From nobody Fri Dec 19 17:34:20 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 308F2C04A95 for ; Sat, 22 Oct 2022 08:08:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233052AbiJVIIR (ORCPT ); Sat, 22 Oct 2022 04:08:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232875AbiJVIEU (ORCPT ); Sat, 22 Oct 2022 04:04:20 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6238E2D2C24; Sat, 22 Oct 2022 00:51:46 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 3C22CB82E03; Sat, 22 Oct 2022 07:41:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97E50C433C1; Sat, 22 Oct 2022 07:41:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666424471; bh=tQocI4AX+Xkhb6aZXEHJleSRliEKDtndK6ghaeMogRU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c2Q00ifCBe8r1fbckqdPW6/ttlvnTDDN+YULJBhhIanTZKifGdQTySNIQEZ3iP92L qd8sP4SGWY2UFuBDcPOtydIqngABVkr7zqI9Z5Y2XrxQDnuV4/l8QSy9UXN+PJuznt 5ty/Og7rV25G0uLaDDo7moig0g6waZ0jVXlgknJs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yu Kuai , Tejun Heo , Jens Axboe Subject: [PATCH 5.19 158/717] blk-throttle: fix that io throttle can only work for single bio Date: Sat, 22 Oct 2022 09:20:37 +0200 Message-Id: <20221022072443.408341338@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221022072415.034382448@linuxfoundation.org> References: <20221022072415.034382448@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Yu Kuai commit 320fb0f91e55ba248d4bad106b408e59099cfa89 upstream. Test scripts: cd /sys/fs/cgroup/blkio/ echo "8:0 1024" > blkio.throttle.write_bps_device echo $$ > cgroup.procs dd if=3D/dev/zero of=3D/dev/sda bs=3D10k count=3D1 oflag=3Ddirect & dd if=3D/dev/zero of=3D/dev/sda bs=3D10k count=3D1 oflag=3Ddirect & Test result: 10240 bytes (10 kB, 10 KiB) copied, 10.0134 s, 1.0 kB/s 10240 bytes (10 kB, 10 KiB) copied, 10.0135 s, 1.0 kB/s The problem is that the second bio is finished after 10s instead of 20s. Root cause: 1) second bio will be flagged: __blk_throtl_bio while (true) { ... if (sq->nr_queued[rw]) -> some bio is throttled already break }; bio_set_flag(bio, BIO_THROTTLED); -> flag the bio 2) flagged bio will be dispatched without waiting: throtl_dispatch_tg tg_may_dispatch tg_with_in_bps_limit if (bps_limit =3D=3D U64_MAX || bio_flagged(bio, BIO_THROTTLED)) *wait =3D 0; -> wait time is zero return true; commit 9f5ede3c01f9 ("block: throttle split bio in case of iops limit") support to count split bios for iops limit, thus it adds flagged bio checking in tg_with_in_bps_limit() so that split bios will only count once for bps limit, however, it introduce a new problem that io throttle won't work if multiple bios are throttled. In order to fix the problem, handle iops/bps limit in different ways: 1) for iops limit, there is no flag to record if the bio is throttled, and iops is always applied. 2) for bps limit, original bio will be flagged with BIO_BPS_THROTTLED, and io throttle will ignore bio with the flag. Noted this patch also remove the code to set flag in __bio_clone(), it's introduced in commit 111be8839817 ("block-throttle: avoid double charge"), and author thinks split bio can be resubmited and throttled again, which is wrong because split bio will continue to dispatch from caller. Fixes: 9f5ede3c01f9 ("block: throttle split bio in case of iops limit") Cc: Signed-off-by: Yu Kuai Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20220829022240.3348319-2-yukuai1@huaweiclou= d.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/bio.c | 2 -- block/blk-throttle.c | 20 ++++++-------------- block/blk-throttle.h | 2 +- include/linux/bio.h | 2 +- include/linux/blk_types.h | 2 +- 5 files changed, 9 insertions(+), 19 deletions(-) --- a/block/bio.c +++ b/block/bio.c @@ -760,8 +760,6 @@ EXPORT_SYMBOL(bio_put); static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp) { bio_set_flag(bio, BIO_CLONED); - if (bio_flagged(bio_src, BIO_THROTTLED)) - bio_set_flag(bio, BIO_THROTTLED); bio->bi_ioprio =3D bio_src->bi_ioprio; bio->bi_iter =3D bio_src->bi_iter; =20 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -811,7 +811,7 @@ static bool tg_with_in_bps_limit(struct unsigned int bio_size =3D throtl_bio_data_size(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_THROTTLED)) { + if (bps_limit =3D=3D U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) { if (wait) *wait =3D 0; return true; @@ -921,22 +921,13 @@ static void throtl_charge_bio(struct thr unsigned int bio_size =3D throtl_bio_data_size(bio); =20 /* Charge the bio to the group */ - if (!bio_flagged(bio, BIO_THROTTLED)) { + if (!bio_flagged(bio, BIO_BPS_THROTTLED)) { tg->bytes_disp[rw] +=3D bio_size; tg->last_bytes_disp[rw] +=3D bio_size; } =20 tg->io_disp[rw]++; tg->last_io_disp[rw]++; - - /* - * BIO_THROTTLED is used to prevent the same bio to be throttled - * more than once as a throttled bio will go through blk-throtl the - * second time when it eventually gets issued. Set it when a bio - * is being charged to a tg. - */ - if (!bio_flagged(bio, BIO_THROTTLED)) - bio_set_flag(bio, BIO_THROTTLED); } =20 /** @@ -1026,6 +1017,7 @@ static void tg_dispatch_one_bio(struct t sq->nr_queued[rw]--; =20 throtl_charge_bio(tg, bio); + bio_set_flag(bio, BIO_BPS_THROTTLED); =20 /* * If our parent is another tg, we just need to transfer @bio to @@ -2159,8 +2151,10 @@ again: qn =3D &tg->qnode_on_parent[rw]; sq =3D sq->parent_sq; tg =3D sq_to_tg(sq); - if (!tg) + if (!tg) { + bio_set_flag(bio, BIO_BPS_THROTTLED); goto out_unlock; + } } =20 /* out-of-limit, queue to @tg */ @@ -2189,8 +2183,6 @@ again: } =20 out_unlock: - bio_set_flag(bio, BIO_THROTTLED); - #ifdef CONFIG_BLK_DEV_THROTTLING_LOW if (throttled || !td->track_bio_latency) bio->bi_issue.value |=3D BIO_ISSUE_THROTL_SKIP_LATENCY; --- a/block/blk-throttle.h +++ b/block/blk-throttle.h @@ -175,7 +175,7 @@ static inline bool blk_throtl_bio(struct struct throtl_grp *tg =3D blkg_to_tg(bio->bi_blkg); =20 /* no need to throttle bps any more if the bio has been throttled */ - if (bio_flagged(bio, BIO_THROTTLED) && + if (bio_flagged(bio, BIO_BPS_THROTTLED) && !(tg->flags & THROTL_TG_HAS_IOPS_LIMIT)) return false; =20 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -509,7 +509,7 @@ static inline void bio_set_dev(struct bi { bio_clear_flag(bio, BIO_REMAPPED); if (bio->bi_bdev !=3D bdev) - bio_clear_flag(bio, BIO_THROTTLED); + bio_clear_flag(bio, BIO_BPS_THROTTLED); bio->bi_bdev =3D bdev; bio_associate_blkg(bio); } --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -323,7 +323,7 @@ enum { BIO_QUIET, /* Make BIO Quiet */ BIO_CHAIN, /* chained bio, ->bi_remaining in effect */ BIO_REFFED, /* bio has elevated ->bi_cnt */ - BIO_THROTTLED, /* This bio has already been subjected to + BIO_BPS_THROTTLED, /* This bio has already been subjected to * throttling rules. Don't do it again. */ BIO_TRACE_COMPLETION, /* bio_endio() should trace the final completion * of this bio. */