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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1783328461; 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=Y2p8nkhKN8t9mp7pTmf6Ynt4ux072QpIkTobc4ZCA18=; b=qQf4nty9xC4z4NYmopQEESA+Dhc/vwpFig0OwU9gM/SZu5cTJP6WeIJxesAzXl5XNaTW36 L4f7dZMDzYgV59NKOF5rkDbMkaV/n4dmLaWowyXXeMdCTDB4QNYgtt6/D/NeDYiqdyB3dA Qo8MthFEzhjuAcPHFnSqiL6L20VT6Sg= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 4FCBC409DD; Mon, 6 Jul 2026 09:01:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 112BF1F000E9; Mon, 6 Jul 2026 09:00:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783328460; bh=Y2p8nkhKN8t9mp7pTmf6Ynt4ux072QpIkTobc4ZCA18=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=FwoRmujMe0ome16BLJ1D9b/TMcpeiIFUYp2tOrucgFjRkQnsLoRRy+gVwGwz0lqpE gnCbDR7KeGd33Vybq/kdL73A3Q5YE1YPSt4y9nWmf+4yKY23cUeEZ0jK5hugA/V2BM n/lmz0Q5WUiQB3FsIrl3vM9vgx7QjaWWpk0HraESZhimqgPh2iOgYBn5vdZcFLJPKL /jGe1RqTf+uR0vORchLLNzz3YnK7obP+U8RcMgNM+KkPwcK0BAio3yL9eZqvRHo4/X qBPLI2aODq/zvKv7qCwZEhrrFmfOmpFA+l/e8EMw5X9hKunnZ6YKVC/VDWaG8R++ry HMFNkLNe6SONg== Message-ID: <461b067f-6fa4-4539-882f-1ee6fbca5583@kernel.org> Date: Mon, 6 Jul 2026 11:00:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] userfaultfd: wait on source PMD during UFFDIO_MOVE To: Usama Arif , Andrew Morton , baohua@kernel.org, baolin.wang@linux.alibaba.com, dev.jain@arm.com, lance.yang@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, npache@redhat.com, ryan.roberts@arm.com, ziy@nvidia.com, aarcange@redhat.com, shakeel.butt@linux.dev, hannes@cmpxchg.org, riel@surriel.com, kernel-team@meta.com Cc: sashiko-bot References: <20260705131231.1499198-1-usama.arif@linux.dev> 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: <20260705131231.1499198-1-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 2BFEC4000D X-Rspam-User: X-Stat-Signature: tkupgkb16i3goqjdthizp3kwgtnetsxa X-Rspamd-Server: rspam03 X-HE-Tag: 1783328460-230822 X-HE-Meta: U2FsdGVkX19TUwTh5Gea19/F8NNpfTSnRKMHPBdfaXCjnsrUIXr7grJQwcC38QlaXds9LIABVhcjGut61EoMbOZaG/dGcdIwJN5TpOsPhZKhw6NENAj8GI6MPAoSTN+iwub6qwmnZsYhX6PKG/XxFDpigHHMWkiY8yAc6vjlcMRlUCb+GffI+yamxMMUQhfyc6dDK8XKq7J2pWb/31mXjgYLuzFuyi+jK+zGy+0uXmN42BC5nm+tlXSP56RPmZ1N3eGCys36uzxDHOgI4oc3N/gLEniwLmMDAuRDMVJnVf1g5ANnUcZCSNNZLgAg35+BH5Y4XPBHhGQZa/+duWey6Zbvo2NgsRo+jsPf/6x5f6Nb/sXJhMgW7rAk3lHMoxRJnzBDTdKu2m/XZYGjaWAE4dhB+tg9g4y8Lrc8OVRiXcnA12bR0RBJrTYCqCHjK3n97+ZpvFN7Y0ZfsogpGbMkmfH4db/jspjNqaiWEewPUYcVsS12n8GUw2hp/ntW157vPiklahi325gTJyENIm7vKLZ7G4Vnc4HPD2PMPFXSS0dQJJgqqR9eH7VDcb+jXJxc3GUWfmnqDqQWOu68cOm41MvftG9BRn8pq4Hf2OiHgj+8oToWN7DasMCdmWIXUOFwa5LbSsS6ExymQ52IDErPHhvJFfKezFo54baGvupItE0Rzvv2GV7BZujNo0Gn/H+7MWq5Z1lRtfNsTEpWR8s1E+UWspmkMCBwX9pOGdNpZZk0CaqbvbfPoaX3ZxD7lPv51z0UA9MlYAQgmp9HrV4GYv3tQF8alJ1WpfG2sKRy35pVCUC//19NktLoqcIpCrIGBH7VI0sUFSiL0pCtz9icaIsy0Ba9LhfKONC5fMgm5oC/LoPGh9/RQxxSIXK10RIGvUW76U6oYcMou7M+tRK94p1DpVP11XZwOz24FlQhkOlQ8JYuKwqwLO/TFuR8nZxRdDLXUzYYERmHsgUidTC YHWdnBbH xGTwQT+Kh/YupYpyfBkHfSZtbhQpvu+h6aAsd+spnCwrZLb3HHm8YFRIgu2ydGz9uvOE+QBZyhuN+lDP1dKHPFpl/+FpB7hkGNMbH/0jChywnqgtFbVrC0YKAkx52CTsxqDwDWOnxWhh0buYV6k0wV2U63zhs8weWVYc4Cz0nQ0aYAS1zdqeMrazFc6hpCb3qygbxFU5M5fEeAf+Ak4k1pCTGzv5MR5v/ZfPbBA3SDmimd31WnP9Ylffjrc1+GNARZ63vf5XBJ3XzgA/Gj7h9ULFrSR+xwx2oAeuES02KRqE7Bf771DOzLzSZ5FzSk/m5JYYdYexFZcT1Ytx7C1lquKvrtDVbF9MpUOvKY/ZCej48Y6lUAR9u92QmnrhPFqSuYznu0uwqmNO22CA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/5/26 15:12, Usama Arif wrote: > move_pages_huge_pmd() snapshots src_pmdval under src_ptl, drops the lock, > and, for migration entries, waits with pmd_migration_entry_wait(). > > Passing &src_pmdval is wrong. pmd_migration_entry_wait() must lock and > re-read the real page-table PMD; on split-PMD-lock kernels, a stack > address also resolves to the wrong lock. softleaf_entry_wait_on_locked() > then waits without a folio reference, which is safe only while serialized > against migration-entry removal by the real PT lock. > > Pass src_pmd, matching __handle_mm_fault() and hmm_vma_walk_pmd(). > > Reported-by: sashiko-bot > Link: https://sashiko.dev/#/patchset/20260703173903.3789516-1-usama.arif%40linux.dev?part=8 > Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") > Signed-off-by: Usama Arif > --- > mm/huge_memory.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index bdd8635922f9..c0892cc533a9 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2775,7 +2775,7 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm > if (!pmd_trans_huge(src_pmdval)) { > spin_unlock(src_ptl); > if (pmd_is_migration_entry(src_pmdval)) { > - pmd_migration_entry_wait(mm, &src_pmdval); > + pmd_migration_entry_wait(mm, src_pmd); > return -EAGAIN; > } > return -ENOENT; Looks good and follows roughly what we do in __handle_mm_fault(). Acked-by: David Hildenbrand (Arm) -- Cheers, David