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From: Yongji Xie <xieyongji@bytedance.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	sgarzare@redhat.com, Parav Pandit <parav@nvidia.com>,
	akpm@linux-foundation.org, Randy Dunlap <rdunlap@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org,
	corbet@lwn.net, virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, kvm@vger.kernel.org, linux-aio@kvack.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC v2 01/13] mm: export zap_page_range() for driver use
Date: Wed, 23 Dec 2020 14:32:07 +0800	[thread overview]
Message-ID: <CACycT3vevQQ8cGK_ac-1oyCb9+YPSAhLMue=4J3=2HzXVK7XHw@mail.gmail.com> (raw)

On Tue, Dec 22, 2020 at 11:44 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Tue, Dec 22, 2020 at 10:52:09PM +0800, Xie Yongji wrote:
> > Export zap_page_range() for use in VDUSE.
>
> Err, no.  This has absolutely no business being used by drivers.

Now I want to map/unmap some pages in an userland vma dynamically. The
vm_insert_page() is being used for mapping. In the unmapping case, it
looks like the zap_page_range() does what I want. So I export it.
Otherwise, we need some ways to notify userspace to trigger it with
madvise(MADV_DONTNEED), which might not be able to meet all our needs.
For example, unmapping some pages in a memory shrinker function.

So I'd like to know what's the limitation to use zap_page_range() in a
module. And if we can't use it in a module, is there any acceptable
way to achieve that?

Thanks.
Yongji

             reply	other threads:[~2020-12-23  6:33 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-23  6:32 Yongji Xie [this message]
2020-12-23  8:13 ` [RFC v2 01/13] mm: export zap_page_range() for driver use Christoph Hellwig
2020-12-23 14:21   ` [External] " Yongji Xie
  -- strict thread matches above, loose matches on Subject: below --
2020-12-22 14:52 [RFC v2 00/13] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2020-12-22 14:52 ` [RFC v2 01/13] mm: export zap_page_range() for driver use Xie Yongji
2020-12-22 15:44   ` Christoph Hellwig

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