Re: [PATCH 01/13] drm/exynos: Stop using frame_vector helpers

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On 10/7/20 2:32 PM, Daniel Vetter wrote:
On Wed, Oct 7, 2020 at 10:33 PM John Hubbard <jhubbard@xxxxxxxxxx> wrote:

On 10/7/20 9:44 AM, Daniel Vetter wrote:
...
@@ -398,15 +399,11 @@ static void g2d_userptr_put_dma_addr(struct g2d_data *g2d,
       dma_unmap_sgtable(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt,
                         DMA_BIDIRECTIONAL, 0);

-     pages = frame_vector_pages(g2d_userptr->vec);
-     if (!IS_ERR(pages)) {
-             int i;
+     for (i = 0; i < g2d_userptr->npages; i++)
+             set_page_dirty_lock(g2d_userptr->pages[i]);

-             for (i = 0; i < frame_vector_count(g2d_userptr->vec); i++)
-                     set_page_dirty_lock(pages[i]);
-     }
-     put_vaddr_frames(g2d_userptr->vec);
-     frame_vector_destroy(g2d_userptr->vec);
+     unpin_user_pages(g2d_userptr->pages, g2d_userptr->npages);
+     kvfree(g2d_userptr->pages);

You can avoid writing your own loop, and just simplify the whole thing down to
two lines:

         unpin_user_pages_dirty_lock(g2d_userptr->pages, g2d_userptr->npages,
                                     true);
         kvfree(g2d_userptr->pages);

Oh nice, this is neat. I'll also roll it out in the habanalabs patch,
that has the same thing. Well almost, it only uses set_page_dirty, not
the _lock variant. But I have no idea whether that matters or not?


It matters. And invariably, call sites that use set_page_dirty() instead
of set_page_dirty_lock() were already wrong.  Which is why I never had to
provide anything like "unpin_user_pages_dirty (not locked)".

Although in habanalabs case, I just reviewed patch 3 and I think they *were*
correctly using set_page_dirty_lock()...

thanks,
--
John Hubbard
NVIDIA



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