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b=jURyxAjICAw+O6bXQeTFnit8oi3xSXozTg6BCrySYVh2AqIh8wiej8qRBEzJHnOky nPwsy7Li5/Pk3jr3FgbINEvo06oasgpgVbznHfwcoIedWyZhAdkHs3bSbDcPP0Aa8F FGCVPMyqBeUksPS1S3m91+b2d8QFIN6q4xZwilNY= Date: Tue, 19 May 2026 14:08:35 -0700 From: Andrew Morton To: Georgi Djakov Cc: Georgi Djakov , david@kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, Mike Rapoport , Vishal Verma Subject: Re: [PATCH v2] drivers/base/memory: set mem->altmap after successful device registration Message-Id: <20260519140835.0eb262de8c8e37b9fd307c74@linux-foundation.org> In-Reply-To: <90c0af4b-f608-42e5-9f61-222d943bcebc@kernel.org> References: <20260514092657.3057141-1-georgi.djakov@oss.qualcomm.com> <20260519132522.421c018b39328ebc4767dd8e@linux-foundation.org> <90c0af4b-f608-42e5-9f61-222d943bcebc@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 1s4x5akds4kjifbfw3cbnxb67s8zg3zd X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 28F6320003 X-Rspam-User: X-HE-Tag: 1779224917-537015 X-HE-Meta: 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 rU2wqjua IFtPllH7RH0mzgE5Q7H79Hhutk/qCiKKrRoadU+NWnrV1gdASpS0+Ww3m0ppKhrWOdhNLkU0op6n4wFZBvRATNsbqALDf5uyOIhBxmuQ2Y3uBUwZAIhs10tmYHlJ+f3U5x0TNdWiJxCaNuNDf+lszQIt12VooTncYgXqSl2lBh3qYLXV2z5/6rWC+VhEETZwnYrbg2tPnHmvQj25CbVGhGmO+PLfctufNgeQU789FwIDbAjZe6iokn1tKb4MmKmjvHIQ06j07a0T2m6kKi5owsMux1SzIqWyVJLtG8c5BH9MW0ES+Ud7SwPGJVo6NQFEzloLeGa51GOY96o9zWexaYLxpoUvGizcbVeRxspP0wWojmFZKydWqTC/8nxxhO/4IjPTn9VyfLCf+UKC7gzlVTCYWeg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 19 May 2026 23:57:52 +0300 Georgi Djakov wrote: > On 5/19/26 11:25 PM, Andrew Morton wrote: > > On Thu, 14 May 2026 02:26:57 -0700 Georgi Djakov wrote: > > > >> If __add_memory_block() fails at xa_store() (under memory pressure > >> for example), device_unregister() is called, which eventually > >> triggers memory_block_release() with mem->altmap still set, causing > >> a WARN_ON(mem->altmap). > > > > That isn't good. > > > >> This was triggered by modifying virtio-mem > >> driver. > >> > >> Fix this by delaying the assignment of mem->altmap until after > >> __add_memory_block() has succeeded. > >> > >> Fixes: 1a8c64e11043 ("mm/memory_hotplug: embed vmem_altmap details in memory block") > > > > Patch is nice and simple so I'll add a cc:stable to this, even though > > the issue seems rather minor. > > > > btw, AI review had no issue with your change but might have found a bug > > in create_altmaps_and_memory_blocks(): > > > > https://sashiko.dev/#/patchset/20260514092657.3057141-1-georgi.djakov@oss.qualcomm.com > > Yes, i have hit exactly this bug actually (shortly after this WARN_ON, we crash) > and was going to send a fix, but noticed that someone already did: > https://lore.kernel.org/lkml/20260428081855.1249045-3-songmuchun@bytedance.com/ > > I can respond with my RB on that one if you haven't applied it yet. I have indeed applied it, but a R-b isn't a problem and would be welcomed. One of the many reasons why I retain patches in quilt form for a few weeks before gitifying them.