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 Re: [Xen-devel] [PATCH 06/34] drm/i915: convert put_page() to put_user_page*()
 
To: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, <john.hubbard@xxxxxxxxx>From: John Hubbard <jhubbard@xxxxxxxxxx>Date: Fri, 2 Aug 2019 11:48:08 -0700Cc: linux-fbdev@xxxxxxxxxxxxxxx, Jan Kara <jack@xxxxxxx>, kvm@xxxxxxxxxxxxxxx, David Airlie <airlied@xxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, dri-devel@xxxxxxxxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, Ira Weiny <ira.weiny@xxxxxxxxx>, ceph-devel@xxxxxxxxxxxxxxx, devel@xxxxxxxxxxxxxxxxxxxx, rds-devel@xxxxxxxxxxxxxx, linux-rdma@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, amd-gfx@xxxxxxxxxxxxxxxxxxxxx, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Jason Gunthorpe <jgg@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, devel@xxxxxxxxxxxxxxxxxx, linux-media@xxxxxxxxxxxxxxx, intel-gfx@xxxxxxxxxxxxxxxxxxxxx, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>, linux-block@xxxxxxxxxxxxxxx, Jérôme Glisse <jglisse@xxxxxxxxxx>, linux-rpi-kernel@xxxxxxxxxxxxxxxxxxx, Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>, Dan Williams <dan.j.williams@xxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-nfs@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>, linux-xfs@xxxxxxxxxxxxxxx, linux-crypto@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxxDelivery-date: Fri, 02 Aug 2019 18:49:57 +0000List-id: Xen developer discussion <xen-devel.lists.xenproject.org> 
 
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
 
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