[PATCH v3 hmm 11/12] mm/hmm: Remove confusing comment and logic from hmm_release

[Jason Gunthorpe]

On Sat, Jun 15, 2019 at 07:21:06AM -0700, Christoph Hellwig wrote:
> On Thu, Jun 13, 2019 at 09:44:49PM -0300, Jason Gunthorpe wrote:
> > From: Jason Gunthorpe <jgg at mellanox.com>
> > 
> > hmm_release() is called exactly once per hmm. ops->release() cannot
> > accidentally trigger any action that would recurse back onto
> > hmm->mirrors_sem.
> 
> In linux-next amdgpu actually calls hmm_mirror_unregister from its
> release function.  That whole release function looks rather sketchy,
> but we probably need to sort that out first.

Does it? I see this:

static void amdgpu_hmm_mirror_release(struct hmm_mirror *mirror)
{
        struct amdgpu_mn *amn = container_of(mirror, struct amdgpu_mn, mirror);

        INIT_WORK(&amn->work, amdgpu_mn_destroy);
        schedule_work(&amn->work);
}

static struct hmm_mirror_ops amdgpu_hmm_mirror_ops[] = {
        [AMDGPU_MN_TYPE_GFX] = {
                .sync_cpu_device_pagetables = amdgpu_mn_sync_pagetables_gfx,
                .release = amdgpu_hmm_mirror_release
        },
        [AMDGPU_MN_TYPE_HSA] = {
                .sync_cpu_device_pagetables = amdgpu_mn_sync_pagetables_hsa,
                .release = amdgpu_hmm_mirror_release
        },
};


Am I looking at the wrong thing? Looks like it calls it through a work
queue should should be OK..

Though very strange that amdgpu only destroys the mirror via release,
that cannot be right.

Jason