dma-buf: add reservation_object_copy_fences (v2)

Allows us to copy all the fences in a reservation object to another one.

v2: handle NULL src_list

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1502384509-10465-2-git-send-email-alexander.deucher@amd.com

2 files changed, 63 insertions, 0 deletions

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index 87f8f5747500..d4881f91c43b 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -262,6 +262,66 @@ void reservation_object_add_excl_fence(struct reservation_object *obj,
 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 
 /**
+* reservation_object_copy_fences - Copy all fences from src to dst.
+* @dst: the destination reservation object
+* @src: the source reservation object
+*
+* Copy all fences from src to dst. Both src->lock as well as dst-lock must be
+* held.
+*/
+int reservation_object_copy_fences(struct reservation_object *dst,
+                                   struct reservation_object *src)
+{
+        struct reservation_object_list *src_list, *dst_list;
+        struct dma_fence *old, *new;
+        size_t size;
+        unsigned i;
+
+        src_list = reservation_object_get_list(src);
+
+        if (src_list) {
+                size = offsetof(typeof(*src_list),
+                                shared[src_list->shared_count]);
+                dst_list = kmalloc(size, GFP_KERNEL);
+                if (!dst_list)
+                        return -ENOMEM;
+
+                dst_list->shared_count = src_list->shared_count;
+                dst_list->shared_max = src_list->shared_count;
+                for (i = 0; i < src_list->shared_count; ++i)
+                        dst_list->shared[i] =
+                                dma_fence_get(src_list->shared[i]);
+        } else {
+                dst_list = NULL;
+        }
+
+        kfree(dst->staged);
+        dst->staged = NULL;
+
+        src_list = reservation_object_get_list(dst);
+
+        old = reservation_object_get_excl(dst);
+        new = reservation_object_get_excl(src);
+
+        dma_fence_get(new);
+
+        preempt_disable();
+        write_seqcount_begin(&dst->seq);
+        /* write_seqcount_begin provides the necessary memory barrier */
+        RCU_INIT_POINTER(dst->fence_excl, new);
+        RCU_INIT_POINTER(dst->fence, dst_list);
+        write_seqcount_end(&dst->seq);
+        preempt_enable();
+
+        if (src_list)
+                kfree_rcu(src_list, rcu);
+        dma_fence_put(old);
+
+        return 0;
+}
+EXPORT_SYMBOL(reservation_object_copy_fences);
+
+/**
  * reservation_object_get_fences_rcu - Get an object's shared and exclusive
  * fences without update side lock held
  * @obj: the reservation object
diff --git a/include/linux/reservation.h b/include/linux/reservation.h
index 156cfd330b66..21fc84d82d41 100644
--- a/include/linux/reservation.h
+++ b/include/linux/reservation.h
@@ -254,6 +254,9 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
                                       unsigned *pshared_count,
                                       struct dma_fence ***pshared);
 
+int reservation_object_copy_fences(struct reservation_object *dst,
+                                   struct reservation_object *src);
+
 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
                                          bool wait_all, bool intr,
                                          unsigned long timeout);