From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C50FEC433EF for ; Mon, 7 Mar 2022 09:21:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236591AbiCGJWe (ORCPT ); Mon, 7 Mar 2022 04:22:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52510 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236585AbiCGJWG (ORCPT ); Mon, 7 Mar 2022 04:22:06 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5041F66608; Mon, 7 Mar 2022 01:20:28 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0BC14B810C2; Mon, 7 Mar 2022 09:20:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E97BFC340E9; Mon, 7 Mar 2022 09:20:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646644825; bh=PZvMsgCi9WxB8C/9nmbvpKu+4Ec0qTUjUX+o2X8/BsQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h7Kh8aWht0RgJ2Jke/CMaRj8JIyoZXkhom0WyXEIV/wiGtAZ4wg/7SxgWkadLnQ/u lAEo5/amyvM32wF+7Mk8hjwKBJTs87hK6MZ33Q9dAyap/Kt/jiz1YUo90JlNwkFLga ZuIdg35GcaoXtPzxGQXDkJExt6mDuS1oTvyfUAXI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hugh Dickins , Zeal Robot , wangyong , Mike Kravetz , "Matthew Wilcox (Oracle)" , CGEL ZTE , "Kirill A. Shutemov" , Song Liu , Yang Yang , Andrew Morton , Linus Torvalds Subject: [PATCH 4.9 31/32] memfd: fix F_SEAL_WRITE after shmem huge page allocated Date: Mon, 7 Mar 2022 10:18:57 +0100 Message-Id: <20220307091635.323434658@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220307091634.434478485@linuxfoundation.org> References: <20220307091634.434478485@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hugh Dickins commit f2b277c4d1c63a85127e8aa2588e9cc3bd21cb99 upstream. Wangyong reports: after enabling tmpfs filesystem to support transparent hugepage with the following command: echo always > /sys/kernel/mm/transparent_hugepage/shmem_enabled the docker program tries to add F_SEAL_WRITE through the following command, but it fails unexpectedly with errno EBUSY: fcntl(5, F_ADD_SEALS, F_SEAL_WRITE) = -1. That is because memfd_tag_pins() and memfd_wait_for_pins() were never updated for shmem huge pages: checking page_mapcount() against page_count() is hopeless on THP subpages - they need to check total_mapcount() against page_count() on THP heads only. Make memfd_tag_pins() (compared > 1) as strict as memfd_wait_for_pins() (compared != 1): either can be justified, but given the non-atomic total_mapcount() calculation, it is better now to be strict. Bear in mind that total_mapcount() itself scans all of the THP subpages, when choosing to take an XA_CHECK_SCHED latency break. Also fix the unlikely xa_is_value() case in memfd_wait_for_pins(): if a page has been swapped out since memfd_tag_pins(), then its refcount must have fallen, and so it can safely be untagged. Link: https://lkml.kernel.org/r/a4f79248-df75-2c8c-3df-ba3317ccb5da@google.com Signed-off-by: Hugh Dickins Reported-by: Zeal Robot Reported-by: wangyong Cc: Mike Kravetz Cc: Matthew Wilcox (Oracle) Cc: CGEL ZTE Cc: Kirill A. Shutemov Cc: Song Liu Cc: Yang Yang Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/shmem.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2478,7 +2478,8 @@ static void shmem_tag_pins(struct addres slot = radix_tree_iter_retry(&iter); continue; } - } else if (page_count(page) - page_mapcount(page) > 1) { + } else if (!PageTail(page) && page_count(page) != + hpage_nr_pages(page) + total_mapcount(page)) { radix_tree_tag_set(&mapping->page_tree, iter.index, SHMEM_TAG_PINNED); } @@ -2538,8 +2539,8 @@ static int shmem_wait_for_pins(struct ad page = NULL; } - if (page && - page_count(page) - page_mapcount(page) != 1) { + if (page && page_count(page) != + hpage_nr_pages(page) + total_mapcount(page)) { if (scan < LAST_SCAN) goto continue_resched;