From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A248736E466; Tue, 13 Oct 2026 12:20:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894017; cv=none; b=FSMoupVe+kZAud9a5HuR9+WBDETURauLbBEKiEwyp5pTApBa9UD28jiMk0zyZXtD2vzB9fzhjW9UiK8LYGwpx3MXofhna1snVtT0gu42Kl2qUIaESxTEZR0Z13SNvO7EYoD/GzdCg4bDMqyGbtMu834zFRYXY8O34krJaVeVDY0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894017; c=relaxed/simple; bh=xGPMyWJ2Dy1R1yqfIi/ZRvnVI3up/SlfbV8LE1zdTDE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=giAbH6IPnCQy3e4hJUndFtFjSv2sz2OxsT+kEXSHr7aEHSQjdeoNDThek/Z7ZTkvblxHu6NUAurFaWoqAJaTp236pkrjckS2FgMpxjqYGwFTJ6lr7Vrvkvqaq8CGMM2LEqdYkaYobvCWIqxs4qamCY0F3t0lKQUbyxOIxc21WnI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2oJ/oVHI; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2oJ/oVHI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE4F01F000FF; Tue, 13 Oct 2026 12:20:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791894016; bh=SOk7QZJfxebM5nfHgyPmdrtKUocKufIdsOAgy2MpLYg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=2oJ/oVHIT2AZRzWCOxkefbKLYV2moja7TyilFosyaFkLQpXBnN22wx2+HZd8faui9 esbUdv53w6N/Hy2zDmxFzxALeNb30nPpgNjIfedZYTdvXa6/HQHCoZPRzi0HibH7sN AyfWX+pIgmH1wPT6e3VoPZPsCsCw+8ave2SXeIYI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Usama Arif , Tejun Heo , Jens Axboe , Sasha Levin Subject: [PATCH 6.18 418/621] blk-iolatency: clear delay state when freeing policy data Date: Tue, 13 Oct 2026 13:36:53 +0200 Message-ID: <20261013112930.755792917@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Usama Arif [ Upstream commit 8935bf22c0a0db517a7f72f7097300e05dd852f5 ] io.latency can throttle a group which has no latency target of its own. When a sibling misses its target, check_scale_change() scales down its peers, and a peer that reaches queue depth one gets blkcg_use_delay() called on it on every further scale-down, even with min_lat_nsec == 0. iolatency_pd_offline() resets the target through iolatency_set_min_lat_nsec(), which clears the delay only on a nonzero to zero transition, so it never clears such a peer. Freeing the policy data then leaves blkg->use_delay set and blkcg->congestion_count elevated with nothing left that can drop it. blk_cgroup_congested() then returns true for every task in that cgroup and its descendants for as long as the cgroup lives: page_cache_sync_ra() cuts readahead to a single page, page_cache_async_ra() skips it altogether, and __folio_throttle_swaprate() takes swap_avail_lock and schedules a throttle on anonymous folio allocation. Clear the delay in iolatency_pd_free(). By then bio-held blkg references have drained, or the queue is frozen for policy deactivation, so check_scale_change() cannot re-arm it. The free callback can also see policy data which was never attached to a blkg, hence the pd->blkg check. Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Signed-off-by: Usama Arif Acked-by: Tejun Heo Link: https://patch.msgid.link/20260814165712.510132-2-usama.arif@linux.dev Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-iolatency.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index ce25fbb8aaf66..17e530b93c48c 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c @@ -1043,6 +1043,15 @@ static void iolat_release(struct rcu_head *rcu) static void iolatency_pd_free(struct blkg_policy_data *pd) { + struct blkcg_gq *blkg = pd_to_blkg(pd); + + /* + * Groups throttled as collateral have min_lat_nsec == 0, so + * iolatency_pd_offline() leaves their delay set. Drop it here, where + * no in-flight bio can re-arm it via check_scale_change(). + */ + if (blkg) + blkcg_clear_delay(blkg); call_rcu(&pd->rcu_head, iolat_release); } -- 2.53.0