[PATCH 03/17] drm/i915: Pin pages whilst mapping the dma-buf

Rodrigo Vivi
2013-08-26T22:51:25Z

From: Chris Wilson <chris@chris-wilson.co.uk>

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>
---
drivers/gpu/drm/i915/i915_gem_dmabuf.c | 41 ++++++++++++++++++----------------
1 file 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 e918b05..7d5752f 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,
--
1.8.1.4