Re: [PATCH v3 hmm 06/12] mm/hmm: Hold on to the mmget for the lifetime of the range

From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>
Cc: Andrea Arcangeli
	<aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Philip Yang <Philip.Yang-5C7GfCeVMHo@public.gmane.org>,
	Ralph Campbell
	<rcampbell-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	John Hubbard <jhubbard-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Felix.Kuehling-5C7GfCeVMHo@public.gmane.org,
	dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	Jerome Glisse <jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	Ben Skeggs <bskeggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v3 hmm 06/12] mm/hmm: Hold on to the mmget for the lifetime of the range
Date: Sat, 15 Jun 2019 07:14:35 -0700	[thread overview]
Message-ID: <20190615141435.GF17724@infradead.org> (raw)
In-Reply-To: <20190614004450.20252-7-jgg-uk2M96/98Pc@public.gmane.org>

>  	mutex_lock(&hmm->lock);
> -	list_for_each_entry(range, &hmm->ranges, list)
> -		range->valid = false;
> -	wake_up_all(&hmm->wq);
> +	/*
> +	 * Since hmm_range_register() holds the mmget() lock hmm_release() is
> +	 * prevented as long as a range exists.
> +	 */
> +	WARN_ON(!list_empty(&hmm->ranges));
>  	mutex_unlock(&hmm->lock);

This can just use list_empty_careful and avoid the lock entirely.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
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