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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 177A9C3A5A0 for ; Mon, 20 Apr 2020 12:43:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC60A2072B for ; Mon, 20 Apr 2020 12:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587386616; bh=61WFqwITioEntxRH6QDaMEwXKdxo0S5pX28b3CWeGdc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0KhonfIxN+TdU14X1McOeg6oElG8SxQXtR3Z5zv4Sx+HRamdectH0Sv3UqyVI2DTw 7/K5xHgjD+kfdS+/VZ8s9E1xo6wG/MmT83Hv6RSkO5/KZOhuaEJkebfjUFwGb73zxs hvLEwqRWkb0QxiLfcOdJbQ3fUVVF7sQLms9bJCJA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728415AbgDTMnf (ORCPT ); Mon, 20 Apr 2020 08:43:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:37058 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728395AbgDTMn2 (ORCPT ); Mon, 20 Apr 2020 08:43:28 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 8FA3220735; Mon, 20 Apr 2020 12:43:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587386608; bh=61WFqwITioEntxRH6QDaMEwXKdxo0S5pX28b3CWeGdc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hbB2B8kcJbd8HxzRnWiUV9qm2/nvEBBUcuPTl62TUGGXgluE2kUQqMx14oaXIqfdC HzKqNe9pC8emftAHBONmW2ki+pR6nqXJZsu1IwzPZimMtCB1GxsHr8Cw6HGLiT8Lzh wbyDm2KROrxPQSenDrTJIACmJYDJhu4fAwXuL7hk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kara , "zhangyi (F)" , Theodore Tso Subject: [PATCH 5.6 26/71] jbd2: improve comments about freeing data buffers whose page mapping is NULL Date: Mon, 20 Apr 2020 14:38:40 +0200 Message-Id: <20200420121513.759932086@linuxfoundation.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200420121508.491252919@linuxfoundation.org> References: <20200420121508.491252919@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: zhangyi (F) commit 780f66e59231fcf882f36c63f287252ee47cc75a upstream. Improve comments in jbd2_journal_commit_transaction() to describe why we don't need to clear the buffer_mapped bit for freeing file mapping buffers whose page mapping is NULL. Link: https://lore.kernel.org/r/20200217112706.20085-1-yi.zhang@huawei.com Fixes: c96dceeabf76 ("jbd2: do not clear the BH_Mapped flag when forgetting a metadata buffer") Suggested-by: Jan Kara Reviewed-by: Jan Kara Signed-off-by: zhangyi (F) Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/jbd2/commit.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -997,9 +997,10 @@ restart_loop: * journalled data) we need to unmap buffer and clear * more bits. We also need to be careful about the check * because the data page mapping can get cleared under - * out hands, which alse need not to clear more bits - * because the page and buffers will be freed and can - * never be reused once we are done with them. + * our hands. Note that if mapping == NULL, we don't + * need to make buffer unmapped because the page is + * already detached from the mapping and buffers cannot + * get reused. */ mapping = READ_ONCE(bh->b_page->mapping); if (mapping && !sb_is_blkdev_sb(mapping->host->i_sb)) {