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Date:   Thu, 17 Sep 2020 17:40:59 -0400
From:   Peter Xu <peterx@redhat.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Jason Gunthorpe <jgg@ziepe.ca>, John Hubbard <jhubbard@nvidia.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Maya B . Gokhale" <gokhale2@llnl.gov>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Marty Mcfadden <mcfadden8@llnl.gov>,
        Kirill Shutemov <kirill@shutemov.name>,
        Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
        Jan Kara <jack@suse.cz>, Kirill Tkhai <ktkhai@virtuozzo.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification
Message-ID: <20200917214059.GA162800@xz-x1>
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On Thu, Sep 17, 2020 at 01:35:56PM -0700, Linus Torvalds wrote:
> For that to happen, we'd need to have the vma flag so that we wouldn't
> have any worry about non-pinners, but as you suggested, I think even
> just a mm-wide counter - or flag - to deal with the fast-bup case is
> likely perfectly sufficient.

Would mm_struct.pinned_vm suffice?

Though now I'm not 100% certain whether all pin_user_pages*() callers are
accounting correctly upon pinned_vm.  My gut feeling is that bc3e53f682d93df67
does not convert all the old locked_vm users with page pinnings (e.g.,
mm_iommu_do_alloc, vaddr_get_pfn, etc.; didn't try harder).

-- 
Peter Xu