drm/i915: Truncate the shmem backing pages on purge

shmfs doesn't actually implement i_ops->truncate() so we were not
immedatiately releasing the backing pages when shrinking the gfx cache
under OOM. Instead use a combination of truncate_inode_pages() and
i_ops->truncate_range() as is used by shmem_delete_inode().

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 8f3e0c10c08003a7422895835eb9fbcf1beaaac4..41306217bd7ad28b0ec95c07a3cb3f6d58b25c57 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1505,9 +1505,16 @@ i915_gem_object_truncate(struct drm_gem_object *obj)
        struct drm_i915_gem_object *obj_priv = to_intel_bo(obj);
        struct inode *inode;
 
+       /* Our goal here is to return as much of the memory as
+        * is possible back to the system as we are called from OOM.
+        * To do this we must instruct the shmfs to drop all of its
+        * backing pages, *now*. Here we mirror the actions taken
+        * when by shmem_delete_inode() to release the backing store.
+        */
        inode = obj->filp->f_path.dentry->d_inode;
-       if (inode->i_op->truncate)
-               inode->i_op->truncate (inode);
+       truncate_inode_pages(inode->i_mapping, 0);
+       if (inode->i_op->truncate_range)
+               inode->i_op->truncate_range(inode, 0, (loff_t)-1);
 
        obj_priv->madv = __I915_MADV_PURGED;
 }