drm/i915: Remove walk over obj->vma_list for the shrinker

In the next patch, we want to reduce the lock coverage within the
shrinker, and one of the dangerous walks we have is over obj->vma_list.
We are only walking the obj->vma_list in order to check whether it has
been permanently pinned by HW access, typically via use on the scanout.
But we have a couple of other long term pins, the context objects for
which we currently have to check the individual vma pin_count. If we
instead mark these using obj->pin_display, we can forgo the dangerous
and sometimes slow list iteration.

v2: Rearrange code to try and avoid confusion from false associations
due to arrangement of whitespace along with rebasing on obj->pin_global.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013202621.7276-4-chris@chris-wilson.co.uk

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index b2a6cb09c6e7..8da1bde442dd 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1244,6 +1244,8 @@ int intel_ring_pin(struct intel_ring *ring,
         if (IS_ERR(addr))
                 goto err;
 
+        vma->obj->pin_global++;
+
         ring->vaddr = addr;
         return 0;
 
@@ -1275,6 +1277,7 @@ void intel_ring_unpin(struct intel_ring *ring)
                 i915_gem_object_unpin_map(ring->vma->obj);
         ring->vaddr = NULL;
 
+        ring->vma->obj->pin_global--;
         i915_vma_unpin(ring->vma);
 }
 
@@ -1439,6 +1442,7 @@ intel_ring_context_pin(struct intel_engine_cs *engine,
                         goto err;
 
                 ce->state->obj->mm.dirty = true;
+                ce->state->obj->pin_global++;
         }
 
         /* The kernel context is only used as a placeholder for flushing the
@@ -1473,8 +1477,10 @@ static void intel_ring_context_unpin(struct intel_engine_cs *engine,
         if (--ce->pin_count)
                 return;
 
-        if (ce->state)
+        if (ce->state) {
+                ce->state->obj->pin_global--;
                 i915_vma_unpin(ce->state);
+        }
 
         i915_gem_context_put(ctx);
 }