drm/i915: Pin pages whilst mapping the dma-buf

As we attempt to kmalloc after calling get_pages, there is a possibility
that the shrinker may reap the pages we just acquired. To prevent this
we need to increment the pages_pin_count early, so rearrange the code
and error paths to make it so.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 22 insertions, 19 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index e918b05fcbdd..7d5752fda5f1 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -42,27 +42,24 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attachme
 
         ret = i915_mutex_lock_interruptible(obj->base.dev);
         if (ret)
-                return ERR_PTR(ret);
+                goto err;
 
         ret = i915_gem_object_get_pages(obj);
-        if (ret) {
-                st = ERR_PTR(ret);
-                goto out;
-        }
+        if (ret)
+                goto err_unlock;
+
+        i915_gem_object_pin_pages(obj);
 
         /* Copy sg so that we make an independent mapping */
         st = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
         if (st == NULL) {
-                st = ERR_PTR(-ENOMEM);
-                goto out;
+                ret = -ENOMEM;
+                goto err_unpin;
         }
 
         ret = sg_alloc_table(st, obj->pages->nents, GFP_KERNEL);
-        if (ret) {
-                kfree(st);
-                st = ERR_PTR(ret);
-                goto out;
-        }
+        if (ret)
+                goto err_free;
 
         src = obj->pages->sgl;
         dst = st->sgl;
@@ -73,17 +70,23 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attachme
         }
 
         if (!dma_map_sg(attachment->dev, st->sgl, st->nents, dir)) {
-                sg_free_table(st);
-                kfree(st);
-                st = ERR_PTR(-ENOMEM);
-                goto out;
+                ret =-ENOMEM;
+                goto err_free_sg;
         }
 
-        i915_gem_object_pin_pages(obj);
-
-out:
         mutex_unlock(&obj->base.dev->struct_mutex);
         return st;
+
+err_free_sg:
+        sg_free_table(st);
+err_free:
+        kfree(st);
+err_unpin:
+        i915_gem_object_unpin_pages(obj);
+err_unlock:
+        mutex_unlock(&obj->base.dev->struct_mutex);
+err:
+        return ERR_PTR(ret);
 }
 
 static void i915_gem_unmap_dma_buf(struct dma_buf_attachment *attachment,