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b=mvA/Z70Kt1JdWg9tYbtVJQb8zJvJarqaSsObCaxf4m0JRIspPMUDfKYu7NCdPEpx9 iyOfDRzvbJEKAgL7xxM4zsj0y14lm13bsZ59kI+BcdREuhoFluLhWIp6DPc2D31kJR fBfm/uQBujTHBGNLkw1UIXLeXwdHCGujOEh1ZulPdwx+33yRZb9lCeQ59WieLDSxhG g60YDYWSZ+LfxhNwAmHEwCe/P1m8n1ztq+pabXVRhpCNUOJlNo35VxGy3uHefeDKdF ryWFY9TcwTmki9tWV2JHCo2CaNVUZ9t9YfsENzKAepQ82VC8W7WD/F+c7E8/Zo2qkW B9mIHw6aWoQ8A== Message-ID: Date: Tue, 25 Nov 2025 09:18:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()" From: "David Hildenbrand (Red Hat)" To: Ilias Stamatis , akpm@linux-foundation.org, linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, nadav.amit@gmail.com, huang.ying.caritas@gmail.com, andriy.shevchenko@linux.intel.com, bhe@redhat.com, nh-open-source@amazon.com References: <20251124165349.3377826-1-ilstam@amazon.com> <9fdc1d1f-ce00-47ff-bdf5-66e8a511be25@kernel.org> Content-Language: en-US In-Reply-To: <9fdc1d1f-ce00-47ff-bdf5-66e8a511be25@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 3E76740003 X-Stat-Signature: p19njunisudbsh1eee9qcwpw3j684t4e X-HE-Tag: 1764058738-364897 X-HE-Meta: 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 EZsOpW/h CMhihSI81xRJb6cH3KYe8mTw94wvbR609FSjwLSs8VVZnLEoKtU74apm9qM9ereycAPgCqeRIxnN/ihRCeC+7m6uoJFisuHqZKMjNSppqBU4NvAd2z+uQuCn3scIvMazoHbQp7Bc0g/Mnnc4EHux54O6zZbQLu1VY5koeakM3Ftl5jwJo4pmCU3ta+iChubveJdeYgv81++f8ze6c7kBur18lN2XYjt2+/2gJRL2KTzL93e+o1mEUFaIV/zbwWwc7IEK9AiL3GulHiqOJ/yJA8Iujda2DsDS+k0ptnPxDbwPANkAvRUXXWRXCSu66orbHvanaoYySaD+z46r7HTyDBv4JVDR22ItPkIizqi9ucD5TjTOiyyqjqMI7Wt4yX8lSnMdrBKdDuuK4JGDjxJx++e/ZFxUtxnRwWxGXfW3Sj4SDsBw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/25/25 09:09, David Hildenbrand (Red Hat) wrote: > On 11/24/25 17:53, Ilias Stamatis wrote: >> Commit 97523a4edb7b ("kernel/resource: remove first_lvl / siblings_only >> logic") removed an optimization introduced by commit 756398750e11 >> ("resource: avoid unnecessary lookups in find_next_iomem_res()"). That >> was not called out in the message of the first commit explicitly so it's >> not entirely clear whether removing the optimization happened >> inadvertently or not. > > Remembering the history, we have some things where the top might not > fully describe what the lower levels do. > > An example is for example found here: > > Author: Dan Williams > Date: Thu Feb 16 00:36:02 2023 -0800 > > dax/kmem: Fix leak of memory-hotplug resources > > While experimenting with CXL region removal the following corruption of > /proc/iomem appeared. > > Before: > f010000000-f04fffffff : CXL Window 0 > f010000000-f02fffffff : region4 > f010000000-f02fffffff : dax4.0 > f010000000-f02fffffff : System RAM (kmem) > > The CXL Windows will certainly not match System RAM, as one example. > > How would your change affect such cases? Looking into the details, I assume, as we only check that the actual range matches, not the type, that this is fine. So yeah, that makes sense to me. I guess I removed it as part of 97523a4edb7b by accident, when I primarily wanted to remove the first_lvl parameter. Given that the above still works as expected: Acked-by: David Hildenbrand (Red Hat) -- Cheers David