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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 6CE4EC388F2 for ; Tue, 3 Nov 2020 01:23:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D261222B9 for ; Tue, 3 Nov 2020 01:23:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604366592; bh=fNHrt/GdcOtMrdpxZLIszplS2BMx/sgK37xpgdSdbCU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YUv+jRtJS/E6gtsduKfi+VrlZsSpNj/+VkuoGXawExo3JCJF0sG0I0+nBJweaAe3M IGLD3n7fze05dR+72QQMKi+jmJTwY5T0LoIIJc4sQNJ1oD2QLjFKKurpOoifbc4KwJ Pgt+tLSwkUcv1MJ9/Oov0sTELZ/j5ysfa2xBXVOM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728028AbgKCBXL (ORCPT ); Mon, 2 Nov 2020 20:23:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:35902 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728220AbgKCBUs (ORCPT ); Mon, 2 Nov 2020 20:20:48 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D3EFA223EA; Tue, 3 Nov 2020 01:20:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604366447; bh=fNHrt/GdcOtMrdpxZLIszplS2BMx/sgK37xpgdSdbCU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dyO4UuiIP74n6/k3/L0QiwGw29/e/nNsinYK6kRi/0BJ9qamfU9lXlBy5Xa0duj+g 4NvpJMBK3fFsgjOCslhijWFKZ6sW5af+2gb3B2osH1d7ybh4L6jICABTmYs//acDCj arCJBSVpewuD4oxpQAdqEDLBI/KqxtCY/Fwm128E= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Gabriel Krisman Bertazi , Tejun Heo , Jens Axboe , Sasha Levin , cgroups@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 06/11] blk-cgroup: Pre-allocate tree node on blkg_conf_prep Date: Mon, 2 Nov 2020 20:20:34 -0500 Message-Id: <20201103012039.183672-6-sashal@kernel.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20201103012039.183672-1-sashal@kernel.org> References: <20201103012039.183672-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Gabriel Krisman Bertazi [ Upstream commit f255c19b3ab46d3cad3b1b2e1036f4c926cb1d0c ] Similarly to commit 457e490f2b741 ("blkcg: allocate struct blkcg_gq outside request queue spinlock"), blkg_create can also trigger occasional -ENOMEM failures at the radix insertion because any allocation inside blkg_create has to be non-blocking, making it more likely to fail. This causes trouble for userspace tools trying to configure io weights who need to deal with this condition. This patch reduces the occurrence of -ENOMEMs on this path by preloading the radix tree element on a GFP_KERNEL context, such that we guarantee the later non-blocking insertion won't fail. A similar solution exists in blkcg_init_queue for the same situation. Acked-by: Tejun Heo Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-cgroup.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 51fc803c999d7..85bd46e0a745f 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -876,6 +876,12 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, goto fail; } + if (radix_tree_preload(GFP_KERNEL)) { + blkg_free(new_blkg); + ret = -ENOMEM; + goto fail; + } + rcu_read_lock(); spin_lock_irq(q->queue_lock); @@ -883,7 +889,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, if (IS_ERR(blkg)) { ret = PTR_ERR(blkg); blkg_free(new_blkg); - goto fail_unlock; + goto fail_preloaded; } if (blkg) { @@ -892,10 +898,12 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, blkg = blkg_create(pos, q, new_blkg); if (unlikely(IS_ERR(blkg))) { ret = PTR_ERR(blkg); - goto fail_unlock; + goto fail_preloaded; } } + radix_tree_preload_end(); + if (pos == blkcg) goto success; } @@ -905,6 +913,8 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, ctx->body = body; return 0; +fail_preloaded: + radix_tree_preload_end(); fail_unlock: spin_unlock_irq(q->queue_lock); rcu_read_unlock(); -- 2.27.0