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 1372B30C160; Fri, 4 Sep 2026 05:07:08 +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=1788498429; cv=none; b=bOdmpZHXKeBm63K1wLSK7SuR1dtyDnwxCv6/yCiGe/oXQu/UK50Mn9XbvDmfQtCLaGrQFLIP5J5IsrefKitT1NrbqSK+cAoWTJTAWkBtLy1IEMNQXYRX1YECa48YDEHOI4aP8oAuV80v5v3PQcYVxcvYQNFBuRSCbFWpxr+am/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498429; c=relaxed/simple; bh=X3nnNAlsjYNk2TaBGHJdlL+ECGyfj4/QrTK7lMP8Zas=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aNqVeiDurKsM8uESEx2jrG/QRbl8oWuroKVcfT3ao4ess7A9TBbMv79o2d9umCPq+66a/noAS+MV3/8UXejuFAjLYY9cpbfBCsTZqasnyKBnBiojan/Lkw/5BBdKjA9fPa2s5NL4FouTs5qj0ykmaJbxSaUSgcvvpjR3gENw/Xs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cDe2H7iw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="cDe2H7iw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74E751F00A3E; Fri, 4 Sep 2026 05:07:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788498428; bh=revPVlwi7ZMYXsmjtCZZpZgW1PGufsxaRIgwg/gy9D4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cDe2H7iwZrMklLGvO6+LRHvMsYR+PLLCQYMB5f68+CPw1wJhc3WGacRawFb6SaxyH gATmIx9qQlGhrUbhKbJtc+o2w1VS6gAn9uSGQR60cyxmtQLxPfDCFKKKtDA6VuyTa7 O4lr7j8RQCB2ZQNCNnKBXoGbJ1AL/DESzJBfy1lg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Arvind Yadav , Zi Yan , Balbir Singh , David Hildenbrand , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Andrew Morton Subject: [PATCH 7.2 059/713] mm/migrate_device: clear stale mapping after freeing swapcache Date: Fri, 4 Sep 2026 06:50:27 +0200 Message-ID: <20260904045805.159647555@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045803.810145556@linuxfoundation.org> References: <20260904045803.810145556@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arvind Yadav commit 34a00895d032a414830d41106a09329ae6c251b6 upstream. __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 Signed-off-by: Greg Kroah-Hartman --- mm/migrate_device.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -1183,6 +1183,13 @@ 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)) { @@ -1222,6 +1229,12 @@ 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;