dma-buf: Expand reservation_list to fill allocation

Since kmalloc() will round up the allocation to the next slab size or
page, it will normally return a pointer to a memory block bigger than we
asked for. We can query for the actual size of the allocated block using
ksize() and expand our variable size reservation_list to take advantage
of that extra space.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Christian König <christian.koenig@amd.com>
Cc: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712080314.21018-1-chris@chris-wilson.co.uk

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index a6ac2b3a0185aafd09068b2622a63ab6b17fd2db..80ecc1283d155dcd071ac3fb63be9d7c273a7d27 100644 (file)
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -153,7 +153,9 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
                        RCU_INIT_POINTER(new->shared[j++], fence);
        }
        new->shared_count = j;
-       new->shared_max = max;
+       new->shared_max =
+               (ksize(new) - offsetof(typeof(*new), shared)) /
+               sizeof(*new->shared);
 
        preempt_disable();
        write_seqcount_begin(&obj->seq);
@@ -169,7 +171,7 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
                return 0;
 
        /* Drop the references to the signaled fences */
-       for (i = k; i < new->shared_max; ++i) {
+       for (i = k; i < max; ++i) {
                struct dma_fence *fence;
 
                fence = rcu_dereference_protected(new->shared[i],