Re: [PATCH v3 9/9] dma-buf: Remove internal lock

[Christian König]

Am 24.08.22 um 12:22 schrieb Dmitry Osipenko:

The internal dma-buf lock isn't needed anymore because the updated
locking specification claims that dma-buf reservation must be locked
by importers, and thus, the internal data is already protected by the
reservation lock. Remove the obsoleted internal lock.

Signed-off-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>

Reviewed-by: Christian König <christian.koe...@amd.com>

---
  drivers/dma-buf/dma-buf.c | 14 ++++----------
  include/linux/dma-buf.h   |  9 ---------
  2 files changed, 4 insertions(+), 19 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 696d132b02f4..a0406254f0ae 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -656,7 +656,6 @@ struct dma_buf *dma_buf_export(const struct 
dma_buf_export_info *exp_info)

dmabuf->file = file; - mutex_init(&dmabuf->lock);

        INIT_LIST_HEAD(&dmabuf->attachments);

mutex_lock(&db_list.lock);

@@ -1503,7 +1502,7 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_mmap_unlocked, DMA_BUF);
  int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
  {
        struct iosys_map ptr;
-       int ret = 0;
+       int ret;

iosys_map_clear(map); @@ -1515,28 +1514,25 @@ int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)

        if (!dmabuf->ops->vmap)
                return -EINVAL;

- mutex_lock(&dmabuf->lock);

        if (dmabuf->vmapping_counter) {
                dmabuf->vmapping_counter++;
                BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
                *map = dmabuf->vmap_ptr;
-               goto out_unlock;
+               return 0;
        }

BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr)); ret = dmabuf->ops->vmap(dmabuf, &ptr);

        if (WARN_ON_ONCE(ret))
-               goto out_unlock;
+               return ret;

dmabuf->vmap_ptr = ptr;

        dmabuf->vmapping_counter = 1;

*map = dmabuf->vmap_ptr; -out_unlock:

-       mutex_unlock(&dmabuf->lock);
-       return ret;
+       return 0;
  }
  EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);

@@ -1578,13 +1574,11 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)

        BUG_ON(dmabuf->vmapping_counter == 0);
        BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));

- mutex_lock(&dmabuf->lock);

        if (--dmabuf->vmapping_counter == 0) {
                if (dmabuf->ops->vunmap)
                        dmabuf->ops->vunmap(dmabuf, map);
                iosys_map_clear(&dmabuf->vmap_ptr);
        }
-       mutex_unlock(&dmabuf->lock);
  }
  EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h

index d48d534dc55c..aed6695bbb50 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -326,15 +326,6 @@ struct dma_buf {
        /** @ops: dma_buf_ops associated with this buffer object. */
        const struct dma_buf_ops *ops;

- /**

-        * @lock:
-        *
-        * Used internally to serialize list manipulation, attach/detach and
-        * vmap/unmap. Note that in many cases this is superseeded by
-        * dma_resv_lock() on @resv.
-        */
-       struct mutex lock;
-
        /**
         * @vmapping_counter:
         *