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Mon, 28 Sep 2026 08:32:01 +0000 X-Mizu-Trace-ID: 42d1b3bbabd087ec X-Migadu-Flow: FLOW_OUT Date: Mon, 28 Sep 2026 16:31:51 +0800 From: Baoquan He To: "David Hildenbrand (Arm)" , k-hagio-ab@nec.com, ruirui.yang@linux.dev Cc: David Carlier , akpm@linux-foundation.org, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brendan.jackman@linux.dev, dakr@kernel.org, driver-core@lists.linux.dev, gregkh@linuxfoundation.org, hannes@cmpxchg.org, jan.kiszka@siemens.com, kasong@tencent.com, kbingham@kernel.org, liam@infradead.org, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, mhocko@suse.com, osalvador@suse.de, qi.zheng@linux.dev, rafael@kernel.org, rppt@kernel.org, shakeel.butt@linux.dev, surenb@google.com, vbabka@kernel.org, weixugc@google.com, yuanchu@google.com, ziy@nvidia.com, devel@lists.crash-utility.osci.io Subject: Re: [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT Message-ID: References: <20260921-b4-sparsemem_cleanups-v2-10-54d81d65e125@kernel.org> <20260927192013.144672-1-devnexen@gmail.com> <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9093920004 X-Stat-Signature: inzm9d9ursjms31z7kyigw9w64ucyij6 X-Rspam-User: X-HE-Tag: 1790584325-654655 X-HE-Meta: U2FsdGVkX1+NeS8y/pRA6KASd5oKH3kT3w+Tm+YUbEWxwHKpg2F2XfCu/SO3WmaUhO3TG0rIG1LfDxyZOiVRhtgCpeQxPRMbw/AJG161PHegpHkb4w5MvMnWDHMvaX3o19m1qE5vvzbzunLJpNCeCKRXeqgjkHfQgRADsQcQyUr+2zofVMPZfiqjlkETRT+lsxuh1R2gMSU5C7eGE7h0ucHxaUCdf/TEbA2DUeiX0d76aYnjRdOir2Jbu5kgyQhLss/cpI4hxuoRykj76eLLqm1y9NJA6K3nIM5t6eJJrys9iWaktoN1CsN4O/6u7SsI3+t9wmwn/JA7FjvOKfQhRbErM3wZAF4fuPYlN6DmzZWJkjepbduvgE2kuhVh+5bTOt0ici09AHhSIZhcTE5kwY7LdEV4lhH2iRQLoB5TG+9Kj3+Q+pX2wdwIgORUIVvyFdjw4gaqtH3hjaPUfRjJcpUn68ALFXwP6lfamuzeT1TQyCQJQTMsebrYHbj7UKfunr/ZIzO3bE3b7ctlnQ7/j2MtBo61FhmeQC1F1yNomVEQB6lFqYo9JsnqG/0+A6O3h7VLLN0T3wd2GOuOZUGG0DWm5cvy8UFT7x11TZHdO1a2KWUnRm+nhxrX1I566impz118SFSEJv4QWSGaScRbLoiT3nQhoLmjj66PFoQJadUaOBqtjuFSUzrEhQkIu+kqpnyvFfciEDHBr1M8sP3k9FU+0YvDmKNZ2RgIHJGCDhTW5fQDzApwXoo84C598RyayfEI4JzhO4LHBH86oC04/xljKCZaG+d4wiDoHQVIWR6gfzkiePQc8JvCyyzQ7iJh8hQ/DC4JD7S3fxZQ7BITsqknCjkV7Mr0a6a4jMm4mYWRkVyr6re3KSnIkoJ25we9o8Ic3tSSyoHbI9BHHsFxq87FOXBDLdQ7Z2DO64C4RfkRBDhKZpu0mFhyKjggRpQk/KLYnOO7zjBGysZQXxG ZhpO3Twg Rx4VeItz2R3S9fw62nArxMCZYOnHrlvBQh/dTuep8Rhz0UmkDzJnMA9zOKssSfTDeo2+0E79GLkFVFZHUG8Kt1OZko+/GWDqR8F78CbqSuFESeABUjq5O3RIkF6BCSlWb/7DzrjDtQFwrYk78x1CkwkZentBICwusC7fKVbjfOODEYPoL0FL7rgPuRSbmhL8jWvg4CRUfH7KVVskUqqMyaUdAq4Gwm9+iBMEzAMl2LGJ/5m5dKZaOqpT8HPsr04TAS6zNEMUm+Ru1w6/s+DzmA3aQv2IAyexNpOw05bqFfzfufL7KOecB8/3wTcDkZ8bgcgMIkZE0CXGIzv8fv3s2JmqwTJa6JM2pxVpG2UP/4XE5dbdzj/U8IBJHg9XsMWJ7mAXa Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/28/26 at 09:28am, David Hildenbrand (Arm) wrote: > On 9/27/26 21:20, David Carlier wrote: > > On Mon, Sep 21, 2026 at 09:59:02PM +0200, David Hildenbrand (Arm) wrote: > >> enum { > >> - SECTION_MARKED_PRESENT_BIT, > >> SECTION_HAS_MEM_MAP_BIT, > >> SECTION_IS_ONLINE_BIT, > >> SECTION_IS_EARLY_BIT, > > > > Hi David, > > Hi! > > > > > It seems dropping SECTION_MARKED_PRESENT_BIT shifts the other section flags down > > one bit. crash hardcodes SECTION_HAS_MEM_MAP as (1UL << 1) in > > pfn_to_map(), so it now tests SECTION_IS_ONLINE: offline and > > ZONE_DEVICE sections no longer resolve to a struct page. makedumpfile > > only checks bit 0 and is fine. > > Thanks. To be expected when relying on kernel internals. > > Which makes me wonder why makedumpfile > (https://github.com/makedumpfile/makedumpfile) not require any such information. Makedumpfile requires it too, while it doesn't ask for HAS_MEM_MAP. So checking MARKED_PRESENT becomes checking HAS_MEM_MAP's value, it luckily works. # git grep MARKED_PRESENT makedumpfile.c: if (!(map_mask & SECTION_MARKED_PRESENT)) { makedumpfile.h:#define SECTION_MARKED_PRESENT (1UL<<0) Add makedumpfile maintainer Kazu here. And add Dave Young here since I heard he is taking over Crash maintenance as a volunteer. > > > > > Keep bit 0 reserved, or export the bits via vmcoreinfo? > We could export it, or crash can simply detect the change based on the kernel > version. I remember the latter was done in makedumpfile in the past (although we > export it). > > I can send a separate patch to export it. > > -- > Cheers, > > David