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

From: John Hubbard <jhubbard@nvidia.com>
To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	<john.hubbard@gmail.com>
Cc: "Christoph Hellwig" <hch@infradead.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Dave Chinner" <david@fromorbit.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	amd-gfx@lists.freedesktop.org, ceph-devel@vger.kernel.org,
	devel@driverdev.osuosl.org, devel@lists.orangefs.org,
	dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
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	linux-rpi-kernel@lists.infradead.org, linux-xfs@vger.kernel.org,
	netdev@vger.kernel.org, rds-devel@oss.oracle.com,
	sparclinux@vger.kernel.org, x86@kernel.org,
	xen-devel@lists.xenproject.org,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"David Airlie" <airlied@linux.ie>
Subject: Re: [PATCH 06/34] drm/i915: convert put_page() to put_user_page*()
Date: Fri, 2 Aug 2019 11:48:08 -0700	[thread overview]
Message-ID: <7d9a9c57-4322-270b-b636-7214019f87e9@nvidia.com> (raw)
In-Reply-To: <156473756254.19842.12384378926183716632@jlahtine-desk.ger.corp.intel.com>

On 8/2/19 2:19 AM, Joonas Lahtinen wrote:
> Quoting john.hubbard@gmail.com (2019-08-02 05:19:37)
>> From: John Hubbard <jhubbard@nvidia.com>
>>
>> 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
> 
