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Mon, 28 Sep 2026 08:03:07 +0000 X-Mizu-Trace-ID: 6cea94b206c11561 X-Migadu-Flow: FLOW_OUT Date: Mon, 28 Sep 2026 16:01:16 +0800 From: Dave Young To: "David Hildenbrand (Arm)" Cc: David Carlier , akpm@linux-foundation.org, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, baoquan.he@linux.dev, 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, kexec@lists.infradead.org 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: rspam08 X-Rspamd-Queue-Id: C0F3E40011 X-Rspam-User: X-Stat-Signature: wfcoyfziczjsufimkwdp8hyhkye8de1e X-HE-Tag: 1790582592-952298 X-HE-Meta: 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 hdwWDp2I f47McvAGULJ2dJSDTf+0fInRL+XJdjbS1BN9rJwKBH5vsVzu3yjAKkdjQiOzid7EGVr2MUins9RoI4zzL7mRZ+feCF0li2DYIiFBLNG8h5jilumHsNZzlj5d1dPfAi2yNxUbDzGwOeb53dSxyGdfVCPOnm/iNeIuLY3JCRMOUOq/EfTKyCKHqptbytLotgupg5YtTGCBfDmliiu8dsLo/vlCiCVp2eubnZ2GPZBcy78O0jt8sbGFOQeinLy5MWDZb813nyF26dN6VfwJ7kZGTMGRATnTbSELoVtfFwRUdB7V89qUx8RGvYZOjUiglZ7EHiqAHdccZePscxa4LIX8TTi+0sQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Cced kexec list. On Mon, Sep 28, 2026 at 09:28:08AM +0200, 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. > > > > > 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. Thanks David. Checking kernel internals via kernel version is not a good idea due to the downstream kernels. > > -- > Cheers, > > David