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b=f63X9Zu7YNmXyMUaTAFvqbxzoJkekuYETpxFg3R8skFFkLnvP8TImGjjrNDIKxr1u kRhEOHtLl62VFYWV+au5yuJFevSsPvOgEHfOxRFzDOpyR5L9pxLiAAQzO5mKK4i9vM 28yPxhXdRxpdvk7oBCvxAacSFjaKg0TsBx+xJ9KtR0cANeaHZQhepTgNJ2O97ZF10T LpA5xIevqOgnXSdDw8VwUON3/R2HMj2UewnkoFpWCXKzZJiU7vEoDv7PUWw3znKZR0 Q2mSkamufWZlZK2r6UnhfvKh+UvDzYOna3GGaMLY8DEUTqjWOrIehGx3p2HcCeLFZa e9A5Jmr1iF/bQ== Message-ID: <571547b0-007a-4cf9-be1d-95a0ef871cf8@kernel.org> Date: Mon, 2 Mar 2026 10:18:23 +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: Yuvraj Sakshith , Michael Kelley 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; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: wcbqjiur5bd1euyqhn6bzw4ahmea9hq6 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 409A6A000E X-HE-Tag: 1772443112-477371 X-HE-Meta: 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 GpePEMuV JOtETCVfLELli2ocNxpqOnaDlWZDEDbxuDymsWjpVfK9VCSQtaPvA1YwnpIZ250EaXSy52NHq+vqLGTZ0XSbjUrg7USzb0BeoWXPgRFUmqx2QCJq/KReAnuK9q5zXp+yDTHPErAlOMfn4g/fCN4kw0uEECUYieK6HoZVrypRs9Pfb5Fjp2TKemyrihMI8ZktmB8PdY7ScYouVVH/bIHH32DnnClgqlAxwyPfIK5GZcUOmF2oNHXVgYu/zxyEDO+F3HL2TMs0DCBwB5rKdewWQ80xvu+YOpUh8Da3Uz3HS1EtJDH1RxkUous6j/w6lq+ytU5I45q/nVBj6SiaqZuQQ7RoQ0oZFa63aQMcd Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/2/26 09:54, Yuvraj Sakshith wrote: > On Mon, Mar 02, 2026 at 09:09:13AM +0100, David Hildenbrand (Arm) wrote: >> On 3/2/26 09:00, Yuvraj Sakshith wrote: >>> Option 1: >>> >>> if (page_reporting_order == PAGE_REPORTING_DEFAULT_ORDER) { >>> if (page_reporting_order != PAGE_REPORTING_DEFAULT_ORDER >>> && prdev->order <= MAX_PAGE_ORDER) { >>> page_reporting_order = prdev->order; >>> } else { >>> page_reporting_order = pageblock_order; >>> } >>> } >>> >>> Option 2: >>> >>> if (page_reporting_order == PAGE_REPORTING_ORDER_NOT_SET) { >>> if (page_reporting_order != PAGE_REPORTING_DEFAULT_ORDER >>> && prdev->order <= MAX_PAGE_ORDER) { >>> page_reporting_order = prdev->order; >>> } else { >>> page_reporting_order = pageblock_order; >>> } >>> } >>> >>> >>> >>> Agreed. >>> >>> If we were to read this code without context, wouldn't it be confusing as to >>> why PAGE_REPORTING_DEFAULT_ORDER is being checked in the first place? >> >> I proposed in one of the last mail that >> "PAGE_REPORTING_USE_DEFAULT_ORDER" could be clearer, stating that it's >> not really an order just yet. Maybe just using >> PAGE_REPORTING_ORDER_UNSET might be clearer. >> > Ok >>> >>> Option 1 checks if page_reporting_order is equal to PAGE_REPORTING_DEFAULT_ORDER >>> and then immediately checks if its not equal to it. Which is a bit confusing.. >> >> >> Because it's wrong? :) We're not supposed to check page_reporting_order >> a second time. Assume we >> s/PAGE_REPORTING_ORDER/PAGE_REPORTING_ORDER_UNSET/ and actually check >> prdev->order: > Oops, typo :) I meant prdev->order. >> >> if (page_reporting_order == PAGE_REPORTING_ORDER_UNSET) { >> if (prdev->order != PAGE_REPORTING_ORDER_UNSET && >> prdev->order <= MAX_PAGE_ORDER) { >> page_reporting_order = prdev->order; >> } else { >> page_reporting_order = pageblock_order; >> } >> } >> > Great. Much more clearer on page_reporting.c 's end. > > Don't you think on the driver's end: > > prdev->order = PAGE_REPORTING_USE_DEFAULT; looks clearer? As compared to: > prdev->order = PAGE_REPORTING_ORDER_UNSET; ? > > I'm thinking, why would a driver worry about page_reporting_order being set/unset? Maybe PAGE_REPORTING_ORDER_UNSPECIFIED ? In any case, we should use a single flag for this. Everything else will be confusing once drivers could use only one of them. -- Cheers, David