[PATCH] Revert "drm/i915/userptr: Acquire the page lock around set_page_dirty()"

[Chris Wilson]

The userptr put_pages can be called from inside try_to_unmap, and so
enters with the page lock held on one of the object's backing pages. We
cannot take the page lock ourselves for fear of recursion.

Reported-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Reported-by: Martin Wilck <Martin.Wilck@xxxxxxxx>
Reported-by: Leo Kraav <leho@xxxxxxxxx>
Fixes: aa56a292ce62 ("drm/i915/userptr: Acquire the page lock around set_page_dirty()")
References: https://bugzilla.kernel.org/show_bug.cgi?id=203317
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 74da35611d7c..11b231c187c5 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -672,15 +672,7 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
 
 	for_each_sgt_page(page, sgt_iter, pages) {
 		if (obj->mm.dirty)
-			/*
-			 * As this may not be anonymous memory (e.g. shmem)
-			 * but exist on a real mapping, we have to lock
-			 * the page in order to dirty it -- holding
-			 * the page reference is not sufficient to
-			 * prevent the inode from being truncated.
-			 * Play safe and take the lock.
-			 */
-			set_page_dirty_lock(page);
+			set_page_dirty(page);
 
 		mark_page_accessed(page);
 		put_page(page);
-- 
2.23.0