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Tsirkin" , Jason Wang , Stefan Hajnoczi , sgarzare@redhat.com, Parav Pandit , akpm@linux-foundation.org, Randy Dunlap , Matthew Wilcox , 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 Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Dec 22, 2020 at 11:44 PM Christoph Hellwig 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