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>

diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index e918b05fcbdd16e238457f7e286b345bdf651731..7d5752fda5f18b7850beeed588a6f1b3a85cd79a 100644 (file)
--- 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,