drm/i915: Clear execbuf's vma backpointer upon release

commit 2889caa92321 ("drm/i915: Eliminate lots of iterations over the
execobjects array") jiggled around the error handling and replace a test
that we cleaned up properly after ourselves with an assertion. That
assertion failed because in the release function (moments after the
assertion) we were indeed forgetting to mark the vma as cleared. The
consequence was when testing an invalid relocation address, we would try
to release the vma twice (following the couple of attempts to verify the
address) and on the second release notice that the first release was
incomplete.

Testcase: igt/gem_reloc_overflow/invalid-address
Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170622104722.2583-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index b2457556591c0b64057805e8043a345621900e66..ec33b358fba9503b5435fb3a7df9cc0734a13b39 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -879,6 +879,7 @@ static void eb_release_vmas(const struct i915_execbuffer *eb)
 
                GEM_BUG_ON(vma->exec_entry != entry);
                vma->exec_entry = NULL;
+               __exec_to_vma(entry) = 0;
 
                if (entry->flags & __EXEC_OBJECT_HAS_PIN)
                        __eb_unreserve_vma(vma, entry);