[PATCH v4 16/21] dma-buf: Move dma_buf_attach() to dynamic locking specification

[Dmitry Osipenko]

Move dma-buf attachment API functions to the dynamic locking specification
by taking the reservation lock around the mapping operations. The strict
locking convention prevents deadlock situations for dma-buf importers and
exporters.

Signed-off-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
---
 drivers/dma-buf/dma-buf.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index ceea4839c641..073942bf5ae9 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -858,8 +858,8 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct 
device *dev,
            dma_buf_is_dynamic(dmabuf)) {
                struct sg_table *sgt;
 
+               dma_resv_lock(attach->dmabuf->resv, NULL);
                if (dma_buf_is_dynamic(attach->dmabuf)) {
-                       dma_resv_lock(attach->dmabuf->resv, NULL);
                        ret = dmabuf->ops->pin(attach);
                        if (ret)
                                goto err_unlock;
@@ -872,8 +872,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct 
device *dev,
                        ret = PTR_ERR(sgt);
                        goto err_unpin;
                }
-               if (dma_buf_is_dynamic(attach->dmabuf))
-                       dma_resv_unlock(attach->dmabuf->resv);
+               dma_resv_unlock(attach->dmabuf->resv);
                attach->sgt = sgt;
                attach->dir = DMA_BIDIRECTIONAL;
        }
@@ -889,8 +888,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct 
device *dev,
                dmabuf->ops->unpin(attach);
 
 err_unlock:
-       if (dma_buf_is_dynamic(attach->dmabuf))
-               dma_resv_unlock(attach->dmabuf->resv);
+       dma_resv_unlock(attach->dmabuf->resv);
 
        dma_buf_detach(dmabuf, attach);
        return ERR_PTR(ret);
@@ -936,21 +934,19 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct 
dma_buf_attachment *attach)
        if (WARN_ON(!dmabuf || !attach))
                return;
 
+       dma_resv_lock(attach->dmabuf->resv, NULL);
+
        if (attach->sgt) {
-               if (dma_buf_is_dynamic(attach->dmabuf))
-                       dma_resv_lock(attach->dmabuf->resv, NULL);
 
                __unmap_dma_buf(attach, attach->sgt, attach->dir);
 
-               if (dma_buf_is_dynamic(attach->dmabuf)) {
+               if (dma_buf_is_dynamic(attach->dmabuf))
                        dmabuf->ops->unpin(attach);
-                       dma_resv_unlock(attach->dmabuf->resv);
-               }
        }
-
-       dma_resv_lock(dmabuf->resv, NULL);
        list_del(&attach->node);
+
        dma_resv_unlock(dmabuf->resv);
+
        if (dmabuf->ops->detach)
                dmabuf->ops->detach(dmabuf, attach);
 
-- 
2.37.2