From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D159829E10B for ; Wed, 9 Sep 2026 17:39:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788975571; cv=none; b=HvOSvWOfrHawW8xZivQJ4Qd5S87U03Nf2+3Z8e7wVEQBq8MAe4s6TJa2PkmqdwOur1+p9fC2RhfFYtfX0CIAwexubiThgB8fiL674+QCEAbtwAE2ZpE37v2oO7ZlUjCa9JO62rhjf83asvFZX6YsEhZ464+b9BLB8fQYCBPZ2Cs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788975571; c=relaxed/simple; bh=7FwEWFHDxkKSYOpv0EWYcsPgtcwKPTmELmxDIynX/5U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XlMRKHbqztd477NuG39CGUl7tlm4SvnER8TQMRbJmtegG+IxtsiJlPsIM4Q889rWKylj6CPIHUIBEYahdKUJsULosMf2fEuuNr/74oc7B2fbL98j0ezdA42PUenkH8R79Q5eczuqMEmKlza5RCRRG5+RUgsdy8BRyM8BYHuTT48= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MD1sgUCp; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MD1sgUCp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 528591F000FF; Wed, 9 Sep 2026 17:39:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788975569; bh=lckkvQ96etQRK/jiBHaJOZl8yzGvIy0G7bi8kXAAjKE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=MD1sgUCp7ahRANqwb9B3UoldMvPtufo5A6BpPQYcYs/ujUC6lNKBpgfTf5cncrxx+ M7FZaCSNNmJLs6zuogEfmbn/2Tf5sbkMkvfeMEElL4soC4xOiyUU67o0inDM/ffssf mUtENC1EA/a8YRubyznqR+NQhKXWUItgYr3KK+hTSQ2S3LPewGll3v/F20ErJaOAd5 53hbLnDjPCFl0h69kxMTQO9kEI0PjYkcH7TZ2Etjcc0q7axb1ilAEkydilez/s93cz 2WTEfJvfPU/1wFekPc94lQVAU9ym0sYYPTX5HSWyjI/2tCJtJq6eeVFGSXHL8Tveo7 vBGtc/2uJj5/w== Message-ID: Date: Wed, 9 Sep 2026 19:39:19 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 06/17] mm/huge_memory: consolidate irq and locking for folio split To: kasong@tencent.com, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Chris Li , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Yeoreum Yun , "Kiryl Shutsemau (Meta)" , Shivam Kalra , Kairui Song References: <20260908-swap-thp-cleanup-v4-0-b532a3f20e71@tencent.com> <20260908-swap-thp-cleanup-v4-6-b532a3f20e71@tencent.com> 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: <20260908-swap-thp-cleanup-v4-6-b532a3f20e71@tencent.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/7/26 20:12, Kairui Song via B4 Relay wrote: > From: Kairui Song > > Let each split helper handle its own locking instead of relying on > the caller, so both helpers manage their own irq and locking state. > This lets __folio_split() drop its local irq handling and fail label, > preparing for further cleanup. > > The file path now uses xas_lock_irq() instead of local_irq_disable() > with xas_lock(). The two are equivalent on non-RT, and > TRANSPARENT_HUGEPAGE cannot be enabled on RT anyway. This conversion > also buys consistency: every other place in mm/ that freezes a folio > while it is still reachable through the page cache already takes the > lock this way. This was actually the last plain xas_lock() on > mapping->i_pages left in mm. If we are going to support RT, spinning > on frozen folio refs could be a problem, but it already exists in > many places and should be fixed generically. > > The anon helper keeps a single local_irq_disable() as before, because > it has to cover several plain spinlocks at once. > > The dropped xas_reset() was a no-op as the xa_state is not walked > before the xas_load() under the lock. > > Reviewed-by: Zi Yan > Reviewed-by: Kiryl Shutsemau (Meta) > Reviewed-by: Yeoreum Yun > Signed-off-by: Kairui Song > --- [...] > if (nr_shmem_dropped) > shmem_uncharge(mapping->host, nr_shmem_dropped); > @@ -4390,8 +4391,6 @@ static int __folio_split(struct folio *folio, unsigned int new_order, > */ > int folio_split_unmapped(struct folio *folio, unsigned int new_order) > { > - int ret = 0; > - > VM_WARN_ON_ONCE_FOLIO(folio_mapped(folio), folio); > VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio); > VM_WARN_ON_ONCE_FOLIO(!folio_test_large(folio), folio); > @@ -4400,11 +4399,8 @@ int folio_split_unmapped(struct folio *folio, unsigned int new_order) > if (folio_expected_ref_count(folio) != folio_ref_count(folio) - 1) > return -EAGAIN; > > - local_irq_disable(); > - ret = __folio_freeze_split_anon(folio, new_order, &folio->page, > - false, NULL, SPLIT_TYPE_UNIFORM); > - local_irq_enable(); > - return ret; > + return __folio_freeze_split_anon(folio, new_order, &folio->page, > + false, NULL, SPLIT_TYPE_UNIFORM); Yeah, that bit looks especially nice. Acked-by: David Hildenbrand (Arm) -- Cheers, David