From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B7B9F233733 for ; Mon, 24 Feb 2025 12:54:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740401643; cv=none; b=sgZvGhhZ2odEo5zdrhnqOJz31grqxMYhv/lyL9zqA1ccb721rN3aa74VyjSmKCRxAooaw0aJHfnQhRVEbQSazzsBaMjiakbFnkHIFO3m3KGWtKj/E/kMgrm167CrNb3wv5mNI4ufHS9FzOVR5Sk1qoD9Ptkn5q8oaOqRhsEJgCw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740401643; c=relaxed/simple; bh=cPqFlN9hhPH5PUCieVKmof6OSDpqARoal3nq00GKLP0=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=B/22OiNRfBUtaPA0hehwMErkswQacT9bT9DgCdWPCdzyFUkxCHsCKCIAK2rdulC7Vs9pRhAqun3oT6OgyuVMM75MpV0CFWYXS7T+uJN7m2r682GZkOjAXJfVHRu0y5omgEpVP8v/ZDQYD9C3Ad6Y3/62mxHTEm0cKWV4Bn7PnqI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=W/Air6NL; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="W/Air6NL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740401640; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=RyZKAT7kvX4bnRDx3j7DvsDLJEcrsNoetXZGX7kmB2s=; b=W/Air6NLEPAuApYZjjaVIqfGZDnqZ0aCB3J+idrH47XqdkRLcjvcGOmR4Su3VQEszNUQo4 gd/CB7HWDCNIWRjZdeqzbmDab9Mf7sG5tKH9ZTXYQE6kxG+v4bOJBpyhyNNLS78reHemA2 9uoUvrWO6Mttfca79XpQx649t57l+aY= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-650-sr5YoVDqONGmoayMPwNkzw-1; Mon, 24 Feb 2025 07:53:56 -0500 X-MC-Unique: sr5YoVDqONGmoayMPwNkzw-1 X-Mimecast-MFC-AGG-ID: sr5YoVDqONGmoayMPwNkzw_1740401634 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E23A51800874; Mon, 24 Feb 2025 12:53:53 +0000 (UTC) Received: from [10.45.224.44] (unknown [10.45.224.44]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A1C9D300018D; Mon, 24 Feb 2025 12:53:50 +0000 (UTC) Date: Mon, 24 Feb 2025 13:53:47 +0100 (CET) From: Mikulas Patocka To: Jinliang Zheng cc: agk@redhat.com, snitzer@kernel.org, dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, flyingpeng@tencent.com, txpeng@tencent.com, dchinner@redhat.com, Jinliang Zheng Subject: Re: [PATCH] dm: fix unconditional IO throttle caused by REQ_PREFLUSH In-Reply-To: <20250220112014.3209940-1-alexjlzheng@tencent.com> Message-ID: <1931a9db-a81d-daf2-2e89-d1f183946618@redhat.com> References: <20250220112014.3209940-1-alexjlzheng@tencent.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Applied, thanks. Mikulas On Thu, 20 Feb 2025, Jinliang Zheng wrote: > When a bio with REQ_PREFLUSH is submitted to dm, __send_empty_flush() > generates a flush_bio with REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC, > which causes the flush_bio to be throttled by wbt_wait(). > > An example from v5.4, similar problem also exists in upstream: > > crash> bt 2091206 > PID: 2091206 TASK: ffff2050df92a300 CPU: 109 COMMAND: "kworker/u260:0" > #0 [ffff800084a2f7f0] __switch_to at ffff80004008aeb8 > #1 [ffff800084a2f820] __schedule at ffff800040bfa0c4 > #2 [ffff800084a2f880] schedule at ffff800040bfa4b4 > #3 [ffff800084a2f8a0] io_schedule at ffff800040bfa9c4 > #4 [ffff800084a2f8c0] rq_qos_wait at ffff8000405925bc > #5 [ffff800084a2f940] wbt_wait at ffff8000405bb3a0 > #6 [ffff800084a2f9a0] __rq_qos_throttle at ffff800040592254 > #7 [ffff800084a2f9c0] blk_mq_make_request at ffff80004057cf38 > #8 [ffff800084a2fa60] generic_make_request at ffff800040570138 > #9 [ffff800084a2fae0] submit_bio at ffff8000405703b4 > #10 [ffff800084a2fb50] xlog_write_iclog at ffff800001280834 [xfs] > #11 [ffff800084a2fbb0] xlog_sync at ffff800001280c3c [xfs] > #12 [ffff800084a2fbf0] xlog_state_release_iclog at ffff800001280df4 [xfs] > #13 [ffff800084a2fc10] xlog_write at ffff80000128203c [xfs] > #14 [ffff800084a2fcd0] xlog_cil_push at ffff8000012846dc [xfs] > #15 [ffff800084a2fda0] xlog_cil_push_work at ffff800001284a2c [xfs] > #16 [ffff800084a2fdb0] process_one_work at ffff800040111d08 > #17 [ffff800084a2fe00] worker_thread at ffff8000401121cc > #18 [ffff800084a2fe70] kthread at ffff800040118de4 > > After commit 2def2845cc33 ("xfs: don't allow log IO to be throttled"), > the metadata submitted by xlog_write_iclog() should not be throttled. > But due to the existence of the dm layer, throttling flush_bio indirectly > causes the metadata bio to be throttled. > > Fix this by conditionally adding REQ_IDLE to flush_bio.bi_opf, which makes > wbt_should_throttle() return false to avoid wbt_wait(). > > Signed-off-by: Jinliang Zheng > Reviewed-by: Tianxiang Peng > Reviewed-by: Hao Peng > --- > drivers/md/dm.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > index 4d1e42891d24..5ab7574c0c76 100644 > --- a/drivers/md/dm.c > +++ b/drivers/md/dm.c > @@ -1540,14 +1540,18 @@ static void __send_empty_flush(struct clone_info *ci) > { > struct dm_table *t = ci->map; > struct bio flush_bio; > + blk_opf_t opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC; > + > + if ((ci->io->orig_bio->bi_opf & (REQ_IDLE | REQ_SYNC)) == > + (REQ_IDLE | REQ_SYNC)) > + opf |= REQ_IDLE; > > /* > * Use an on-stack bio for this, it's safe since we don't > * need to reference it after submit. It's just used as > * the basis for the clone(s). > */ > - bio_init(&flush_bio, ci->io->md->disk->part0, NULL, 0, > - REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC); > + bio_init(&flush_bio, ci->io->md->disk->part0, NULL, 0, opf); > > ci->bio = &flush_bio; > ci->sector_count = 0; > -- > 2.41.1 >