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 04772C55186 for ; Wed, 22 Apr 2020 10:05:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C54DF20857 for ; Wed, 22 Apr 2020 10:05:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587549952; bh=XK9eMSM/yxlwNs6spFUXAH1CLJpeXLHJC3qRUonC59c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=be5wHKHcjZa1XembSfX8BPuKtq32kpW6673Wld8VeyK/lr0HuH5s1P2RPPxl9zu9F AAA0RIPsIJJWuuVsr6f+5ir5MpIMIaYbCWadNnK6BE98VH44l46JOxDwZjUqgPVRy6 HZjUOGhNW0s4AeX52Kpln7kSkDbko6n+otB1NFtU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728242AbgDVKFw (ORCPT ); Wed, 22 Apr 2020 06:05:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:57168 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728225AbgDVKFq (ORCPT ); Wed, 22 Apr 2020 06:05:46 -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 E71C42075A; Wed, 22 Apr 2020 10:05:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587549945; bh=XK9eMSM/yxlwNs6spFUXAH1CLJpeXLHJC3qRUonC59c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w7ENCVFuq3fetWKESrlZAl+kE24dQK8AFaT3tl0bU3qzKq90FWWL3cIBOvTzKkzIx LusbvnyiVJfNXEbIi0IlSdIC8r/HC4saTp6XPCrJ+THrvHB1JJfT95DBFHS0EpQAd7 cgoQpBmX9nnnBppN+sX6y/LIO3lP17iSyI3DN1/Q= 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 4.9 071/125] jbd2: improve comments about freeing data buffers whose page mapping is NULL Date: Wed, 22 Apr 2020 11:56:28 +0200 Message-Id: <20200422095044.766641370@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200422095032.909124119@linuxfoundation.org> References: <20200422095032.909124119@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 @@ -990,9 +990,10 @@ 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)) {