[PATCH 24/30] drm/i915: Refactor pwrite/pread to use single copy of get_user_pages

[Chris Wilson <chris@chris-wilson.co.uk>]

Replace the three nearly identical copies of the code with a single
function. And take advantage of the opportunity to do some
micro-optimisation: avoid the vmalloc if at all possible and also avoid
dropping the lock unless we are forced to acquire the mm semaphore.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c |  132 ++++++++++++++++++++++-----------------
 1 files changed, 75 insertions(+), 57 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 33830c9..0028f3b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -257,6 +257,56 @@ static int i915_gem_object_needs_bit17_swizzle(struct drm_i915_gem_object *obj)
 		obj->tiling_mode != I915_TILING_NONE;
 }
 
+static int
+i915_gem_get_user_pages(struct drm_device *dev,
+			unsigned long addr,
+			bool write,
+			int *num_pages,
+			struct page ***pages_out)
+{
+	struct page **pages;
+	int pinned, ret;
+	int n = *num_pages;
+
+	pages = kmalloc(n*sizeof(struct page *),
+			GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+	if (pages == NULL) {
+		pages = drm_malloc_ab(n, sizeof(struct page *));
+		if (pages == NULL) {
+			*pages_out = NULL;
+			*num_pages = 0;
+			return -ENOMEM;
+		}
+	}
+
+	pinned = __get_user_pages_fast(addr, n, write, pages);
+	if (pinned < n) {
+		struct mm_struct *mm = current->mm;
+
+		mutex_unlock(&dev->struct_mutex);
+		down_read(&mm->mmap_sem);
+		ret = get_user_pages(current, mm,
+				     addr + (pinned << PAGE_SHIFT),
+				     n - pinned,
+				     write, 0,
+				     pages + pinned,
+				     NULL);
+		up_read(&mm->mmap_sem);
+		mutex_lock(&dev->struct_mutex);
+		if (ret > 0)
+			pinned += ret;
+	}
+
+	ret = 0;
+	if (pinned < n)
+		ret = -EFAULT;
+
+	*num_pages = pinned;
+	*pages_out = pages;
+	return ret;
+}
+
+
 static inline void
 slow_shmem_copy(struct page *dst_page,
 		int dst_offset,
@@ -398,11 +448,11 @@ i915_gem_shmem_pread_slow(struct drm_device *dev,
 			  struct drm_file *file)
 {
 	struct address_space *mapping = obj->base.filp->f_path.dentry->d_inode->i_mapping;
-	struct mm_struct *mm = current->mm;
 	struct page **user_pages;
 	ssize_t remain;
-	loff_t offset, pinned_pages, i;
-	loff_t first_data_page, last_data_page, num_pages;
+	loff_t offset;
+	loff_t first_data_page, last_data_page;
+	int num_pages, i;
 	int shmem_page_offset;
 	int data_page_index, data_page_offset;
 	int page_length;
@@ -420,20 +470,10 @@ i915_gem_shmem_pread_slow(struct drm_device *dev,
 	last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
 	num_pages = last_data_page - first_data_page + 1;
 
-	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;
+	ret = i915_gem_get_user_pages(dev, data_ptr, true,
+				      &num_pages, &user_pages);
+	if (ret)
 		goto out;
-	}
 
 	ret = i915_gem_object_set_cpu_read_domain_range(obj,
 							args->offset,
@@ -494,7 +534,7 @@ i915_gem_shmem_pread_slow(struct drm_device *dev,
 	}
 
 out:
-	for (i = 0; i < pinned_pages; i++) {
+	for (i = 0; i < num_pages; i++) {
 		SetPageDirty(user_pages[i]);
 		mark_page_accessed(user_pages[i]);
 		page_cache_release(user_pages[i]);
@@ -679,10 +719,9 @@ i915_gem_gtt_pwrite_slow(struct drm_device *dev,
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	ssize_t remain;
 	loff_t gtt_page_base, offset;
-	loff_t first_data_page, last_data_page, num_pages;
-	loff_t pinned_pages, i;
+	loff_t first_data_page, last_data_page;
+	int num_pages, i;
 	struct page **user_pages;
-	struct mm_struct *mm = current->mm;
 	int gtt_page_offset, data_page_offset, data_page_index, page_length;
 	int ret;
 	uint64_t data_ptr = args->data_ptr;
@@ -697,28 +736,18 @@ i915_gem_gtt_pwrite_slow(struct drm_device *dev,
 	last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
 	num_pages = last_data_page - first_data_page + 1;
 
-	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, 0, 0, user_pages, NULL);
-	up_read(&mm->mmap_sem);
-	mutex_lock(&dev->struct_mutex);
-	if (pinned_pages < num_pages) {
-		ret = -EFAULT;
-		goto out_unpin_pages;
-	}
+	ret = i915_gem_get_user_pages(dev, data_ptr, false,
+				      &num_pages, &user_pages);
+	if (ret)
+		goto out;
 
 	ret = i915_gem_object_set_to_gtt_domain(obj, true);
 	if (ret)
-		goto out_unpin_pages;
+		goto out;
 
 	ret = i915_gem_object_put_fence(obj);
 	if (ret)
-		goto out_unpin_pages;
+		goto out;
 
 	offset = obj->gtt_offset + args->offset;
 
@@ -753,8 +782,8 @@ i915_gem_gtt_pwrite_slow(struct drm_device *dev,
 		data_ptr += page_length;
 	}
 
-out_unpin_pages:
-	for (i = 0; i < pinned_pages; i++)
+out:
+	for (i = 0; i < num_pages; i++)
 		page_cache_release(user_pages[i]);
 	drm_free_large(user_pages);
 
@@ -803,11 +832,11 @@ i915_gem_shmem_pwrite_fast(struct drm_device *dev,
 		if (IS_ERR(page))
 			return PTR_ERR(page);
 
-		vaddr = kmap_atomic(page, KM_USER0);
+		vaddr = kmap_atomic(page);
 		ret = __copy_from_user_inatomic(vaddr + page_offset,
 						user_data,
 						page_length);
-		kunmap_atomic(vaddr, KM_USER0);
+		kunmap_atomic(vaddr);
 
 		set_page_dirty(page);
 		mark_page_accessed(page);
@@ -842,11 +871,10 @@ i915_gem_shmem_pwrite_slow(struct drm_device *dev,
 			   struct drm_file *file)
 {
 	struct address_space *mapping = obj->base.filp->f_path.dentry->d_inode->i_mapping;
-	struct mm_struct *mm = current->mm;
 	struct page **user_pages;
 	ssize_t remain;
-	loff_t offset, pinned_pages, i;
-	loff_t first_data_page, last_data_page, num_pages;
+	loff_t first_data_page, last_data_page, offset;
+	int num_pages, i;
 	int shmem_page_offset;
 	int data_page_index,  data_page_offset;
 	int page_length;
@@ -864,20 +892,10 @@ i915_gem_shmem_pwrite_slow(struct drm_device *dev,
 	last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
 	num_pages = last_data_page - first_data_page + 1;
 
-	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, 0, 0, user_pages, NULL);
-	up_read(&mm->mmap_sem);
-	mutex_lock(&dev->struct_mutex);
-	if (pinned_pages < num_pages) {
-		ret = -EFAULT;
+	ret = i915_gem_get_user_pages(dev, data_ptr, false,
+				      &num_pages, &user_pages);
+	if (ret)
 		goto out;
-	}
 
 	ret = i915_gem_object_set_to_cpu_domain(obj, 1);
 	if (ret)
@@ -940,7 +958,7 @@ i915_gem_shmem_pwrite_slow(struct drm_device *dev,
 	}
 
 out:
-	for (i = 0; i < pinned_pages; i++)
+	for (i = 0; i < num_pages; i++)
 		page_cache_release(user_pages[i]);
 	drm_free_large(user_pages);
 
-- 
1.7.4.1