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b=YYLVcaSBRG4xJEz/Rj5RCArRccKxu5I83sxBKYg3SUXDyDQhQTIBKKyXfAHw3V+wK dccoYnxI9aXpX9Y0V18K+LBC60yXhl4bgOYwB9RefCtlhO2bnYg3P8SZaUnldUjzqb fuboSj9kpm3xEEKLqoDRmbXzubxavL0mWbSzVfnc= Date: Fri, 24 Jul 2026 21:43:07 -0700 From: Andrew Morton To: Arvind Yadav Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, ziy@nvidia.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, Balbir Singh Subject: Re: [PATCH v2] mm/migrate_device: Clear stale mapping after freeing swapcache Message-Id: <20260724214307.a50ed52cf78fdc73bc42f9bf@linux-foundation.org> In-Reply-To: <20260724082702.2531024-1-arvind.yadav@intel.com> References: <20260724082702.2531024-1-arvind.yadav@intel.com> 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-Rspamd-Queue-Id: 484CDC0002 X-Rspam-User: X-Stat-Signature: 7y66uip1nn3z5c594w3hxtfkhiixdpzm X-Rspamd-Server: rspam04 X-HE-Tag: 1784954589-36672 X-HE-Meta: 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 lRpOeYVX d8TkclcdfAkktMXbuD0tjp20u9RoUkSjFhbhKr+UcYn/M98pSpZ6p8ghxCFgwUxYSWZ/c20oTt+Er0Js6QAoMdO9bWi1kUlpz3Zk07CGFqaKTdiCp5pg8WSSbydbTO+5QUgDPwd7QHg5LHSWIHIV40YFld07SoiASCCPNg1xMq3R4yoCkbdNtjx3H/QhGsMSynJWDJyANf58VtDHi0ydJwMQ2BaOg1qRgRu8IrldOQLP/TSGEQzZJ6MO7dCSnZLYWnk0MS7OGVQiNe+7l7IFHJMK7mlQyDG0Lhl/1fK7uEOs3CcBN0GY7vP8KmYL6D4ay0zS0eyzMIKeYA3vSdxMCpT7bHXjPdlo6Vf3m6nJkzQS66xmx1T0R/lHOdqCwlM0DjHkypUTz9p8qQfIR5/9bUWke1BSZTq4prvV1Tw/6GXsdavHdsIBdis1xuA9jAoM3dfgrnOpnH9ho68bGVtdeZ1leJwW9QgKSjeXx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 24 Jul 2026 13:57:02 +0530 Arvind Yadav wrote: > __migrate_device_pages() reads the folio mapping before calling > folio_free_swap(). When folio_free_swap() succeeds, the folio is removed > from the swap cache, but the saved mapping still points to swap_space. > > Passing the stale mapping to folio_migrate_mapping() makes it take the > mapped-folio path after the swapcache reference has been dropped. This can > cause an invalid swap_space lock access followed by a folio reference > count BUG. > > Refresh the saved mapping after folio_free_swap() so the current folio > state is used during migration. > Thanks. AI review might have found an issue with this. And one possible pre-existing issue in the code which Alistair and Balbir worked on. https://sashiko.dev/#/patchset/20260724082702.2531024-1-arvind.yadav@intel.com