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b=udKdOqVGE7twa4wsV/WME0ZgmzBxDsuJltPh8za6s3sw3PeFVrz927G6vaA2WVq2W iZctCtcQFJ5OEae7twJ3AQpNQ3OjUEKiN5ZTNaP6JTn2neCDx8OLoFmhjyXXeRBE4c txUnSJ2LsLSsQRD3e/rqS25lU30zGAWPqjaJ9QkLpyJLGwIjtUEKk0eIiyJtNzTeZZ 0WbV6hp0l+9NmOWL4s5grW3/whTzbJItTI8N13QihXflt7V5mW16iJfcp5DyJAoyG+ 6kX1RTZuz/MiC1DtwgNA1s67dRIy4qrgXiyPd52Jkt/5Ji+3PN99LuMi1xRJ5wP5O7 AmsGeB1Xgng4Q== Message-ID: Date: Mon, 2 Mar 2026 08:42:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 4/4] page_reporting: change PAGE_REPORTING_DEFAULT_ORDER to -1 To: Michael Kelley , Yuvraj Sakshith Cc: "akpm@linux-foundation.org" , "mst@redhat.com" , "kys@microsoft.com" , "haiyangz@microsoft.com" , "wei.liu@kernel.org" , "decui@microsoft.com" , "longli@microsoft.com" , "jasowang@redhat.com" , "xuanzhuo@linux.alibaba.com" , "eperezma@redhat.com" , "lorenzo.stoakes@oracle.com" , "Liam.Howlett@oracle.com" , "vbabka@suse.cz" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "jackmanb@google.com" , "hannes@cmpxchg.org" , "ziy@nvidia.com" , "linux-hyperv@vger.kernel.org" , "virtualization@lists.linux.dev" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <20260227140655.360696-1-yuvraj.sakshith@oss.qualcomm.com> <20260227140655.360696-5-yuvraj.sakshith@oss.qualcomm.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: z6ampwa3qe3ugzg37jrwugez3fjxnn19 X-Rspamd-Queue-Id: D3DC5A000A X-Rspamd-Server: rspam03 X-HE-Tag: 1772437387-988597 X-HE-Meta: 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 BU4CqIaa bWKRYK7/q7T4eezeBXNkmyCsBhwo2PD/h4c4Rc8ZwTn0dojBv5B081dYST929dYYdNf+kVC0q4gmMJrlCCmDho300o2/PMvCVs1ywS/um7dEdxDZ17Z9mzAvKSKlrwflTRpXr21oAgV07lG5Q5LSVIeRpaetHQuKyxq2mY9b1Jz7fnOECteY3v1sYgGGG4fupjCyc9hnZ/qly3XQ7q+LtHWik9zeTGxc4d00LuI7bffBQUyju4SzAQgvPOvhGov9COdlaDluWsFbykEbE6ZyBa4xxjy8SgUAof71yAHy0MQdT2aOEhytQd806AhzSucVP2HEwF8gOovNiDMn4QmeiNStWTFBeEUz9O99ugZ04c5DxybZYuLdJFBcFZcbyipLHGcpWZFGulolMang= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/2/26 06:25, Michael Kelley wrote: > From: Yuvraj Sakshith Sent: Sunday, March 1, 2026 7:33 PM >> >> On Fri, Feb 27, 2026 at 09:50:15PM +0100, David Hildenbrand (Arm) wrote: >>> >>> No need for the (). >>> >>> Wondering whether we now also want to do in this patch: >>> >>> >>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c >>> index f0042d5743af..d432aadf9d07 100644 >>> --- a/mm/page_reporting.c >>> +++ b/mm/page_reporting.c >>> @@ -11,8 +11,7 @@ >>> #include "page_reporting.h" >>> #include "internal.h" >>> >>> -/* Initialize to an unsupported value */ >>> -unsigned int page_reporting_order = -1; >>> +unsigned int page_reporting_order = PAGE_REPORTING_DEFAULT_ORDER; >>> >>> static int page_order_update_notify(const char *val, const struct >>> kernel_param *kp) >>> { >>> @@ -369,7 +368,7 @@ int page_reporting_register(struct >>> page_reporting_dev_info *prdev) >>> * pageblock_order. >>> */ >>> >>> - if (page_reporting_order == -1) { >>> + if (page_reporting_order == PAGE_REPORTING_DEFAULT_ORDER) { >>> >>> >> >> Sure. Now that I think of it, don’t you think the first nested if() will >> always be false? and can be compressed down to just one if()? > > I don't think what you propose is correct. The purpose of testing > page_reporting_order for -1 is to see if a page reporting order has > been specified on the kernel boot line. If it has been specified, then > the page reporting order specified in the call to page_reporting_register() > [either a specific value or the default] is ignored and the kernel boot > line value prevails. But if page_reporting_order is -1 here, then > no kernel boot line value was specified, and the value passed to > page_reporting_register() should prevail. > > With this in mind, substituting PAGE_REPORTING_DEFAULT_ORDER > for the -1 in the test doesn’t exactly make sense to me. The -1 in the > test doesn't have quite the same meaning as the -1 for > PAGE_REPORTING_DEFAULT_ORDER. You could even use -2 for > the initial value of page_reporting_order, and here in the test, in > order to make that distinction obvious. Or use a separate symbolic > name like PAGE_REPORTING_ORDER_NOT_SET. I don't really see a difference between "PAGE_REPORTING_DEFAULT_ORDER" and "PAGE_REPORTING_ORDER_NOT_SET" that would warrant a split and adding confusion for the page-reporting drivers. In both cases, we want "no special requirement, just use the default". Maybe we can use a better name to express that. -- Cheers, David