[PATCH] dma-buf: add attachments empty check for dma_buf_release

[guangming.cao]

From: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>

Since there is no mandatory inspection for attachments in dma_buf_release.
There will be a case that dma_buf already released but attachment is still
in use, which can points to the dmabuf, and it maybe cause
some unexpected issues.

With IOMMU, when this cases occurs, there will have IOMMU address
translation fault(s) followed by this warning,
I think it's useful for dma devices to debug issue.

Signed-off-by: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>
---
 drivers/dma-buf/dma-buf.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 511fe0d217a0..672404857d6a 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -74,6 +74,29 @@ static void dma_buf_release(struct dentry *dentry)
 	 */
 	BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
 
+	/* attachment check */
+	if (dma_resv_trylock(dmabuf->resv) && WARN(!list_empty(&dmabuf->attachments),
+	    "%s err, inode:%08lu size:%08zu name:%s exp_name:%s flags:0x%08x mode:0x%08x, %s\n",
+	    __func__, file_inode(dmabuf->file)->i_ino, dmabuf->size,
+	    dmabuf->name, dmabuf->exp_name,
+	    dmabuf->file->f_flags, dmabuf->file->f_mode,
+	    "Release dmabuf before detach all attachments, dump attach:\n")) {
+		int attach_cnt = 0;
+		dma_addr_t dma_addr;
+		struct dma_buf_attachment *attach_obj;
+		/* dump all attachment info */
+		list_for_each_entry(attach_obj, &dmabuf->attachments, node) {
+			dma_addr = (dma_addr_t)0;
+			if (attach_obj->sgt)
+				dma_addr = sg_dma_address(attach_obj->sgt->sgl);
+			pr_err("attach[%d]: dev:%s dma_addr:0x%-12lx\n",
+			       attach_cnt, dev_name(attach_obj->dev), dma_addr);
+			attach_cnt++;
+		}
+		pr_err("Total %d devices attached\n\n", attach_cnt);
+		dma_resv_unlock(dmabuf->resv);
+	}
+
 	dmabuf->ops->release(dmabuf);
 
 	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
-- 
2.17.1