, page_length);
-               if (ret)
-                       goto fail_put_pages;
+               if (fast_shmem_read(obj_priv->pages,
+                                   page_base, page_offset,
+                                   user_data, page_length))
+                       return -EFAULT;
 
                remain -= page_length;
                user_data += page_length;
                offset += page_length;
        }
 
-fail_put_pages:
-       i915_gem_object_put_pages(obj);
-fail_unlock:
-       mutex_unlock(&dev->struct_mutex);
-
-       return ret;
+       return 0;
 }
 
 static int
@@ -477,33 +457,28 @@ i915_gem_shmem_pread_slow(struct drm_device *dev, struct drm_gem_object *obj,
        last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
        num_pages = last_data_page - first_data_page + 1;
 
-       user_pages = drm_calloc_large(num_pages, sizeof(struct page *));
+       user_pages = drm_malloc_ab(num_pages, sizeof(struct page *));
        if (user_pages == NULL)
                return -ENOMEM;
 
+       mutex_unlock(&dev->struct_mutex);
        down_read(&mm->mmap_sem);
        pinned_pages = get_user_pages(current, mm, (uintptr_t)args->data_ptr,
                                      num_pages, 1, 0, user_pages, NULL);
        up_read(&mm->mmap_sem);
+       mutex_lock(&dev->struct_mutex);
        if (pinned_pages < num_pages) {
                ret = -EFAULT;
-               goto fail_put_user_pages;
+               goto out;
        }
 
-       do_bit17_swizzling = i915_gem_object_needs_bit17_swizzle(obj);
-
-       ret = i915_mutex_lock_interruptible(dev);
-       if (ret)
-               goto fail_put_user_pages;
-
-       ret = i915_gem_object_get_pages_or_evict(obj);
+       ret = i915_gem_object_set_cpu_read_domain_range(obj,
+                                                       args->offset,
+                                                       args->size);
        if (ret)
-               goto fail_unlock;
+               goto out;
 
-       ret = i915_gem_object_set_cpu_read_domain_range(obj, args->offset,
-                                                       args->size);
-       if (ret != 0)
-               goto fail_put_pages;
+       do_bit17_swizzling = i915_gem_object_needs_bit17_swizzle(obj);
 
        obj_priv = to_intel_bo(obj);
        offset = args->offset;
@@ -548,11 +523,7 @@ i915_gem_shmem_pread_slow(struct drm_device *dev, struct drm_gem_object *obj,
                offset += page_length;
        }
 
-fail_put_pages:
-       i915_gem_object_put_pages(obj);
-fail_unlock:
-       mutex_unlock(&dev->struct_mutex);
-fail_put_user_pages:
+out:
        for (i = 0; i < pinned_pages; i++) {
                SetPageDirty(user_pages[i]);
                page_cache_release(user_pages[i]);
@@ -581,6 +552,12 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
                return -ENOENT;
        obj_priv = to_intel_bo(obj);
 
+       ret = i915_mutex_lock_interruptible(dev);
+       if (ret) {
+               drm_gem_object_unreference_unlocked(obj);
+               return ret;
+       }
+
        /* Bounds check source.  */
        if (args->offset > obj->size || args->size > obj->size - args->offset) {
                ret = -EINVAL;
@@ -604,17 +581,27 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
                goto out;
        }
 
-       if (i915_gem_object_needs_bit17_swizzle(obj)) {
-               ret = i915_gem_shmem_pread_slow(dev, obj, args, file_priv);
-       } else {
+       ret = i915_gem_object_get_pages_or_evict(obj);
+       if (ret)
+               goto out;
+
+       ret = i915_gem_object_set_cpu_read_domain_range(obj,
+                                                       args->offset,
+                                                       args->size);
+       if (ret)
+               goto out_put;
+
+       ret = -EFAULT;
+       if (!i915_gem_object_needs_bit17_swizzle(obj))
                ret = i915_gem_shmem_pread_fast(dev, obj, args, file_priv);
-               if (ret != 0)
-                       ret = i915_gem_shmem_pread_slow(dev, obj, args,
-                                                       file_priv);
-       }
+       if (ret == -EFAULT)
+               ret = i915_gem_shmem_pread_slow(dev, obj, args, file_priv);
 
+out_put:
+       i915_gem_object_put_pages(obj);
 out:
-       drm_gem_object_unreference_unlocked(obj);
+       drm_gem_object_unreference(obj);
+       mutex_unlock(&dev->struct_mutex);
        return ret;
 }
 
@@ -908,7 +895,7 @@ i915_gem_shmem_pwrite_slow(struct drm_device *dev, struct drm_gem_object *obj,
        last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
        num_pages = last_data_page - first_data_page + 1;
 
-       user_pages = drm_calloc_large(num_pages, sizeof(struct page *));
+       user_pages = drm_malloc_ab(num_pages, sizeof(struct page *));
        if (user_pages == NULL)
                return -ENOMEM;