linux-kernel - [PATCH] drm/ttm: don't set page->mapping

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Date:   Fri, 20 Nov 2020 10:54:45 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        linux-mm@...ck.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Brian Paul <brianp@...are.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>
Subject: [PATCH] drm/ttm: don't set page->mapping

Random observation while trying to review Christian's patch series to
stop looking at struct page for dma-buf imports.

This was originally added in

commit 58aa6622d32af7d2c08d45085f44c54554a16ed7
Author: Thomas Hellstrom <thellstrom@...are.com>
Date:   Fri Jan 3 11:47:23 2014 +0100

    drm/ttm: Correctly set page mapping and -index members

    Needed for some vm operations; most notably unmap_mapping_range() with
    even_cows = 0.

    Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
    Reviewed-by: Brian Paul <brianp@...are.com>

but we do not have a single caller of unmap_mapping_range with
even_cows == 0. And all the gem drivers don't do this, so another
small thing we could standardize between drm and ttm drivers.

Plus I don't really see a need for unamp_mapping_range where we don't
want to indiscriminately shoot down all ptes.

Cc: Thomas Hellstrom <thellstrom@...are.com>
Cc: Brian Paul <brianp@...are.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Cc: Christian Koenig <christian.koenig@....com>
Cc: Huang Rui <ray.huang@....com>
---
 drivers/gpu/drm/ttm/ttm_tt.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index da9eeffe0c6d..5b2eb6d58bb7 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -284,17 +284,6 @@ int ttm_tt_swapout(struct ttm_bo_device *bdev, struct ttm_tt *ttm)
 	return ret;
 }
 
-static void ttm_tt_add_mapping(struct ttm_bo_device *bdev, struct ttm_tt *ttm)
-{
-	pgoff_t i;
-
-	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
-		return;
-
-	for (i = 0; i < ttm->num_pages; ++i)
-		ttm->pages[i]->mapping = bdev->dev_mapping;
-}
-
 int ttm_tt_populate(struct ttm_bo_device *bdev,
 		    struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
 {
@@ -313,7 +302,6 @@ int ttm_tt_populate(struct ttm_bo_device *bdev,
 	if (ret)
 		return ret;
 
-	ttm_tt_add_mapping(bdev, ttm);
 	ttm->page_flags |= TTM_PAGE_FLAG_PRIV_POPULATED;
 	if (unlikely(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
 		ret = ttm_tt_swapin(ttm);
-- 
2.29.2