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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 9F77EC433DB for ; Tue, 16 Mar 2021 10:31:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4CA6265027 for ; Tue, 16 Mar 2021 10:31:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236488AbhCPKa2 (ORCPT ); Tue, 16 Mar 2021 06:30:28 -0400 Received: from mail.synology.com ([211.23.38.101]:42972 "EHLO synology.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S236569AbhCPKaD (ORCPT ); Tue, 16 Mar 2021 06:30:03 -0400 Subject: Re: [PATCH v2] block: fix trace completion for chained bio DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=synology.com; s=123; t=1615890602; bh=bytYvWpMK+2SPyQATrsWUcRSbI+iXR9EQhuampwSLxg=; h=Subject:To:Cc:References:From:Date:In-Reply-To; b=TDFAuZZgIuiLzfDJ5Ze+NAIN7OP/LFyPxwAenzNa9HeznkyuZXIaatG4yTH5JwWE1 inPFb+5FlSHQE0UEXM60WldeycIKAAjtS2KoxnkrKOFy42X0M7atVjQ5F8Smx8BRRK bhojU3M4XHLtcHZZ+XWAmU/K9HyzrbSIBy3H6rmc= To: axboe@kernel.dk, neilb@suse.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, s3t@synology.com, bingjingc@synology.com, cccheng@synology.com References: <1614741726-28074-1-git-send-email-edwardh@synology.com> From: Edward Hsieh Message-ID: Date: Tue, 16 Mar 2021 18:30:02 +0800 MIME-Version: 1.0 In-Reply-To: <1614741726-28074-1-git-send-email-edwardh@synology.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Synology-MCP-Status: no X-Synology-Spam-Flag: no X-Synology-Spam-Status: score=0, required 6, WHITELIST_FROM_ADDRESS 0 X-Synology-Virus-Status: no Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Jens and Neil, Is there any feedback on this patch? Thank you, Edward Hsieh On 3/3/2021 11:22 AM, Edward Hsieh wrote: > From: Edward Hsieh > > For chained bio, trace_block_bio_complete in bio_endio is currently called > only by the parent bio once upon all chained bio completed. > However, the sector and size for the parent bio are modified in bio_split. > Therefore, the size and sector of the complete events might not match the > queue events in blktrace. > > The original fix of bio completion trace ("block: trace > completion of all bios.") wants multiple complete events to correspond > to one queue event but missed this. > > md/raid5 read with bio cross chunks can reproduce this issue. > > To fix, move trace completion into the loop for every chained bio to call. > > Fixes: fbbaf700e7b1 ("block: trace completion of all bios.") > Reviewed-by: Wade Liang > Reviewed-by: BingJing Chang > Signed-off-by: Edward Hsieh > --- > block/bio.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index a1c4d29..2ff72cb 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -1397,8 +1397,7 @@ static inline bool bio_remaining_done(struct bio *bio) > * > * bio_endio() can be called several times on a bio that has been chained > * using bio_chain(). The ->bi_end_io() function will only be called the > - * last time. At this point the BLK_TA_COMPLETE tracing event will be > - * generated if BIO_TRACE_COMPLETION is set. > + * last time. > **/ > void bio_endio(struct bio *bio) > { > @@ -1411,6 +1410,11 @@ void bio_endio(struct bio *bio) > if (bio->bi_bdev) > rq_qos_done_bio(bio->bi_bdev->bd_disk->queue, bio); > > + if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) { > + trace_block_bio_complete(bio->bi_bdev->bd_disk->queue, bio); > + bio_clear_flag(bio, BIO_TRACE_COMPLETION); > + } > + > /* > * Need to have a real endio function for chained bios, otherwise > * various corner cases will break (like stacking block devices that > @@ -1424,11 +1428,6 @@ void bio_endio(struct bio *bio) > goto again; > } > > - if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) { > - trace_block_bio_complete(bio->bi_bdev->bd_disk->queue, bio); > - bio_clear_flag(bio, BIO_TRACE_COMPLETION); > - } > - > blk_throtl_bio_endio(bio); > /* release cgroup info */ > bio_uninit(bio); >