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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 91E22C4332B for ; Tue, 24 Mar 2020 09:09:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67FEB205ED for ; Tue, 24 Mar 2020 09:09:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727209AbgCXJJD (ORCPT ); Tue, 24 Mar 2020 05:09:03 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:12185 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726845AbgCXJJD (ORCPT ); Tue, 24 Mar 2020 05:09:03 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 91A9F400B6F2CCFD201C; Tue, 24 Mar 2020 17:09:00 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.213) with Microsoft SMTP Server (TLS) id 14.3.487.0; Tue, 24 Mar 2020 17:08:58 +0800 Subject: Re: [PATCH] f2fs: fix long latency due to discard during umount To: Sahitya Tummala , Jaegeuk Kim , CC: References: <1584506689-5041-1-git-send-email-stummala@codeaurora.org> From: Chao Yu Message-ID: <54ae330b-ac9b-7968-fa0a-95db6737e3ea@huawei.com> Date: Tue, 24 Mar 2020 17:08:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1584506689-5041-1-git-send-email-stummala@codeaurora.org> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/3/18 12:44, Sahitya Tummala wrote: > F2FS already has a default timeout of 5 secs for discards that > can be issued during umount, but it can take more than the 5 sec > timeout if the underlying UFS device queue is already full and there > are no more available free tags to be used. In that case, submit_bio() > will wait for the already queued discard requests to complete to get > a free tag, which can potentially take way more than 5 sec. > > Fix this by submitting the discard requests with REQ_NOWAIT > flags during umount. This will return -EAGAIN for UFS queue/tag full > scenario without waiting in the context of submit_bio(). The FS can > then handle these requests by retrying again within the stipulated > discard timeout period to avoid long latencies. > > Signed-off-by: Sahitya Tummala Reviewed-by: Chao Yu Thanks,