linux-kernel - Re: [PATCH v2 06/11] mm/hmm: improve driver API to work and wait over a range v2

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Date:   Thu, 28 Mar 2019 11:49:06 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        John Hubbard <jhubbard@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v2 06/11] mm/hmm: improve driver API to work and wait
 over a range v2

On Thu, Mar 28, 2019 at 08:56:54PM -0400, Jerome Glisse wrote:
> On Thu, Mar 28, 2019 at 09:12:21AM -0700, Ira Weiny wrote:
> > On Mon, Mar 25, 2019 at 10:40:06AM -0400, Jerome Glisse wrote:
> > > From: Jérôme Glisse <jglisse@...hat.com>
> > > 

[snip]

> > > +/*
> > > + * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
> > > + *
> > > + * When waiting for mmu notifiers we need some kind of time out otherwise we
> > > + * could potentialy wait for ever, 1000ms ie 1s sounds like a long time to
> > > + * wait already.
> > > + */
> > > +#define HMM_RANGE_DEFAULT_TIMEOUT 1000
> > > +
> > >  /* This is a temporary helper to avoid merge conflict between trees. */
> > > +static inline bool hmm_vma_range_done(struct hmm_range *range)
> > > +{
> > > +	bool ret = hmm_range_valid(range);
> > > +
> > > +	hmm_range_unregister(range);
> > > +	return ret;
> > > +}
> > > +
> > >  static inline int hmm_vma_fault(struct hmm_range *range, bool block)
> > >  {
> > > -	long ret = hmm_range_fault(range, block);
> > > -	if (ret == -EBUSY)
> > > -		ret = -EAGAIN;
> > > -	else if (ret == -EAGAIN)
> > > -		ret = -EBUSY;
> > > -	return ret < 0 ? ret : 0;
> > > +	long ret;
> > > +
> > > +	ret = hmm_range_register(range, range->vma->vm_mm,
> > > +				 range->start, range->end);
> > > +	if (ret)
> > > +		return (int)ret;
> > > +
> > > +	if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
> > > +		up_read(&range->vma->vm_mm->mmap_sem);
> > > +		return -EAGAIN;
> > > +	}
> > > +
> > > +	ret = hmm_range_fault(range, block);
> > > +	if (ret <= 0) {
> > > +		if (ret == -EBUSY || !ret) {
> > > +			up_read(&range->vma->vm_mm->mmap_sem);
> > > +			ret = -EBUSY;
> > > +		} else if (ret == -EAGAIN)
> > > +			ret = -EBUSY;
> > > +		hmm_range_unregister(range);
> > > +		return ret;
> > > +	}
> > > +	return 0;
> > 
> > Is hmm_vma_fault() also temporary to keep the nouveau driver working?  It looks
> > like it to me.
> > 
> > This and hmm_vma_range_done() above are part of the old interface which is in
> > the Documentation correct?  As stated above we should probably change that
> > documentation with this patch to ensure no new users of these 2 functions
> > appear.
> 
> Ok will update the documentation, note that i already posted patches to use
> this new API see the ODP RDMA link in the cover letter.
> 

Thanks,  Sorry for my previous email on this patch.  After looking more I see
that this is the old interface but this was not clear.  And I have not had time
to follow the previous threads.  I'm finding time to do this now...

Sorry,
Ira