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 05AF91098781 for ; Fri, 20 Mar 2026 12:55:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6CD666B0088; Fri, 20 Mar 2026 08:55:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 67E5C6B0089; Fri, 20 Mar 2026 08:55:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5949C6B008A; Fri, 20 Mar 2026 08:55:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 48A616B0088 for ; Fri, 20 Mar 2026 08:55:39 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E8C5E1C1A9 for ; Fri, 20 Mar 2026 12:55:38 +0000 (UTC) X-FDA: 84566437956.20.7F06E8D Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf23.hostedemail.com (Postfix) with ESMTP id 1FA09140003 for ; Fri, 20 Mar 2026 12:55:36 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=TERs092U; spf=pass (imf23.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@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=1774011337; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=QcA8noZYHhVwOf2PLwKW/624aKucRqQo1P8kKxKrvng=; b=VOtZ4viFAuiWVqQA5Mz72sPeggyikvJrEnCKMa9YneazQqVG6Lc+MCmIdYXXx+RSaCusAc a2JFJFEufSTFe29SZTlqxxQse9RPoYqHxNfaOdX5BaAE9+/6QpQrlGQLQEPZvl3uqz3J98 iKrntoRL3FNwfNsd1KbEYrVOoqz81QI= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=TERs092U; spf=pass (imf23.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774011337; a=rsa-sha256; cv=none; b=1ESFGrgX7KMmMzLmTNwiQDT1OF8wLm/IpTK+b2y3qGnvcyzKeG10Cui+VWHaEKcDrrp9aE Vwh9qBpiMkuLxQnwTl4Kbs31e8eGLl/xxvw8gTxhfyHB/rqWku5YmYUH5ILKiaeb7j1Hxm BgGQ+1O6hz9Vimv/rpXM6ACxNJ0r+rg= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 203D943DD7; Fri, 20 Mar 2026 12:55:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98C86C4CEF7; Fri, 20 Mar 2026 12:55:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774011336; bh=x2Ny+tySB/kVv3CHXuFUaXt/pcvgPiB8gk4xB8tYNME=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=TERs092UahZEq4jjzMNizqn0nsc1Vpeb/XxyK4Grhudmgyb5fXb+fl1RtkcRuCoNj nL+HEM4DH+nMELtouqvqX2lr3HNzyjWuXDSFiKrIU8cwQ59NSHl2iyBF7OLjrY+cO3 8J6M3W8AWwpSCJWbbsnpNNIRfklviwcht5ytuaz2eAskh+67MrPzZlkiucpDGvLEeq dBfdJ0S2xZpd8DPUqn3TxND1IExaSBMlR0wK2uA1+b0hNZvyBruOGrzulE9vF+EDBL ULe9kkrQO0eXiR3hQaXan+lM/U1arWK69K+kGbHGHsc2px+5Qd5xFb8GxW4vuR5bQF /rKnzp9LGma6Q== Message-ID: Date: Fri, 20 Mar 2026 13:55:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 03/15] userfaultfd: introduce mfill_get_pmd() helper. To: Mike Rapoport , Andrew Morton Cc: Andrea Arcangeli , Axel Rasmussen , Baolin Wang , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , "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 References: <20260306171815.3160826-1-rppt@kernel.org> <20260306171815.3160826-4-rppt@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260306171815.3160826-4-rppt@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1FA09140003 X-Stat-Signature: d1rgof5xdwneb8c45org8sohrc848je1 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1774011336-725192 X-HE-Meta: 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 XyUyaN2S 1351D7rnyNzjZbj44IAjzP5LXORFdxeyz12FoZevW8m87acr7lmNxLhcw6LcLJK9LIY8/BR5p3t+CDyGsLQ/J6VbmWJh1ULy/+lr/Mxk7xC9QdqUAttkqCPoy013oz0IItBcc/koet8le6uEPepkvsHLbprrpl4D8WlwYU+MSu9+gnKKBr1BZLUoOcMYIKRTFj8CKBiGO7mRJgOb/fUfVKJSxO4vKmMXrhBj3EjOUS32q09iXVcFiON68rcWsPr3J7bDUNKJp/W7py5DPHBsVoU/7bJNZsig+cKvRBM8nAe5yIWEEW5xuTaEMbnlGVex2eZFdTafxScU8LY0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/6/26 18:18, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" Nit: "." at the end of the patch subject > > There is a lengthy code chunk in mfill_atomic() that establishes the PMD > for UFFDIO operations. This code may be called twice: first time when > the copy is performed with VMA/mm locks held and the other time after > the copy is retried with locks dropped. > > Move the code that establishes a PMD into a helper function so it can be > reused later during refactoring of mfill_atomic_pte_copy(). > > Signed-off-by: Mike Rapoport (Microsoft) > --- > mm/userfaultfd.c | 103 ++++++++++++++++++++++++----------------------- > 1 file changed, 53 insertions(+), 50 deletions(-) > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index e68d01743b03..224b55804f99 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -157,6 +157,57 @@ static void uffd_mfill_unlock(struct vm_area_struct *vma) > } > #endif > > +static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) > +{ > + pgd_t *pgd; > + p4d_t *p4d; > + pud_t *pud; > + > + pgd = pgd_offset(mm, address); > + p4d = p4d_alloc(mm, pgd, address); > + if (!p4d) > + return NULL; > + pud = pud_alloc(mm, p4d, address); > + if (!pud) > + return NULL; > + /* > + * Note that we didn't run this because the pmd was > + * missing, the *pmd may be already established and in > + * turn it may also be a trans_huge_pmd. > + */ > + return pmd_alloc(mm, pud, address); > +} > + > +static int mfill_get_pmd(struct mfill_state *state) > +{ > + struct mm_struct *dst_mm = state->ctx->mm; > + pmd_t *dst_pmd; > + pmd_t dst_pmdval; I'd just have both on a single line. > + > + dst_pmd = mm_alloc_pmd(dst_mm, state->dst_addr); > + if (unlikely(!dst_pmd)) > + return -ENOMEM; > + > + dst_pmdval = pmdp_get_lockless(dst_pmd); > + if (unlikely(pmd_none(dst_pmdval)) && > + unlikely(__pte_alloc(dst_mm, dst_pmd))) > + return -ENOMEM; > + > + dst_pmdval = pmdp_get_lockless(dst_pmd); > + /* > + * If the dst_pmd is THP don't override it and just be strict. > + * (This includes the case where the PMD used to be THP and > + * changed back to none after __pte_alloc().) > + */ > + if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval))) Can we directly switch to pmd_leaf() while touching that? > + return -EEXIST; > + if (unlikely(pmd_bad(dst_pmdval))) > + return -EFAULT; > + > + state->pmd = dst_pmd; > + return 0; > +} [...] > /* > * Sanitize the command parameters: > @@ -809,41 +838,15 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, > while (state.src_addr < src_start + len) { > VM_WARN_ON_ONCE(state.dst_addr >= dst_start + len); > > - pmd_t dst_pmdval; > - > - dst_pmd = mm_alloc_pmd(dst_mm, state.dst_addr); > - if (unlikely(!dst_pmd)) { > - err = -ENOMEM; > + err = mfill_get_pmd(&state); > + if (err) It's a bit odd that a "get" function doesn't return a PMD pointer but instead stores it in the state. Maybe more like "mfill_prepare_pmd" ? But actually you want to have a pte table. mfill_prepare_pte_table() or alternatively mfill_alloc_pte_table() / mfill_alloc_dst_pte_table() -- Cheers, David