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From: Hao Li To: Andrew Morton Cc: "Harry Yoo (Oracle)" , david@kernel.org, osalvador@suse.de, vbabka@suse.cz, joshua.hahnjy@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org Subject: Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug Message-ID: References: <20260330035941.518186-1-hao.li@linux.dev> <23feu42lqvc7iymgaxmnywea7c3qie5vmjm4aijbgdiazwvrcb@mmlxjowgtotv> <20260330144640.161ca53e94b37b3252de2e95@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260330144640.161ca53e94b37b3252de2e95@linux-foundation.org> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Stat-Signature: z1hxwuueadg979x5gqz9dj9fsenykppb X-Rspamd-Queue-Id: 4512B1A000A X-Rspamd-Server: rspam09 X-HE-Tag: 1774931101-975250 X-HE-Meta: U2FsdGVkX19nayXKmJOcnbMSwST0ctrL5VT/rU5mslvVANyA5WOm6YbBkJDzbmS4EhIOAD6WzXTHdOhPEapzKS//7ynounUp3g/caIeKVpbWhRMMYkPu66aqlejjZBPCbqyDE2Bu4Ka8RfS1KTWFBr158IBW9grdxkIvGPopdUjQgWmOqGUUo3Cy/ybnjWoQWK96ONeXn9w0rLseX+o36kge+UXA8R4Mno4Bs0KqluxJMj+5VEjEys9HuI9s3LrT48UUSPzhX7f2U3/MLe3zkffcWP/u1eOX3DrcyxrxtgM0CXlV2WqEYFdUVAX+ctfrxfw6+TxobrPoaKKugQ4dqmBkO4WGzd2UNxIBA58LM/Hevq8MgXMKCaww01j+Ki75J9vJWXY5dr6Zwz8j8Nzd1IsnoMBFLrRfgcQMbYW8EoereGyLoMTfiH09alxcYJxbNxWA8QXsNkMGSdHZklQsXci62zutExaeH/IjaMUb9K2pTsdS4LQeqtDkg++qpB0DldfTpDWNVy40lMnuKmF8EDbPBdTEjdRHnyeapqWsx2hyjVOjCEaeX3Yl2QwKM9amXSTu/sXXuvO+ftqWeopQdG00r2jj4U8kURIDBxofg5uQJ/mayFuxnmSik/8CJ0nN2g8dFmX3GIrSHCmLZ5mYvVf+vI2xwLEPGWNX4X86x3XF6I45bxVeHWjgYKdTYeMYSlzONPs+AfcczPDmngoRfa5UahtHnoBMgvSAyiigi560cX3FvDMe5sODXrDrf5xw7D3wVzUSry5vyNaxLAM9S2/EfM4bcqaSMl3rp1DHf8Xo7heYeluurllq469nvsOVv09+RCIf79gXtwpYrUjos/urndboh4+3/3nuwdHX3m4rLvgdqxQMOIeJTThPLRsYjA9aHc++B/zQ4AuYTBe5/e+PDnfRIBaXl9enqkQZpWUfrjP5ipnjH3VJ/6mMgBgZLTt48MEwIEPlBpQFhkf HKwx44ci y2xyM0EF+gmltMPLTXlr9scfmmg8Fx1MJ5jw1S92aihGPHT8gt+f3o3zzBOOF911pcegEAiC93ni0pi3NLOMmrEPL3febPn+Mmzjq/GRbmc6ozZ8czClVqIr8hZ2ezyuiGEBbkZXJFis+NlomR0Zkc4RD/ukkKCY8IQehCgG/D5KY+GNmNIvcuM78S8qplOZcCbUI92onLI3LCnpQZdbnKKsURVl8ljLY5nzqvfyAAJsU4RyrP4h9SNYg3gzQKsIL7c3fUAJ4EVTU0gas6uVUooDYrXcg/46hCKWku/Ro4zlcvzwffs4ugwplmkRghdl/vRnPz/DK522wZnDG/gjU2UmjiA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 30, 2026 at 02:46:40PM -0700, Andrew Morton wrote: > On Mon, 30 Mar 2026 17:34:21 +0800 Hao Li wrote: > > > > > Current users that benefit include list_lru, zswap, nfsd filecache, > > > > hugetlb_cgroup, and has_normal_memory sysfs reporting. > > > > > > > > Fixes: 8d2882a8edb8 ("mm,memory_hotplug: remove status_change_nid_normal and update documentation") > > > > > > The Fixes: tag indeed looks correct to me. > > > > > > By the way, MM needs an explicit Cc: stable@vger.kernel.org for backporting. > > > > > > Since this commit was introduced in v6.17 and we have v6.18 as LTS, > > > this should to be backported to v6.18. > > > > I had gone back and forth on whether to add the Cc tag, but I'm happy to > > include it now! > > That's OK, I'm very cc:stable-vigilant. Thanks, I'll get this upstreamed during > this -rc cycle. Thanks! > > I do like our cc:stable patches to include a clear description of the > userspace-visible impacts of the bug. Two reasons: > > - To explain to -stable maintainers why we're requesting the > backport. If they care. Heck, and to explain to me why I'm doing > this! > > - To help out someone who is using an older kernel (there are many) > who is dealing with a bug report. They're looking at this changelog > thinking "hm, I wonder if this patch will fix that bug". Let's add a > few words in there to help out with their pattern matching. Agreed, and thanks for spelling out the rationale! > > So, and not for the first time ;), what are the userspace-visible > runtime effects of this bug? > The most visible effect is that /sys/devices/system/node/has_normal_memory does not report a node even after that node has gained normal memory via hotplug. Also, list_lru-based shrinkers can undercount objects on such a node and may skip reclaim on that node entirely, which can lead to a higher memory footprint than expected. Feel free to fold the above into the changelog if useful :) -- Thanks, Hao