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 75437C2BB1D for ; Fri, 13 Mar 2020 15:38:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E513206E2 for ; Fri, 13 Mar 2020 15:38:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584113930; bh=SRcprPq3VbUw28EYa7ZTMQ0PDgqkWwXJE4sUUr+6mak=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=vpvIjLSSfO2VFgpcurkdWWeCFQQBKmGbCebyJUWn5PT+QSCuniGRd1EqcuFpjyAT9 4/P4qZIZjyDwQ60adleEcA9uZ5PUTnVKpNfn1UpcCxV09A8E/3SmarHaOIcRkcHQG/ jSPfjTOsI6zNZVe8jZaWDoqJWCUwtkrvtyyqEt4s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726684AbgCMPit (ORCPT ); Fri, 13 Mar 2020 11:38:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:46084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726420AbgCMPis (ORCPT ); Fri, 13 Mar 2020 11:38:48 -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 C6F1E206B7; Fri, 13 Mar 2020 15:38:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584113927; bh=SRcprPq3VbUw28EYa7ZTMQ0PDgqkWwXJE4sUUr+6mak=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AK9IQ7fafeWpV/b8ZdLGtNbLAeXPqMoyNVnWkSl9ctJv6P00D6o7eDydetcG5jnNQ KaXRui8AwelxVhb8R1mU5D6RGmQEi9FsaUjNr1v/T50U9Qsmmc2iVveRVq6TCCNqUa ygaJLjogAYUY+6cKRK9vhCCUiZJyvYjOfI9ZRV4c= Date: Fri, 13 Mar 2020 08:38:47 -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: <20200313153847.GA185439@google.com> References: <1584011671-20939-1-git-send-email-stummala@codeaurora.org> <20200312170242.GA185506@google.com> <20200313012604.GI20234@codeaurora.org> <20200313014535.GA72547@google.com> <20200313051245.GK20234@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200313051245.GK20234@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 03/13, Sahitya Tummala wrote: > On Thu, Mar 12, 2020 at 06:45:35PM -0700, Jaegeuk Kim wrote: > > On 03/13, Sahitya Tummala wrote: > > > On Thu, Mar 12, 2020 at 10:02:42AM -0700, Jaegeuk Kim wrote: > > > > 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 > > > > > > Yes, i will update it. > > > > > > > > > > > > + __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(). > > > > > > Yes, that is not changed and it still happens for the failed request > > > that is re-queued here too when it gets submitted again later. > > > > > > I am requeuing the discard request failed with -EAGAIN error back to > > > dcc->pend_list[] from wait_list. It will call submit_bio() for this request > > > and also move to wait_list when it calls __submit_discard_cmd() again next > > > time. Please let me know if I am missing anything? > > > > This patch has no problem, but I'm thinking that __submit_discard_cmd() needs > > to return with any values by assumption where the waiting list should have > > submitted commands. > > I think dc->queued will indicated that dc is moved to wait_list. This can be > used along with return value to take right action. Can you check if this > works? I mean why can't do this *in* __submit_discard_cmd()? Otherwise, existing and future callers should consider to handle the errors everytime. > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index a06bbac..91df060 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -1478,7 +1478,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > struct list_head *pend_list; > struct discard_cmd *dc, *tmp; > struct blk_plug plug; > - int i, issued = 0; > + int i, err, issued = 0; > bool io_interrupted = false; > > if (dpolicy->timeout != 0) > @@ -1517,8 +1517,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > break; > } > > - __submit_discard_cmd(sbi, dpolicy, dc, &issued); > - if (dc->error == -EAGAIN) { > + err = __submit_discard_cmd(sbi, dpolicy, dc, &issued); > + if (err && err != -EAGAIN) { > + __remove_discard_cmd(sbi, dc); > + } else if (err == -EAGAIN && dc->queued) { > congestion_wait(BLK_RW_ASYNC, HZ/50); > __relocate_discard_cmd(dcc, dc); > } > > thanks, > > > > > > > > Thanks, > > > > > > > > > > > > + } > > > > > > > > > > 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. > > > > > > -- > > > -- > > > Sent by a consultant of the Qualcomm Innovation Center, Inc. > > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. > > -- > -- > Sent by a consultant of the Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.