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Re: [Xen-devel] [PATCH v2 09/15] xen/gntdev: use mmu_range_notifier_insert
- To: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
- Date: Tue, 5 Nov 2019 02:31:12 +0000
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- Cc: Juergen Gross <jgross@xxxxxxxx>, David Zhou <David1.Zhou@xxxxxxx>, Ralph Campbell <rcampbell@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>, "linux-rdma@xxxxxxxxxxxxxxx" <linux-rdma@xxxxxxxxxxxxxxx>, John Hubbard <jhubbard@xxxxxxxxxx>, "Felix.Kuehling@xxxxxxx" <Felix.Kuehling@xxxxxxx>, Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>, "dri-devel@xxxxxxxxxxxxxxxxxxxxx" <dri-devel@xxxxxxxxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>, Jerome Glisse <jglisse@xxxxxxxxxx>, "amd-gfx@xxxxxxxxxxxxxxxxxxxxx" <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>, "nouveau@xxxxxxxxxxxxxxxxxxxxx" <nouveau@xxxxxxxxxxxxxxxxxxxxx>, Alex Deucher <alexander.deucher@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>, Petr Cvek <petrcvekcz@xxxxxxxxx>, Christian König <christian.koenig@xxxxxxx>, Ben Skeggs <bskeggs@xxxxxxxxxx>
- Delivery-date: Tue, 05 Nov 2019 02:31:33 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHVjcvKV253DVP8r0WB5NYgPgZcBad7m8uAgABKxgA=
- Thread-topic: [PATCH v2 09/15] xen/gntdev: use mmu_range_notifier_insert
On Mon, Nov 04, 2019 at 05:03:31PM -0500, Boris Ostrovsky wrote:
> On 10/28/19 4:10 PM, Jason Gunthorpe wrote:
> > @@ -445,17 +438,9 @@ static void gntdev_vma_close(struct vm_area_struct
> > *vma)
> > struct gntdev_priv *priv = file->private_data;
> >
> > pr_debug("gntdev_vma_close %p\n", vma);
> > - if (use_ptemod) {
> > - /* It is possible that an mmu notifier could be running
> > - * concurrently, so take priv->lock to ensure that the vma won't
> > - * vanishing during the unmap_grant_pages call, since we will
> > - * spin here until that completes. Such a concurrent call will
> > - * not do any unmapping, since that has been done prior to
> > - * closing the vma, but it may still iterate the unmap_ops list.
> > - */
> > - mutex_lock(&priv->lock);
> > + if (use_ptemod && map->vma == vma) {
>
>
> Is it possible for map->vma not to be equal to vma?
It could be NULL at least if use_ptemod is not set.
Otherwise, I'm not sure, the confusing bit is that the map comes from
here:
map = gntdev_find_map_index(priv, index, count);
It looks like the intent is that the map->vma is always set to the
only vma that has the map as private_data.
So, I suppose it can be relaxed to a null test and a WARN_ON that it
hasn't changed?
Jason
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