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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 BF20EC10DCE for ; Fri, 13 Mar 2020 03:39:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F7DA206CD for ; Fri, 13 Mar 2020 03:39:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="BQ2MAY7/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726446AbgCMDj2 (ORCPT ); Thu, 12 Mar 2020 23:39:28 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:41370 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726254AbgCMDj1 (ORCPT ); Thu, 12 Mar 2020 23:39:27 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1584070767; h=In-Reply-To: Content-Type: MIME-Version: References: Message-ID: Subject: Cc: To: From: Date: Sender; bh=SLp1RSSJXXFi0aM9dH+otJ/jiCUrThG79PUgGB7bTWM=; b=BQ2MAY7/bsRVeZq2I7P9xmyQxQBpu4ygotX1Ugu379hR6f/Y87VAC9usfSoO3G73mCsjiCCa VRjN7v5fBQgt0r9ydXI6iIPdZ5uOGUWztXK0l74GbdtWmULrYQJXtzw6w98jz0GcN3+Sldfo Si+huZr8TVe0LngkXlGFOOYFukA= X-Mailgun-Sending-Ip: 104.130.122.26 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5e6b0066.7f0d0537d688-smtp-out-n01; Fri, 13 Mar 2020 03:39:18 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 7B5ECC433CB; Fri, 13 Mar 2020 03:39:18 +0000 (UTC) Received: from codeaurora.org (blr-c-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: stummala) by smtp.codeaurora.org (Postfix) with ESMTPSA id 2D33FC433BA; Fri, 13 Mar 2020 03:39:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 2D33FC433BA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=stummala@codeaurora.org Date: Fri, 13 Mar 2020 09:09:12 +0530 From: Sahitya Tummala To: Chao Yu Cc: Jaegeuk Kim , 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: <20200313033912.GJ20234@codeaurora.org> 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: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 13, 2020 at 10:20:04AM +0800, Chao Yu wrote: > On 2020/3/12 19:14, 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)) { > > If we want to update dc->state, we need to cover it with dc->lock. Sure, will update it. > > > + dc->state = D_PREP; > > BTW, one dc can be referenced by multiple bios, so dc->state could be updated to > D_DONE later by f2fs_submit_discard_endio(), however we just relocate it to > pending list... which is inconsistent status. In that case dc->bio_ref will reflect it and until it becomes 0, the dc->state will not be updated to D_DONE in f2fs_submit_discard_endio()? Thanks, > > Thanks, > > > + 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); > > + __relocate_discard_cmd(dcc, dc); > > + } > > > > if (issued >= dpolicy->max_requests) > > break; > > -- -- Sent by a consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.