[Intel-gfx] [PATCH] drm/i915: Do not invalidate obj->pages under mempressure

[Chris Wilson]

This (partially) reverts

commit 5537252b6b6d71fb1a8ed7395a8e5babf91953fd
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Mar 25 13:23:06 2014 +0000

    drm/i915: Invalidate our pages under memory pressure

It appears given the right workload, that pages which are swapped out
more than once are incorrectly invalidated and discarded. I had presumed
that the swapin would mark the pages dirty again and so preserve them
against the next cycle of invalidation - that appears to be false, and
leads to memory corruption (even leak of stale pages to userspace).

Reported-by: Sean V Kelley <sean.v.kelley at intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Sean V Kelley <sean.v.kelley at intel.com>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/i915/i915_gem.c | 23 ++---------------------
 1 file changed, 2 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4d453490596e..b06f051a73de 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1947,26 +1947,6 @@ i915_gem_object_truncate(struct drm_i915_gem_object *obj)
 	obj->madv = __I915_MADV_PURGED;
 }
 
-/* Try to discard unwanted pages */
-static void
-i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
-{
-	struct address_space *mapping;
-
-	switch (obj->madv) {
-	case I915_MADV_DONTNEED:
-		i915_gem_object_truncate(obj);
-	case __I915_MADV_PURGED:
-		return;
-	}
-
-	if (obj->base.filp == NULL)
-		return;
-
-	mapping = file_inode(obj->base.filp)->i_mapping,
-	invalidate_mapping_pages(mapping, 0, (loff_t)-1);
-}
-
 static void
 i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj)
 {
@@ -2029,7 +2009,8 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
 	ops->put_pages(obj);
 	obj->pages = NULL;
 
-	i915_gem_object_invalidate(obj);
+	if (i915_gem_object_is_purgeable(obj))
+		i915_gem_object_truncate(obj);
 
 	return 0;
 }
-- 
2.1.4