From nobody Fri Sep 19 05:51:02 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76680C4332F for ; Tue, 29 Nov 2022 03:02:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235382AbiK2DCX (ORCPT ); Mon, 28 Nov 2022 22:02:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235301AbiK2DB4 (ORCPT ); Mon, 28 Nov 2022 22:01:56 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB3CD45EF1; Mon, 28 Nov 2022 19:01:54 -0800 (PST) Received: from kwepemi500016.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4NLnCq49DWzCqjJ; Tue, 29 Nov 2022 11:01:11 +0800 (CST) Received: from huawei.com (10.174.178.129) by kwepemi500016.china.huawei.com (7.221.188.220) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 29 Nov 2022 11:01:52 +0800 From: Kemeng Shi To: , , CC: , , , Subject: [PATCH v2 04/10] blk-throttle: correct calculation of wait time in tg_may_dispatch Date: Tue, 29 Nov 2022 11:01:41 +0800 Message-ID: <20221129030147.27400-5-shikemeng@huawei.com> X-Mailer: git-send-email 2.14.1.windows.1 In-Reply-To: <20221129030147.27400-1-shikemeng@huawei.com> References: <20221129030147.27400-1-shikemeng@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.129] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemi500016.china.huawei.com (7.221.188.220) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In C language, When executing "if (expression1 && expression2)" and expression1 return false, the expression2 may not be executed. For "tg_within_bps_limit(tg, bio, bps_limit, &bps_wait) && tg_within_iops_limit(tg, bio, iops_limit, &iops_wait))", if bps is limited, tg_within_bps_limit will return false and tg_within_iops_limit will not be called. So even bps and iops are both limited, iops_wait will not be calculated and is always zero. So wait time of iops is always ignored. Fix this by always calling tg_within_bps_limit and tg_within_iops_limit to get wait time for both bps and iops. Observed that: 1. Wait time in tg_within_iops_limit/tg_within_bps_limit need always be stored as wait argument is always passed. 2. wait time is stored to zero if iops/bps is limited otherwise non-zero is stored. Simpfy tg_within_iops_limit/tg_within_bps_limit by removing wait argument and return wait time directly. Caller tg_may_dispatch checks if wait time is zero to find if iops/bps is limited. Signed-off-by: Kemeng Shi Acked-by: Tejun Heo --- block/blk-throttle.c | 38 +++++++++++++------------------------- 1 file changed, 13 insertions(+), 25 deletions(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index ee7dc1a0adfd..06e4193b064e 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -822,17 +822,15 @@ static void tg_update_carryover(struct throtl_grp *tg) tg->carryover_ios[READ], tg->carryover_ios[WRITE]); } =20 -static bool tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio, - u32 iops_limit, unsigned long *wait) +static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bi= o *bio, + u32 iops_limit) { bool rw =3D bio_data_dir(bio); unsigned int io_allowed; unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; =20 if (iops_limit =3D=3D UINT_MAX) { - if (wait) - *wait =3D 0; - return true; + return 0; } =20 jiffy_elapsed =3D jiffies - tg->slice_start[rw]; @@ -842,21 +840,16 @@ static bool tg_within_iops_limit(struct throtl_grp *t= g, struct bio *bio, io_allowed =3D calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) + tg->carryover_ios[rw]; if (tg->io_disp[rw] + 1 <=3D io_allowed) { - if (wait) - *wait =3D 0; - return true; + return 0; } =20 /* Calc approx time to dispatch */ jiffy_wait =3D jiffy_elapsed_rnd - jiffy_elapsed; - - if (wait) - *wait =3D jiffy_wait; - return false; + return jiffy_wait; } =20 -static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, - u64 bps_limit, unsigned long *wait) +static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio= *bio, + u64 bps_limit) { bool rw =3D bio_data_dir(bio); u64 bytes_allowed, extra_bytes; @@ -865,9 +858,7 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, = struct bio *bio, =20 /* no need to throttle if this bio's bytes have been accounted */ if (bps_limit =3D=3D U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) { - if (wait) - *wait =3D 0; - return true; + return 0; } =20 jiffy_elapsed =3D jiffy_elapsed_rnd =3D jiffies - tg->slice_start[rw]; @@ -880,9 +871,7 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, = struct bio *bio, bytes_allowed =3D calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) + tg->carryover_bytes[rw]; if (tg->bytes_disp[rw] + bio_size <=3D bytes_allowed) { - if (wait) - *wait =3D 0; - return true; + return 0; } =20 /* Calc approx time to dispatch */ @@ -897,9 +886,7 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, = struct bio *bio, * up we did. Add that time also. */ jiffy_wait =3D jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); - if (wait) - *wait =3D jiffy_wait; - return false; + return jiffy_wait; } =20 /* @@ -947,8 +934,9 @@ static bool tg_may_dispatch(struct throtl_grp *tg, stru= ct bio *bio, jiffies + tg->td->throtl_slice); } =20 - if (tg_within_bps_limit(tg, bio, bps_limit, &bps_wait) && - tg_within_iops_limit(tg, bio, iops_limit, &iops_wait)) { + bps_wait =3D tg_within_bps_limit(tg, bio, bps_limit); + iops_wait =3D tg_within_iops_limit(tg, bio, iops_limit); + if (bps_wait + iops_wait =3D=3D 0) { if (wait) *wait =3D 0; return true; --=20 2.30.0