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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 36358C1975A for ; Thu, 12 Mar 2020 17:02:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0BD59206FA for ; Thu, 12 Mar 2020 17:02:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584032565; bh=pndlQWVpIlLEdq0CoJbaFOBobZ6FpPGHFPTz1MosdZU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=DlfGlZyEN/7D7rDk/Rhekmp51qpfcDFSD1bzksWYvV64gMKErmygGQ52aPc0pCDsf 77Z/UJWWbMRIJ3I/XpSnUuoGcdWLO5liHID2rtmMm7rd/oCoQ5yct9gkWHtVBqNO4L 2uNHzmy/FcbYeirYTj535+Zt7sLs32p/F35Vybpc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726406AbgCLRCo (ORCPT ); Thu, 12 Mar 2020 13:02:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:46516 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725268AbgCLRCn (ORCPT ); Thu, 12 Mar 2020 13:02:43 -0400 Received: from localhost (unknown [104.132.1.66]) (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 3AE04206F1; Thu, 12 Mar 2020 17:02:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584032563; bh=pndlQWVpIlLEdq0CoJbaFOBobZ6FpPGHFPTz1MosdZU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nKVh5mylNYTKPgikOSPbui2uAmArPeg2ln5wJCnpsrgCimianVTyWWafCL+7++LW6 D9JVo1VhQuPDa4WryDdbeIO9A/YHQ2dRKr5t4SfW5JvCTtuPg+S4oL9+Dz0sQmsXwz 24jToMCjb1trH+n6ANf75NyyS5Gx//EcgT6CtyAg= Date: Thu, 12 Mar 2020 10:02:42 -0700 From: Jaegeuk Kim To: Sahitya Tummala Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] f2fs: fix long latency due to discard during umount Message-ID: <20200312170242.GA185506@google.com> References: <1584011671-20939-1-git-send-email-stummala@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1584011671-20939-1-git-send-email-stummala@codeaurora.org> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/12, 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 > --- > fs/f2fs/segment.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index fb3e531..a06bbac 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -1124,10 +1124,13 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, > struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info; > struct list_head *wait_list = (dpolicy->type == DPOLICY_FSTRIM) ? > &(dcc->fstrim_list) : &(dcc->wait_list); > - int flag = dpolicy->sync ? REQ_SYNC : 0; > + int flag; > block_t lstart, start, len, total_len; > int err = 0; > > + flag = dpolicy->sync ? REQ_SYNC : 0; > + flag |= dpolicy->type == DPOLICY_UMOUNT ? REQ_NOWAIT : 0; > + > if (dc->state != D_PREP) > return 0; > > @@ -1203,6 +1206,11 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, > bio->bi_end_io = f2fs_submit_discard_endio; > bio->bi_opf |= flag; > submit_bio(bio); > + if ((flag & REQ_NOWAIT) && (dc->error == -EAGAIN)) { > + dc->state = D_PREP; > + err = dc->error; > + break; > + } > > atomic_inc(&dcc->issued_discard); > > @@ -1510,6 +1518,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > } > > __submit_discard_cmd(sbi, dpolicy, dc, &issued); > + if (dc->error == -EAGAIN) { > + congestion_wait(BLK_RW_ASYNC, HZ/50); --> need to be DEFAULT_IO_TIMEOUT > + __relocate_discard_cmd(dcc, dc); It seems we need to submit bio first, and then move dc to wait_list, if there's no error, in __submit_discard_cmd(). > + } > > if (issued >= dpolicy->max_requests) > break; > -- > Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.