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>

1 files changed, 43 insertions, 56 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1177ff577914..efc6a4e3b1d2 100644
--- 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)
+        if (ret == -EFAULT)