From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793129528; b=L4kRFWVlB9Npb0nnJMnJNOp7eiCJGApRcaxkFeyZyR3qh1fG/jnhuWysDWUoVuCXo53C hsUmxGlakNNCrik38EiQe4ZYcm4Ci/+mm/MVKParuX42RNJMv7/WzX+HfRZWZH/wA/e0J SgO661DKSG/VEhxllHeiUdxtodi3kQtYkqQCG8OhezNezwXCeCugE4WB67Gtopn6iRceL 8QhDFpH+71HCpDBq8hgfqW0354vha2OnWbO4eFdTQ0/LQM9dMuusLlz4K32ID7+dLqjOt tq7sZlic9Z+Nqk+YsL45FhfS+5shVW1pTYdjqARRPVVx9wLFcLh45f9HUK/cVOFidpA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793129528; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=pdMKQRVfPao2Y0l/0sEvsr0YaDZON+7McqaGQOdPdzM=; b=J/6cUgrvAFv16RkbYopVTyHF+jmQNYG6zot+9uf6U76MH3t78tAWO5lgjwyMHwYxuHVU LsIRSB6/yUPuTrCrdwnO90Zxr6bH7eTNpR7vjT7UIb3VIjyjbAdByTzNa9aR1E7gbybIi CtXdqujL1Utvy9oyE7BLgun7kieVCWfzApVx5/ybcI2hc1MQnkz6eWf6iDzo+JtEptZcP ifU3a74SYOiJ4VHA3uACTcWm6G3vVen/l8gSUn1EopHjRFuotuN146FoOSgGEpSsv0F4k H0PKZXwh0mQgsCBX60VVIIboupEG+F33nJIpA5juLSrZhCm30+hY4kjWV57v0xTmLQw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=J2KOffh9; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 840E4606A31A; Tue, 27 Oct 2026 19:32:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=J2KOffh9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 256D31F01825; Tue, 27 Oct 2026 19:31:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793129528; bh=pdMKQRVfPao2Y0l/0sEvsr0YaDZON+7McqaGQOdPdzM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=J2KOffh9t5THz/aVV9AXm+zRNrOFDoRwtp977EUo1PAOBknoI8V3BnNjjtRLAE4Ru GY5GDPTQ+/81Ar3+hzwrjA0JeTMSAd3xgLXkkWNIOh4w5qNGRaWbYHgigxK1BSB0q7 ly8wspHWyvxYXk9F43GT7SewL7fEGQ0Hpa7OJz1VbSrP8w/Wv8rLA0NKXANgiBfMrD TTqIJu5xLE1Ab2vB6aGL8JXJt7kYBWgxH7cJ5Z/fmQvZq4f73ADggruc/guEar+TGR HrC4fv0DA8YODO90lZnMcUoWInit/GOljN2R28H+dA2gPH4zQmKtMA4c2HYGyd/lsp d3rkBUoXQHNBg== Message-ID: Date: Tue, 27 Oct 2026 20:31:50 +0100 X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 25/46] mm/userfaultfd: wake waiters when registration modes are removed To: "Lorenzo Stoakes (ARM)" , Gregory Price Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-25-6f74bec9a5bb@kernel.org> <179307782442.2301705.17273288326330283268.b4-reply@b4> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/27/26 09:24, Lorenzo Stoakes (ARM) wrote: > On Mon, Oct 26, 2026 at 10:10:24PM -0700, Gregory Price wrote: >> From: Gregory Price >> Subject: [PATCH] mm/userfaultfd: compare exact registration modes before skipping >> >> Changing registration from MISSING|WP to WP returns success but leaves >> MISSING enabled. The no-op check sees that WP is already set and skips >> the update, so later accesses to missing pages still wait for userspace. >> >> Skip the update only when the current and requested UFFD modes match >> exactly. >> >> Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") >> Cc: stable@vger.kernel.org >> Signed-off-by: Gregory Price (Meta) >> --- >> mm/userfaultfd.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c >> index 669f71d485d02..0a28130cebc99 100644 >> --- a/mm/userfaultfd.c >> +++ b/mm/userfaultfd.c >> @@ -2299,7 +2299,7 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, >> * userfaultfd and with the right tracking mode too. >> */ >> if (vma->vm_userfaultfd_ctx.ctx == ctx && >> - vma_test_all_mask(vma, vma_flags)) >> + (vma->vm_flags & __VM_UFFD_FLAGS) == vm_flags) > > Would be better not to regress to the legacy API. I realise we don't use it for > backported fixes in general, but this patch obviously won't apply to older > versions anyway, so we should use the correct API now, and this for older > versions. > > I'll add a better predicate probably to do this in one go, but for the fix, > I put the correct patch below. > > >> goto skip; >> >> /* >> >> -- >> Gregory Price > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index 777bf122d32a..c71cb9179913 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -2288,6 +2288,9 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, > prev = vma; > > for_each_vma_range(vmi, vma, end) { > + const vma_flags_t curr_vma_flags = > + vma_flags_and_mask(&vma->flags, __VMA_UFFD_FLAGS); > + > cond_resched(); > > VM_WARN_ON_ONCE(!vma_can_userfault(vma, vm_flags, wp_async)); > @@ -2300,7 +2303,7 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, > * userfaultfd and with the right tracking mode too. > */ > if (vma->vm_userfaultfd_ctx.ctx == ctx && > - vma_test_all_mask(vma, vma_flags)) > + vma_flags_same_pair(&curr_vma_flags, &vma_flags)) > goto skip; > > /* > > -- > Cheers, Lorenzo I now have: >From e2cb5867bd46dd6c601dfa5f0415bf7c8e12600a Mon Sep 17 00:00:00 2001 From: Gregory Price Date: Tue, 27 Oct 2026 20:27:52 +0100 Subject: [PATCH] mm/userfaultfd: compare exact registration modes before skipping Changing registration from MISSING|WP to WP returns success but leaves MISSING enabled. The no-op check sees that WP is already set and skips the update, so later accesses to missing pages still wait for userspace. Skip the update only when the current and requested UFFD modes match exactly. Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") Cc: stable@vger.kernel.org Signed-off-by: Gregory Price (Meta) [ david: apply fixup from Lorenzo ] Signed-off-by: David Hildenbrand (Arm) --- mm/userfaultfd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 710e913c73bf..24b7a2612469 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2291,6 +2291,7 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, for_each_vma_range(vmi, vma, end) { const bool any_mode_removed = vma->vm_flags & __VM_UFFD_FLAGS & ~vm_flags; + const vma_flags_t curr_vma_flags = vma_flags_and_mask(&vma->flags, __VMA_UFFD_FLAGS); cond_resched(); @@ -2304,7 +2305,7 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, * userfaultfd and with the right tracking mode too. */ if (vma->vm_userfaultfd_ctx.ctx == ctx && - vma_test_all_mask(vma, vma_flags)) + vma_flags_same_pair(&curr_vma_flags, &vma_flags)) goto skip; /* -- 2.43.0 -- Cheers, David