From patchwork Mon Feb 17 11:27:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhang Yi X-Patchwork-Id: 1239139 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=huawei.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48LhZ00sp3z9sNg for ; Mon, 17 Feb 2020 22:28:23 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728130AbgBQL2X (ORCPT ); Mon, 17 Feb 2020 06:28:23 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:52642 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726558AbgBQL2X (ORCPT ); Mon, 17 Feb 2020 06:28:23 -0500 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 50FA7E43C055C908BD9B; Mon, 17 Feb 2020 19:28:20 +0800 (CST) Received: from huawei.com (10.175.124.28) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.439.0; Mon, 17 Feb 2020 19:28:13 +0800 From: "zhangyi (F)" To: CC: , , Subject: [PATCH] jbd2: improve comments about freeing data buffers whose page mapping is NULL Date: Mon, 17 Feb 2020 19:27:06 +0800 Message-ID: <20200217112706.20085-1-yi.zhang@huawei.com> X-Mailer: git-send-email 2.17.2 MIME-Version: 1.0 X-Originating-IP: [10.175.124.28] X-CFilter-Loop: Reflected Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org 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. Fixes: c96dceeabf76 ("jbd2: do not clear the BH_Mapped flag when forgetting a metadata buffer") Signed-off-by: zhangyi (F) Suggested-by: Jan Kara Reviewed-by: Jan Kara --- fs/jbd2/commit.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index 27373f5792a4..e855d8260433 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -997,9 +997,10 @@ void jbd2_journal_commit_transaction(journal_t *journal) * 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)) {