From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3524F3A5E9B for ; Tue, 17 Mar 2026 10:01:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773741665; cv=none; b=ACOCFXbmnv1v/s075yDpki1ZjsiVPzSJmfqreqh3o7UEfDjqzoipcj5mAjx6XRXIdSE9qbxUCPzp3LQ2anF+bt7Cib17zCvg/Df5+6lEYizsCyJyfv1qOhSo2QObXJOdzHyjK8mMmoZOteSF8eHMx77KtTfEUeC+JcQBL2S9Fdc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773741665; c=relaxed/simple; bh=W38i8vvjbZN+AiiGak0qWDXsJsrvETCfz1WLCCPZXO0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=j1Qbr5XkWq5zf4X4N6mdVC4CqS0JSczpY6hyVT0xWoNWNzduZzSCzqmlTynJDm4TYp8ug1M1Pm4b+0PQrvJdd6w+VuipvsGUCgY5gkzPqp4kczAJ+xKjQ/psbF9OHi9PmJ+Q5WF68Bt1+5eWoab/tqwARjYxp3+8LN/RFwTGRcg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g9eGZhk3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="g9eGZhk3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4571C19425; Tue, 17 Mar 2026 10:01:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773741664; bh=W38i8vvjbZN+AiiGak0qWDXsJsrvETCfz1WLCCPZXO0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=g9eGZhk3fTtR6+ndXqG8kvzQjFIhzRp1E02ekngW2oB7e2cNJRw5T6WNOrYwgjwUa n2nWulFFA2n25QOq4h4JFnz92S2ensxUIAUVhqalaYgleAaOv6n98uO4winsqIss4p 0kGgaW/LOfVXWvEQ2HWA66B4rmUhCNCVEVz4J/2ubAgVxeIUXh0CWsJ4kROyNMnAfB PXbCjDcLH59b/0rxH02rj9TOgRva8ffZYt0/gq7AWrY9lUOcRaYIiUQT51YQJcppC0 ZUZvmgm/E5+w87mrAa7TqPHMW4daxIRnJxcdgFN4CTtSbvWyS54pOs6kBGt//F5K9Z h/RtSHVLwZ3jg== Message-ID: <46d9173e-98cd-4f59-b0f3-e477afd5283b@kernel.org> Date: Tue, 17 Mar 2026 11:00:59 +0100 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 v2 5/7] mm: list_lru: introduce caller locking for additions and deletions To: Johannes Weiner , Andrew Morton Cc: Shakeel Butt , Yosry Ahmed , Zi Yan , "Liam R. Howlett" , Usama Arif , Kiryl Shutsemau , Dave Chinner , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260312205321.638053-1-hannes@cmpxchg.org> <20260312205321.638053-6-hannes@cmpxchg.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: <20260312205321.638053-6-hannes@cmpxchg.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/12/26 21:51, Johannes Weiner wrote: > Locking is currently internal to the list_lru API. However, a caller > might want to keep auxiliary state synchronized with the LRU state. > > For example, the THP shrinker uses the lock of its custom LRU to keep > PG_partially_mapped and vmstats consistent. > > To allow the THP shrinker to switch to list_lru, provide normal and > irqsafe locking primitives as well as caller-locked variants of the > addition and deletion functions. > > Signed-off-by: Johannes Weiner > --- > include/linux/list_lru.h | 34 +++++++++++++ > mm/list_lru.c | 104 +++++++++++++++++++++++++++------------ > 2 files changed, 107 insertions(+), 31 deletions(-) > > diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h > index fe739d35a864..4afc02deb44d 100644 > --- a/include/linux/list_lru.h > +++ b/include/linux/list_lru.h > @@ -83,6 +83,40 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru, > gfp_t gfp); > void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent); > [...] > static inline struct list_lru_one * > lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg, > - bool irq, bool skip_empty) > + bool irq, unsigned long *irq_flags, bool skip_empty) > { > struct list_lru_one *l = &lru->node[nid].lru; > > - lock_list_lru(l, irq); > + lock_list_lru(l, irq, irq_flags); > > return l; > } > #endif /* CONFIG_MEMCG */ > > -/* The caller must ensure the memcg lifetime. */ > -bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, > - struct mem_cgroup *memcg) > +struct list_lru_one *list_lru_lock(struct list_lru *lru, int nid, > + struct mem_cgroup *memcg) > { > - struct list_lru_node *nlru = &lru->node[nid]; > - struct list_lru_one *l; > + return lock_list_lru_of_memcg(lru, nid, memcg, false, NULL, false); The two "bool" parameters really are ugly. Fortunately this is only an internal function. The callers are still a bit hard to read; we could add /*skip=empty=*/true). like return lock_list_lru_of_memcg(lru, nid, memcg, /* irq= */false, NULL, /* skip_empty= */false); Like we do in other code. But I guess we should do it consistently then (or better add some proper flags). Anyhow, something that could be cleaned up later. > +} > + > +void list_lru_unlock(struct list_lru_one *l) > +{ > + unlock_list_lru(l, false, NULL); > +} > + > +struct list_lru_one *list_lru_lock_irqsave(struct list_lru *lru, int nid, > + struct mem_cgroup *memcg, > + unsigned long *flags) > +{ > + return lock_list_lru_of_memcg(lru, nid, memcg, true, flags, false); And here it gets really confusing. true false false ... am I reading binary code? I guess the second "false" should actually be "NULL" :) > +} > + > +void list_lru_unlock_irqrestore(struct list_lru_one *l, unsigned long *flags) > +{ > + unlock_list_lru(l, true, flags); > +} > > - l = lock_list_lru_of_memcg(lru, nid, memcg, false, false); > +bool __list_lru_add(struct list_lru *lru, struct list_lru_one *l, > + struct list_head *item, int nid, > + struct mem_cgroup *memcg) > +{ > if (list_empty(item)) { > list_add_tail(item, &l->list); > /* Set shrinker bit if the first element was added */ > if (!l->nr_items++) > set_shrinker_bit(memcg, nid, lru_shrinker_id(lru)); > - unlock_list_lru(l, false); > - atomic_long_inc(&nlru->nr_items); > + atomic_long_inc(&lru->node[nid].nr_items); > + return true; > + } > + return false; > +} > + > +bool __list_lru_del(struct list_lru *lru, struct list_lru_one *l, > + struct list_head *item, int nid) > +{ > + if (!list_empty(item)) { > + list_del_init(item); > + l->nr_items--; > + atomic_long_dec(&lru->node[nid].nr_items); > return true; > } > - unlock_list_lru(l, false); > return false; > } > > +/* The caller must ensure the memcg lifetime. */ > +bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, > + struct mem_cgroup *memcg) > +{ > + struct list_lru_one *l; > + bool ret; > + > + l = list_lru_lock(lru, nid, memcg); > + ret = __list_lru_add(lru, l, item, nid, memcg); > + list_lru_unlock(l); > + return ret; > +} Nice. Reviewed-by: David Hildenbrand (Arm) -- Cheers, David