From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B448235C6B1; Fri, 31 Jul 2026 20:27:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785529630; cv=none; b=S4BNkcbvb4GSznGg2wKdn2Hm500ikR24Hn+r9g9wMuGzABFOqrHV7v73m1uBVGAVQnfREd/xI5r8y/RD5gfAp+9tHPGm/OoYWauRMxx9X00uq/p5ywfMTbU+lTqcESVygyRuO4C3HD+NRiD9BM2rCu5M9Xy9Pa/U8HHoUojODA8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785529630; c=relaxed/simple; bh=j5Wnni0o7pDf9FErERx32yx7I0sacfz1onZG30n99tI=; h=Date:To:From:Subject:Message-Id; b=YvTbJ7zMSz8G+2BltFNm59iIkXXtef8cbeN3cfNLq2zADo0jIdXex9R4mKhN9M3fWRbBemUfPOG69xkQ+ohSrbKm3FsJUeK1iloqBSit+Qm9DLU9nBBAVCrCZWHvLOyQwDTKnx36VtfJ4etrMrqygaH1WXNKBzHDORoJmAFOV/o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=rSIenmwg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="rSIenmwg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2665E1F00AC4; Fri, 31 Jul 2026 20:27:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1785529629; bh=5VHnpe3FL7rg/AiAR5aYmqYcm+0NlC5kAyCqrzF5v7s=; h=Date:To:From:Subject; b=rSIenmwgQb2WA1UcvUYrv7qzNBLjCHhuLXvFcznURfm1vTUbtKECnb//JI8Bcgizn mdjHPTaTB2LiGYe6vynBazQWY864QYyASPc7r66clNF00CbNljb1tET3dfCQe26eO7 XlDj3JeANBQvCsE7mDsDd55YiRMKdgw+Xp0kOuiU= Date: Fri, 31 Jul 2026 13:27:08 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,ying.huang@linux.alibaba.com,stable@vger.kernel.org,rakie.kim@sk.com,matthew.brost@intel.com,joshua.hahnjy@gmail.com,gourry@gourry.net,david@kernel.org,byungchul@sk.com,balbirs@nvidia.com,apopple@nvidia.com,arvind.yadav@intel.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-migrate_device-clear-stale-mapping-after-freeing-swapcache.patch added to mm-new branch Message-Id: <20260731202709.2665E1F00AC4@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/migrate_device: clear stale mapping after freeing swapcache has been added to the -mm mm-new branch. Its filename is mm-migrate_device-clear-stale-mapping-after-freeing-swapcache.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate_device-clear-stale-mapping-after-freeing-swapcache.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Arvind Yadav Subject: mm/migrate_device: clear stale mapping after freeing swapcache Date: Tue, 28 Jul 2026 11:58:32 +0530 __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 use the mapped-folio path for a folio that is no longer in swapcache. It can then operate on swap_space.i_pages with invalid reference accounting, eventually triggering a folio reference count BUG. After a successful split, nr still contains the number of pages in the original large folio, although each resulting page is now a separate order-0 folio. Reset nr to 1 so each split folio is processed separately, including its own swapcache removal and mapping lookup. Refresh the saved mapping after folio_free_swap() so the current folio state is used during migration. Link: https://lore.kernel.org/20260728062832.1107127-1-arvind.yadav@intel.com Fixes: df263d9a7dff ("mm/migrate_device: try to handle swapcache pages") Signed-off-by: Arvind Yadav Reviewed-by: Zi Yan Reviewed-by: Balbir Singh Cc: David Hildenbrand Cc: Matthew Brost Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Signed-off-by: Andrew Morton --- mm/migrate_device.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- a/mm/migrate_device.c~mm-migrate_device-clear-stale-mapping-after-freeing-swapcache +++ a/mm/migrate_device.c @@ -1193,6 +1193,13 @@ static void __migrate_device_pages(unsig MIGRATE_PFN_COMPOUND); goto next; } + + /* + * reset nr so that only first after-split folio + * is processed below + */ + VM_WARN_ON_ONCE(folio_test_large(folio)); + nr = 1; } else if ((src_pfns[i] & MIGRATE_PFN_MIGRATE) && (dst_pfns[i] & MIGRATE_PFN_COMPOUND) && !(src_pfns[i] & MIGRATE_PFN_COMPOUND)) { @@ -1232,6 +1239,12 @@ static void __migrate_device_pages(unsig folio = page_folio(migrate_pfn_to_page(src_pfns[i+j])); newfolio = page_folio(migrate_pfn_to_page(dst_pfns[i+j])); + /* + * folio_free_swap() removed the folio from the swap + * cache. Refresh the saved mapping before migration. + */ + mapping = folio_mapping(folio); + r = folio_migrate_mapping(mapping, newfolio, folio, extra_cnt); if (r) src_pfns[i+j] &= ~MIGRATE_PFN_MIGRATE; _ Patches currently in -mm which might be from arvind.yadav@intel.com are mm-migrate_device-clear-stale-mapping-after-freeing-swapcache.patch