[Xen-devel] [PATCH 07/11] ttm: Do not set the ttm->be to NULL before calling the TTM page pool to free pages.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

. as the ttm->be->func->[get|put]_pages can be called and they would
dereference on ttm->be which was set to NULL.

Instead of clearing it there, pass in a flag to the ttm_tt_free_allocated_pages
whether to clear the pages or not (you are not suppose to clear the pages
when destroying them).

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/gpu/drm/ttm/ttm_tt.c |   15 +++++++--------
 1 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index 76c982f..31ae359 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -276,7 +276,7 @@ int ttm_tt_set_placement_caching(struct ttm_tt *ttm, 
uint32_t placement)
 }
 EXPORT_SYMBOL(ttm_tt_set_placement_caching);
 
-static void ttm_tt_free_alloced_pages(struct ttm_tt *ttm)
+static void ttm_tt_free_alloced_pages(struct ttm_tt *ttm, bool call_clear)
 {
        int i;
        unsigned count = 0;
@@ -286,7 +286,7 @@ static void ttm_tt_free_alloced_pages(struct ttm_tt *ttm)
 
        INIT_LIST_HEAD(&h);
 
-       if (be)
+       if (be && call_clear)
                be->func->clear(be);
        for (i = 0; i < ttm->num_pages; ++i) {
 
@@ -317,16 +317,14 @@ void ttm_tt_destroy(struct ttm_tt *ttm)
                return;
 
        be = ttm->be;
-       if (likely(be != NULL)) {
+       if (likely(be != NULL))
                be->func->destroy(be);
-               ttm->be = NULL;
-       }
 
        if (likely(ttm->pages != NULL)) {
                if (ttm->page_flags & TTM_PAGE_FLAG_USER)
                        ttm_tt_free_user_pages(ttm);
                else
-                       ttm_tt_free_alloced_pages(ttm);
+                       ttm_tt_free_alloced_pages(ttm, false);
 
                ttm_tt_free_page_directory(ttm);
        }
@@ -335,6 +333,7 @@ void ttm_tt_destroy(struct ttm_tt *ttm)
            ttm->swap_storage)
                fput(ttm->swap_storage);
 
+       ttm->be = NULL;
        kfree(ttm);
 }
 
@@ -509,7 +508,7 @@ static int ttm_tt_swapin(struct ttm_tt *ttm)
 
        return 0;
 out_err:
-       ttm_tt_free_alloced_pages(ttm);
+       ttm_tt_free_alloced_pages(ttm, true);
        return ret;
 }
 
@@ -573,7 +572,7 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file 
*persistent_swap_storage)
                page_cache_release(to_page);
        }
 
-       ttm_tt_free_alloced_pages(ttm);
+       ttm_tt_free_alloced_pages(ttm, true);
        ttm->swap_storage = swap_storage;
        ttm->page_flags |= TTM_PAGE_FLAG_SWAPPED;
        if (persistent_swap_storage)
-- 
1.7.6.4


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