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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C209EB64DB for ; Mon, 19 Jun 2023 10:15:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229846AbjFSKPR (ORCPT ); Mon, 19 Jun 2023 06:15:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231915AbjFSKOt (ORCPT ); Mon, 19 Jun 2023 06:14:49 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3E0FE58; Mon, 19 Jun 2023 03:14:45 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6990960A50; Mon, 19 Jun 2023 10:14:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78F55C433C9; Mon, 19 Jun 2023 10:14:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687169684; bh=Zuhm6jIOghtFuLke9BGwHGq/HQJPt6fx2PoAZUwJ/dY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SrqOeppkzCsYtK6/tBsxdHf1MJpIjnQx2PcC4vKdLNXI1R+pc9g154gfmQQeIms+C GsoEQZ8qeeheT8PBmAltXFzKi+oUKJ5f9oGsD76MR31Qj+Kdx+vEMdmTIOb9+W/Zjo kYpSBgKoTW7c0lLJ5sO6C/EHRXHtq4LNTFYKovj0= Date: Mon, 19 Jun 2023 12:14:42 +0200 From: Greg Kroah-Hartman To: Ming Lei Cc: stable@vger.kernel.org, Jens Axboe , linux-block@vger.kernel.org, Jay Shin , Tejun Heo , Waiman Long , mkoutny@suse.com, Yosry Ahmed Subject: Re: [PATCH 6.3.y] blk-cgroup: Flush stats before releasing blkcg_gq Message-ID: <2023061933-corporate-overkill-e24a@gregkh> References: <20230619083009.743135-1-ming.lei@redhat.com> <2023061901-fleshed-patrol-afc4@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Jun 19, 2023 at 05:20:19PM +0800, Ming Lei wrote: > On Mon, Jun 19, 2023 at 10:51:16AM +0200, Greg Kroah-Hartman wrote: > > On Mon, Jun 19, 2023 at 04:30:09PM +0800, Ming Lei wrote: > > > As noted by Michal, the blkg_iostat_set's in the lockless list hold > > > reference to blkg's to protect against their removal. Those blkg's > > > hold reference to blkcg. When a cgroup is being destroyed, > > > cgroup_rstat_flush() is only called at css_release_work_fn() which > > > is called when the blkcg reference count reaches 0. This circular > > > dependency will prevent blkcg and some blkgs from being freed after > > > they are made offline. > > > > > > It is less a problem if the cgroup to be destroyed also has other > > > controllers like memory that will call cgroup_rstat_flush() which will > > > clean up the reference count. If block is the only controller that uses > > > rstat, these offline blkcg and blkgs may never be freed leaking more > > > and more memory over time. > > > > > > To prevent this potential memory leak: > > > > > > - flush blkcg per-cpu stats list in __blkg_release(), when no new stat > > > can be added > > > > > > - add global blkg_stat_lock for covering concurrent parent blkg stat > > > update > > > > > > - don't grab bio->bi_blkg reference when adding the stats into blkcg's > > > per-cpu stat list since all stats are guaranteed to be consumed before > > > releasing blkg instance, and grabbing blkg reference for stats was the > > > most fragile part of original patch > > > > > > Based on Waiman's patch: > > > > > > https://lore.kernel.org/linux-block/20221215033132.230023-3-longman@redhat.com/ > > > > > > Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") > > > Cc: stable@vger.kernel.org > > > Reported-by: Jay Shin > > > Acked-by: Tejun Heo > > > Cc: Waiman Long > > > Cc: mkoutny@suse.com > > > Cc: Yosry Ahmed > > > Signed-off-by: Ming Lei > > > Link: https://lore.kernel.org/r/20230609234249.1412858-1-ming.lei@redhat.com > > > Signed-off-by: Jens Axboe > > > --- > > > Context difference with linus tree: 2c275afeb61d ("block: make blkcg_punt_bio_submit > > > optional") adds '#ifdef CONFIG_BLK_CGROUP_PUNT_BIO' in __blkg_release(). > > > > > > > > > > What is the git commit id of this change in Linus's tree? > > 20cb1c2fb756 ("blk-cgroup: Flush stats before releasing blkcg_gq") Thanks, now queued up. greg k-h