Add a comment why there is a obj refcount inc before installing
the vm_ops for the mmap call. Also remove the invalid older comment
as drm API(drm_gem_prime_mmap()) will hold an obj reference before
calling this driver mmap callback so we can't have 0-refcnted
object here.
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index d3c1dee16af2..0bc8c3818443 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -952,9 +952,10 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
vma_pages(vma));
if (node && drm_vma_node_is_allowed(node, priv)) {
/*
- * Skip 0-refcnted objects as it is in the process of being
- * destroyed and will be invalid when the vma manager lock
- * is released.
+ * When we install vm_ops for mmap we are too late for
+ * the vm_ops->open() which increases the ref_count of
+ * this obj and then it gets decreased by the vm_ops->close().
+ * To balance this increase the obj ref_count here.
*/
if (!node->driver_private) {
mmo = container_of(node, struct i915_mmap_offset, vma_node);
--
2.39.0
