Re: [PATCH 06/34] drm/i915: convert put_page() to put_user_page*()

[John Hubbard]

On 8/2/19 2:19 AM, Joonas Lahtinen wrote:
> Quoting john.hubbard@xxxxxxxxx (2019-08-02 05:19:37)
> > From: John Hubbard <jhubbard@xxxxxxxxxx>
> >
> > For pages that were retained via get_user_pages*(), release those pages
> > via the new put_user_page*() routines, instead of via put_page() or
> > release_pages().
> >
> > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
> > ("mm: introduce put_user_page*(), placeholder versions").
> >
> > Note that this effectively changes the code's behavior in
> > i915_gem_userptr_put_pages(): it now calls set_page_dirty_lock(),
> > instead of set_page_dirty(). This is probably more accurate.
>
> We've already fixed this in drm-tip where the current code uses
> set_page_dirty_lock().
>
> This would conflict with our tree. Rodrigo is handling
> drm-intel-next for 5.4, so you guys want to coordinate how
> to merge.

Hi Joonas, Rodrigo,

First of all, I apologize for the API breakage: put_user_pages_dirty_lock()
has an additional "dirty" parameter.

In order to deal with the merge problem, I'll drop this patch from my series,
and I'd recommend that the drm-intel-next take the following approach:

1) For now, s/put_page/put_user_page/ in i915_gem_userptr_put_pages(),
and fix up the set_page_dirty() --> set_page_dirty_lock() issue, like this
(based against linux.git):

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c 
b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 528b61678334..94721cc0093b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -664,10 +664,10 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,

        for_each_sgt_page(page, sgt_iter, pages) {
                if (obj->mm.dirty)
-                       set_page_dirty(page);
+                       set_page_dirty_lock(page);

                mark_page_accessed(page);
-               put_page(page);
+               put_user_page(page);
        }
        obj->mm.dirty = false;


That will leave you with your original set_page_dirty_lock() calls
and everything works properly.

2) Next cycle, move to the new put_user_pages_dirty_lock().

thanks,
--
John Hubbard
NVIDIA


> Regards, Joonas