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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CCF96C388F7 for ; Tue, 3 Nov 2020 21:05:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D07520658 for ; Tue, 3 Nov 2020 21:05:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604437544; bh=+2rSuM/SGmBGFlt7/WiFPIMXBBRaJz7H9rWwAdJiOSo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=N1sVQDH99CMjHWw16AfeMdUsroJm/X8rRUJIzPypm31siPocveCClGK2tI7vfh7QY aD9Ymh+mqrJgeRuYht8hE81dGFVlPKzJEzrpl2APBA1X4BweJNjTco3C4MWDzWJuSB KDx8tUkfq6Xv4PbFqEaKquhpw/XbP/nHHM8AJYdw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388047AbgKCVFm (ORCPT ); Tue, 3 Nov 2020 16:05:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:44260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387867AbgKCVFi (ORCPT ); Tue, 3 Nov 2020 16:05:38 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4FB7122403; Tue, 3 Nov 2020 21:05:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604437537; bh=+2rSuM/SGmBGFlt7/WiFPIMXBBRaJz7H9rWwAdJiOSo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jp45s3hrxidaa6oh3RZXdrII4GuH8yJbA0B4Ff85MAS8hFs9UMSmMNCFIlYngKe5j K5ujsU+g7EIP6gpMv2MPhEqmLBaQfQ0GCG2qdlGzQ4dF7po6fX3qCYyKToaCUzVIZY CgWFcubUE24xInsvFFsWlQbuw6rGXsjOsuBdadsQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ye Bin , Jan Kara , Christoph Hellwig , Jens Axboe Subject: [PATCH 4.19 118/191] fs: Dont invalidate page buffers in block_write_full_page() Date: Tue, 3 Nov 2020 21:36:50 +0100 Message-Id: <20201103203244.395380058@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201103203232.656475008@linuxfoundation.org> References: <20201103203232.656475008@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: Jan Kara commit 6dbf7bb555981fb5faf7b691e8f6169fc2b2e63b upstream. If block_write_full_page() is called for a page that is beyond current inode size, it will truncate page buffers for the page and return 0. This logic has been added in 2.5.62 in commit 81eb69062588 ("fix ext3 BUG due to race with truncate") in history.git tree to fix a problem with ext3 in data=ordered mode. This particular problem doesn't exist anymore because ext3 is long gone and ext4 handles ordered data differently. Also normally buffers are invalidated by truncate code and there's no need to specially handle this in ->writepage() code. This invalidation of page buffers in block_write_full_page() is causing issues to filesystems (e.g. ext4 or ocfs2) when block device is shrunk under filesystem's hands and metadata buffers get discarded while being tracked by the journalling layer. Although it is obviously "not supported" it can cause kernel crashes like: [ 7986.689400] BUG: unable to handle kernel NULL pointer dereference at +0000000000000008 [ 7986.697197] PGD 0 P4D 0 [ 7986.699724] Oops: 0002 [#1] SMP PTI [ 7986.703200] CPU: 4 PID: 203778 Comm: jbd2/dm-3-8 Kdump: loaded Tainted: G +O --------- - - 4.18.0-147.5.0.5.h126.eulerosv2r9.x86_64 #1 [ 7986.716438] Hardware name: Huawei RH2288H V3/BC11HGSA0, BIOS 1.57 08/11/2015 [ 7986.723462] RIP: 0010:jbd2_journal_grab_journal_head+0x1b/0x40 [jbd2] ... [ 7986.810150] Call Trace: [ 7986.812595] __jbd2_journal_insert_checkpoint+0x23/0x70 [jbd2] [ 7986.818408] jbd2_journal_commit_transaction+0x155f/0x1b60 [jbd2] [ 7986.836467] kjournald2+0xbd/0x270 [jbd2] which is not great. The crash happens because bh->b_private is suddently NULL although BH_JBD flag is still set (this is because block_invalidatepage() cleared BH_Mapped flag and subsequent bh lookup found buffer without BH_Mapped set, called init_page_buffers() which has rewritten bh->b_private). So just remove the invalidation in block_write_full_page(). Note that the buffer cache invalidation when block device changes size is already careful to avoid similar problems by using invalidate_mapping_pages() which skips busy buffers so it was only this odd block_write_full_page() behavior that could tear down bdev buffers under filesystem's hands. Reported-by: Ye Bin Signed-off-by: Jan Kara Reviewed-by: Christoph Hellwig CC: stable@vger.kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- fs/buffer.c | 16 ---------------- 1 file changed, 16 deletions(-) --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2742,16 +2742,6 @@ int nobh_writepage(struct page *page, ge /* Is the page fully outside i_size? (truncate in progress) */ offset = i_size & (PAGE_SIZE-1); if (page->index >= end_index+1 || !offset) { - /* - * The page may have dirty, unmapped buffers. For example, - * they may have been added in ext3_writepage(). Make them - * freeable here, so the page does not leak. - */ -#if 0 - /* Not really sure about this - do we need this ? */ - if (page->mapping->a_ops->invalidatepage) - page->mapping->a_ops->invalidatepage(page, offset); -#endif unlock_page(page); return 0; /* don't care */ } @@ -2946,12 +2936,6 @@ int block_write_full_page(struct page *p /* Is the page fully outside i_size? (truncate in progress) */ offset = i_size & (PAGE_SIZE-1); if (page->index >= end_index+1 || !offset) { - /* - * The page may have dirty, unmapped buffers. For example, - * they may have been added in ext3_writepage(). Make them - * freeable here, so the page does not leak. - */ - do_invalidatepage(page, 0, PAGE_SIZE); unlock_page(page); return 0; /* don't care */ }