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

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 <[email protected]>
Reported-by: Martin Wilck <[email protected]>
Reported-by: Leo Kraav <[email protected]>
Fixes: aa56a29 ("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 <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: [email protected]
Signed-off-by: Linus Torvalds <[email protected]>

drivers/gpu/drm/i915/gem/i915_gem_userptr.c

@@ -664,15 +664,7 @@ 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);