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Message-ID: <bd2308d6-38e5-6042-3da8-fb436f67a88e@collabora.com>
Date:   Mon, 20 Nov 2023 14:02:29 +0300
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Subject: Re: [PATCH v18 11/26] drm/shmem-helper: Prepare drm_gem_shmem_free()
 to shrinker addition
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To:     Boris Brezillon <boris.brezillon@collabora.com>
Cc:     David Airlie <airlied@gmail.com>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        Qiang Yu <yuq825@gmail.com>,
        Steven Price <steven.price@arm.com>,
        Emma Anholt <emma@anholt.net>, Melissa Wen <mwen@igalia.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        kernel@collabora.com, virtualization@lists.linux-foundation.org
References: <20231029230205.93277-1-dmitry.osipenko@collabora.com>
 <20231029230205.93277-12-dmitry.osipenko@collabora.com>
 <20231110111601.5d6bd1ab@collabora.com>
From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
In-Reply-To: <20231110111601.5d6bd1ab@collabora.com>
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Precedence: bulk

On 11/10/23 13:16, Boris Brezillon wrote:
> On Mon, 30 Oct 2023 02:01:50 +0300
> Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:
> 
>> Prepare drm_gem_shmem_free() to addition of memory shrinker support
>> to drm-shmem by adding and using variant of put_pages() that doesn't
>> touch reservation lock. Reservation shouldn't be touched because lockdep
>> will trigger a bogus warning about locking contention with fs_reclaim
>> code paths that can't happen during the time when GEM is freed and
>> lockdep doesn't know about that.
>>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>> ---
>>  drivers/gpu/drm/drm_gem_shmem_helper.c | 35 +++++++++++++-------------
>>  1 file changed, 18 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index 08b5a57c59d8..24ff2b99e75b 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -128,6 +128,22 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
>>  }
>>  EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
>>  
>> +static void
>> +drm_gem_shmem_free_pages(struct drm_gem_shmem_object *shmem)
>> +{
>> +	struct drm_gem_object *obj = &shmem->base;
>> +
>> +#ifdef CONFIG_X86
>> +	if (shmem->map_wc)
>> +		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
>> +#endif
>> +
>> +	drm_gem_put_pages(obj, shmem->pages,
>> +			  shmem->pages_mark_dirty_on_put,
>> +			  shmem->pages_mark_accessed_on_put);
>> +	shmem->pages = NULL;
>> +}
>> +
>>  /**
>>   * drm_gem_shmem_free - Free resources associated with a shmem GEM object
>>   * @shmem: shmem GEM object to free
>> @@ -142,8 +158,6 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>>  	if (obj->import_attach) {
>>  		drm_prime_gem_destroy(obj, shmem->sgt);
>>  	} else {
>> -		dma_resv_lock(shmem->base.resv, NULL);
>> -
>>  		drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));
>>  
>>  		if (shmem->sgt) {
>> @@ -157,8 +171,6 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>>  
> If you drop the dma_resv_lock/unlock(), you should also replace the
> drm_gem_shmem_put_pages_locked() by a drm_gem_shmem_free_pages() in this
> commit.

drm_gem_shmem_put_pages_locked() is exported by a later patch of this
series, it's not worthwhile to remove this function

-- 
Best regards,
Dmitry