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 69BC936606A; Mon, 11 May 2026 12:22:34 +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=1778502154; cv=none; b=hdR7S3QkrQalcW27ATVQWPDnaxyevln/ewMvO4javEODSQzNhgCvnmH8HeKSbzqgnbv8VGBxYhnbp96hnAnPOsE1uNg79+vGviFz4sw7CuBLd84ADHBoGeKUhlN6RqeAJsBNu+TFPQ+xnBXHUZlTNY3/6EdEGFFo5BW5hNvKEJs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778502154; c=relaxed/simple; bh=2rnwGRjBmZwkmLDXWbAeEC18DQrH8JRTazD+yQeB2OQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=G7Yf7qlpJsxotZGFcsTBLFg8lMQ6F74GAI6ZjawmjcLY4FyuNXnmD22Qlb4xLyYSI218NhSQlXXdBqFvHvsIBsqYFyFehj+/I5L3G4MWKRX5fsXODBPVMePob9G8NIAAUqHShz3qpkk1zi/3jVyZUxqNfOb0XtTzCwVHnPV1kKg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DmpuWN7u; 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="DmpuWN7u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B9B0C2BCB0; Mon, 11 May 2026 12:22:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778502154; bh=2rnwGRjBmZwkmLDXWbAeEC18DQrH8JRTazD+yQeB2OQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=DmpuWN7u/aNBrVr6S4NCkSG90RyEDQAwy7lT0bv9sOkf4cV9XeoheC1A+79QFzc77 2g7hKN8WPGTp1DiUYRMLZJ038Z+LDME0/WD0UKJv9UXsKa/GZ+TVjIAB+SDrElauVB HED6EoEQjsgmKHoQIRxXQaOnzwQvWJIbgJPIpJ9jv1Kj4+8NLmgiswpBngzzgFIgcq OLERCeDC3g2q0BNmFYtvjbpUtiziHBsc2tgUuOjRrbvQgl9n6EJAcywhaaeeBHVuQK aE2qXLF/yKnZQC1yR375kwEolGQq8uzvLq/uMJzP1bQYrz3z8kGnWPx1H4d/QGHYAE dHKRtKsmaCJIw== Message-ID: <2841f424-580c-48c6-bb26-de30e4397b7f@kernel.org> Date: Mon, 11 May 2026 14:22:28 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drivers/base/memory: make memory block get/put explicit To: Muchun Song , Oscar Salvador , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , linux-mm@kvack.org, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, muchun.song@linux.dev References: <20260511111800.2181785-1-songmuchun@bytedance.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: <20260511111800.2181785-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/11/26 13:18, Muchun Song wrote: > Rename the memory block lookup helper to make the acquired reference > explicit, add memory_block_put() to wrap put_device(), and collapse the > redundant section-number wrapper into a single block-id based lookup > interface. > > This makes it clearer to callers that a successful lookup holds a > reference that must be dropped, reducing the chance of forgetting the > matching put and leaking the memory block device reference. Better mention some of the other changes here, like removing find_memory_block(). [...] > unlock_device_hotplug(); > diff --git a/include/linux/memory.h b/include/linux/memory.h > index 5bb5599c6b2b..29edef1f975c 100644 > --- a/include/linux/memory.h > +++ b/include/linux/memory.h > @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size, > void remove_memory_block_devices(unsigned long start, unsigned long size); > extern void memory_dev_init(void); > extern int memory_notify(enum memory_block_state state, void *v); > -extern struct memory_block *find_memory_block(unsigned long section_nr); > +extern struct memory_block *memory_block_get(unsigned long block_id); While at it, please drop the "extern". > +static inline void memory_block_put(struct memory_block *mem) > +{ > + put_device(&mem->dev); > +} > typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *); > extern int walk_memory_blocks(unsigned long start, unsigned long size, > void *arg, walk_memory_blocks_func_t func); > @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid); > typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *); > int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func, > struct memory_group *excluded, void *arg); > -struct memory_block *find_memory_block_by_id(unsigned long block_id); > #define hotplug_memory_notifier(fn, pri) ({ \ > static __meminitdata struct notifier_block fn##_mem_nb =\ > { .notifier_call = fn, .priority = pri };\ > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 462d8dcd636d..890c6453e887 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size) > struct vmem_altmap *altmap = NULL; > struct memory_block *mem; > > - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start))); > + mem = memory_block_get(phys_to_block_id(cur_start)); > if (WARN_ON_ONCE(!mem)) > continue; > > altmap = mem->altmap; > mem->altmap = NULL; > - /* drop the ref. we got via find_memory_block() */ > - put_device(&mem->dev); > + memory_block_put(mem); Would guards come in handy here? In general Acked-by: David Hildenbrand (Arm) -- Cheers, David