From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2397BF364A3 for ; Thu, 9 Apr 2026 17:19:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 571FA6B0005; Thu, 9 Apr 2026 13:19:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 522BF6B0088; Thu, 9 Apr 2026 13:19:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3EA566B008A; Thu, 9 Apr 2026 13:19:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 2CF856B0005 for ; Thu, 9 Apr 2026 13:19:13 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id C0173C2AB6 for ; Thu, 9 Apr 2026 17:19:12 +0000 (UTC) X-FDA: 84639678144.10.E92D456 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf12.hostedemail.com (Postfix) with ESMTP id D15B840005 for ; Thu, 9 Apr 2026 17:19:10 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=TANCjvkw; spf=pass (imf12.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775755151; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=grHbRatBeQQy256OvZuKHDLVyKgjZm55I2/EOqWEDPo=; b=F70WUpRrh2cE7VFk5khAzcsOaRkqk7XbatKg+SXoVIs1Dc1D3pJMJ7v5zlhBXQlJ/CLMYL wIKvddzNZsRSyKpDele1yw7hKpOsSom1HWP+xSQtim/EO1aG+185BZwSvY3oki+jZ65pW1 WZV2h5TlyoKL5BfotfzLZuxvmVRs2bI= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1775755151; a=rsa-sha256; cv=none; b=BA/UrfFR8Igzw+nEFwxMtRHYINEbE1EZkLkOlyMcVVAXja4xax/JEKx5fdfo23JPOheSny f/Llq+QR4k1O545U17jjwsSJSEIze50UJtduFABHcmjQ/1I7M2IxHY73jnYJHrNo2clCRv tTu4m0kleBmgoi2gzGjQgELh+Xn4rLc= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=TANCjvkw; spf=pass (imf12.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id A933D43D4A; Thu, 9 Apr 2026 17:19:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 338ACC4CEF7; Thu, 9 Apr 2026 17:19:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775755149; bh=cGMLUPOtx8qaZqawYKdm2oqkNFYMjpc+BvWqDcnrHmc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TANCjvkwBh0HGfxUlaqhwxG1wASBAqCJhrHR+iNTurVIvK7eDEUwCeDqx+t4TlRol AgdDj8kwm6Vk3GekEV/tztKEH2omKNhV816obK929+XIO7HpukmwN1iiFr8cymvieU njkaq1E3/Sa5xZ/MitYIofrgWeZ0jhhXzJVakyzoNvEFhnQrK5DfMlp+AiOm1lgCB8 BTQicRTFbKOgnCpDMGjf6/mDFFkPQH3EtMWoGjxGyMebiHPNnTvROup6Xxn1vZDVak dYrfOgpFh2ictQjcE7u6Kn4eZDIdwVV5RAyvgwIpubxVyMxTe4pQWuHa1RllwfEXUC URTq/JMPoPSpw== Date: Thu, 9 Apr 2026 20:18:57 +0300 From: Mike Rapoport To: Tal Zussman Cc: Andrew Morton , David Hildenbrand , Andrea Arcangeli , Andrei Vagin , Axel Rasmussen , Baolin Wang , Harry Yoo , Hugh Dickins , James Houghton , "Liam R. Howlett" , "Lorenzo Stoakes (Oracle)" , "Matthew Wilcox (Oracle)" , Michal Hocko , Muchun Song , Nikita Kalyazin , Oscar Salvador , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v4 07/15] userfaultfd: introduce vm_uffd_ops Message-ID: References: <20260402041156.1377214-1-rppt@kernel.org> <20260402041156.1377214-8-rppt@kernel.org> <6a171abc-ebd2-4ddf-8c36-34c66ca42043@columbia.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6a171abc-ebd2-4ddf-8c36-34c66ca42043@columbia.edu> X-Rspamd-Server: rspam12 X-Stat-Signature: bntw83hux46pfkhrtj53yucmqmwqpdns X-Rspamd-Queue-Id: D15B840005 X-Rspam-User: X-HE-Tag: 1775755150-254274 X-HE-Meta: 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 YpC165WH hh4ACa7Jn7BpTeSf1h52fQYiCLt0QI40JQjul+TSfKOqVMXdf4sgcX74brQRANLnNhSAkesDvYLvimOwem0bV+rIzvaX3KIQGTnu/BeEqZMUZQ1izOcd9aYRYQD98HsZmCK8G6jypG1VT625jTcC3fbcH3rym+gFYPnmQG75qie5wE9nYi2dVdSY6ggSjacyPio6lzDYMpLoStrXclh6tdEFEDag+D4pYW5acBwEecKJQQTCaZlDGmixP0rM8+XtoF/9M5oRVJeuJmb+UOe3ZGmTIR79cIvnXaXImFPA06VTRQIl8DR3niJe68g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 02, 2026 at 03:32:58PM -0400, Tal Zussman wrote: > Hi Mike, > > On 4/2/26 12:11 AM, Mike Rapoport wrote: > > @@ -2021,34 +2040,33 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, > > bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags, > > bool wp_async) > > { > > - vm_flags &= __VM_UFFD_FLAGS; > > + const struct vm_uffd_ops *ops = vma_uffd_ops(vma); > > > > - if (vma->vm_flags & VM_DROPPABLE) > > - return false; > > - > > - if ((vm_flags & VM_UFFD_MINOR) && > > - (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma))) > > - return false; > > + vm_flags &= __VM_UFFD_FLAGS; > > > > /* > > - * If wp async enabled, and WP is the only mode enabled, allow any > > + * If WP is the only mode enabled and context is wp async, allow any > > * memory type. > > */ > > if (wp_async && (vm_flags == VM_UFFD_WP)) > > return true; > > > > + /* For any other mode reject VMAs that don't implement vm_uffd_ops */ > > + if (!ops) > > + return false; > > + > > + if (vma->vm_flags & VM_DROPPABLE) > > + return false; > > + > > Doesn't moving the VM_DROPPABLE check after the wp_async early return make > the issue David raised in [1] possible again (i.e. moving swapbacked pages > into a droppable region using UFFDIO_MOVE)? With this change, VM_DROPPABLE > pages can now be registered with uffd under wp_async, which allows > UFFDIO_MOVE. > > I think the VM_DROPPABLE check should go right before the wp_async check. > And it would probably benefit from a comment... You are right. Andrew, if it's not too late can you please add this fixup: diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index f1828106484b..75290483ffc7 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2019,6 +2019,9 @@ bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags, { const struct vm_uffd_ops *ops = vma_uffd_ops(vma); + if (vma->vm_flags & VM_DROPPABLE) + return false; + vm_flags &= __VM_UFFD_FLAGS; /* @@ -2032,9 +2035,6 @@ bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags, if (!ops) return false; - if (vma->vm_flags & VM_DROPPABLE) - return false; - /* * If user requested uffd-wp but not enabled pte markers for * uffd-wp, then only anonymous memory is supported > Thanks, > Tal -- Sincerely yours, Mike.