From patchwork Sun Dec 11 22:20:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 13070671 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51C9CC4332F for ; Sun, 11 Dec 2022 22:21:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DBD088E0003; Sun, 11 Dec 2022 17:21:14 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D6D4A8E0002; Sun, 11 Dec 2022 17:21:14 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C357F8E0003; Sun, 11 Dec 2022 17:21:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id B0FEE8E0002 for ; Sun, 11 Dec 2022 17:21:14 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 95C40808FA for ; Sun, 11 Dec 2022 22:21:14 +0000 (UTC) X-FDA: 80231447268.21.5EF6C42 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf17.hostedemail.com (Postfix) with ESMTP id 0701D40008 for ; Sun, 11 Dec 2022 22:21:11 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LG2acMN2; spf=pass (imf17.hostedemail.com: domain of longman@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1670797272; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+MsWk87quHbEwHCR1sVYteGgGZjHdGBkMWIDf/Jp0nk=; b=Fe4+yVcHRib1h/6lHsZtgDyZA2G28/oiNh33BhZrfbqqF2IwyVVuA/iRuPWO6gESRsMJUR 9Bv62lzvh2gVwR117FzrD2PYZjWQFELZ3dEx3KalpINekR7lGoD+DpNOhNrj615NBISOVp AMi+Ev2lo9up6A9A5wXa+j/o8YtKg10= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LG2acMN2; spf=pass (imf17.hostedemail.com: domain of longman@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1670797272; a=rsa-sha256; cv=none; b=u9uToVolR4jNEUI9hmy5tZDsw773G/SjMdEpWrn4JRpQVBikxuY2jegxGKA8C9ov4SVeG6 Ek0LU70gkl9qYhcHCpYwTHztIPXQUtRAonNvLm33dpmWS847qyImf7z4MsQlXlsux/rx8+ hMv/5lT/oY0M8VBbHguh/HEKOFImZ68= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670797271; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+MsWk87quHbEwHCR1sVYteGgGZjHdGBkMWIDf/Jp0nk=; b=LG2acMN2TQiHjgL/l0Q4UWV/5J9BfFbH+TdCh2PDalr6IjIFRlZSJ9Lv6KOxs2FsR2rCkr /UGr4e/tIvNhN+piok0ClULPu7bpfHDqWU5AAshheeOHEy43l+XvbkvVc0ld1WvztRxvBi HwRAs9YphhWubrgGIt6yU3pwYHyNw+o= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-478-dS9F4qTYMZGQE_Cocb_m5Q-1; Sun, 11 Dec 2022 17:21:08 -0500 X-MC-Unique: dS9F4qTYMZGQE_Cocb_m5Q-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9496C101A56C; Sun, 11 Dec 2022 22:21:07 +0000 (UTC) Received: from llong.com (unknown [10.22.16.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id 073EF1121331; Sun, 11 Dec 2022 22:21:06 +0000 (UTC) From: Waiman Long To: Jens Axboe , Tejun Heo , Josef Bacik , Zefan Li , Johannes Weiner , Andrew Morton Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?utf-8?q?Michal_Koutn?= =?utf-8?q?=C3=BD?= , "Dennis Zhou (Facebook)" , Waiman Long , Yi Zhang Subject: [PATCH-block v2 1/3] bdi, blk-cgroup: Fix potential UAF of blkcg Date: Sun, 11 Dec 2022 17:20:56 -0500 Message-Id: <20221211222058.2946830-2-longman@redhat.com> In-Reply-To: <20221211222058.2946830-1-longman@redhat.com> References: <20221211222058.2946830-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspamd-Queue-Id: 0701D40008 X-Stat-Signature: x6jjkp99tk4ni4xxii51fkx6oso14p58 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1670797271-321244 X-HE-Meta: U2FsdGVkX18RJJ5RNCwvwbbCGCjZIdWhjt9Rlef9BpnzqENlQEKc2iGYT1lOlWbnVVlEI3jBWeC4OlQ6k5pp1YkpXPYqaEbxT2GfxA6M9/0iYjtSCs+ck2GFin7eOsVSDH1BZhQroWGE5PQyTJ2vBCwhtamjFVyTW/zpupWAf9eGZlH9Sn8kIDPUm0PwuHfDE5pzz+JAdnS5ndfxgVdzC/twXSJIgWT3q2jfYGlliBC2k1709Qa6QIbf5JtXqp1x1AoMyqHMp4thxqIVhbJRsc1OEH6k6mhXwbY3Ru8g0amg0pWGkt60lv4NNyC/Bouxs4DvgRfJDr7uNCgXa12MkY4eAdLEGR7PjFBOeC9MYcQ2HTQZMtcal/jIqnSlVK5fVwk/CK5/xSZxswP6yPPG/dMIAYsIajLTPHXcBWDy8Hqp3ZXRkvh5uEQxIxPGxMkK6lBRBCooPcz4N6avEZ2pOrn05jYNkqg/0mlayTYhkhhgbifgV+VuNL8Uk1IxKoapJEisi472o+8RhoVWNU8nvT0G6GpQFhvJJlzP/BY0qcbBCCumpkqX2K4TW/t5d3+hpg2vqimy7vqjMPWPOt6lz/nnMoo6svC/a+1PwQzb13nqaAXak2ZqULAFO3RFSzcUfYt0QeeeSwYCQt8vH8frvaCz7PI26Re1x7jDZEN9U8LzQHVea6FHw6iRXE7xJbyIThIaFH1rzCRQwAZn6QVaJXUcNjPpj78+tTBI2D8duT272G8LCbIdPS3qph4C+kjz1ThLTyF+rgGyjN5wUWMTBnB++jh6YEUrD32kQ+0376ktJffATLmLIzSyPe2/05sT6VlJUUNnSgsD8qfkQqi733f/CvDgEwztDQ5pjA5Uj/Vt1NvaJ5pSiSDDQGOfNj6r X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Commit 59b57717fff8 ("blkcg: delay blkg destruction until after writeback has finished") delayed call to blkcg_destroy_blkgs() to cgwb_release_workfn(). However, it is done after a css_put() of blkcg which may be the final put that causes the blkcg to be freed as RCU read lock isn't held. Another place where blkcg_destroy_blkgs() can be called indirectly via blkcg_unpin_online() is from the offline_css() function called from css_killed_work_fn(). Over there, the potentially final css_put() call is issued after offline_css(). By adding a css_tryget() into blkcg_destroy_blkgs() and warning its failure, the following stack trace was produced in a test system on bootup. [ 34.254240] RIP: 0010:blkcg_destroy_blkgs+0x16a/0x1a0 : [ 34.339943] Call Trace: [ 34.344510] blkcg_unpin_online+0x38/0x60 [ 34.348523] cgwb_release_workfn+0x6a/0x200 [ 34.352708] process_one_work+0x1e5/0x3b0 [ 34.360758] worker_thread+0x50/0x3a0 [ 34.368447] kthread+0xd9/0x100 [ 34.376386] ret_from_fork+0x22/0x30 This confirms that a potential UAF situation can really happen in cgwb_release_workfn(). Fix that by delaying the css_put() until after the blkcg_unpin_online() call. Also use css_tryget() in blkcg_destroy_blkgs() and issue a warning if css_tryget() fails. The reproducing system can no longer produce a warning with this patch. All the runnable block/0* tests including block/027 were run successfully without failure. Fixes: 59b57717fff8 ("blkcg: delay blkg destruction until after writeback has finished") Suggested-by: Michal Koutný Reported-by: Yi Zhang Signed-off-by: Waiman Long --- block/blk-cgroup.c | 8 ++++++++ mm/backing-dev.c | 8 ++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 1bb939d3b793..21cc88349f21 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1084,6 +1084,13 @@ struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css) */ static void blkcg_destroy_blkgs(struct blkcg *blkcg) { + /* + * blkcg_destroy_blkgs() shouldn't be called with all the blkcg + * references gone. + */ + if (WARN_ON_ONCE(!css_tryget(&blkcg->css))) + return; + might_sleep(); spin_lock_irq(&blkcg->lock); @@ -1110,6 +1117,7 @@ static void blkcg_destroy_blkgs(struct blkcg *blkcg) } spin_unlock_irq(&blkcg->lock); + css_put(&blkcg->css); } /** diff --git a/mm/backing-dev.c b/mm/backing-dev.c index c30419a5e119..36f75b072325 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -390,11 +390,15 @@ static void cgwb_release_workfn(struct work_struct *work) wb_shutdown(wb); css_put(wb->memcg_css); - css_put(wb->blkcg_css); mutex_unlock(&wb->bdi->cgwb_release_mutex); - /* triggers blkg destruction if no online users left */ + /* + * Triggers blkg destruction if no online users left + * The final blkcg css_put() has to be done after blkcg_unpin_online() + * to avoid use-after-free. + */ blkcg_unpin_online(wb->blkcg_css); + css_put(wb->blkcg_css); fprop_local_destroy_percpu(&wb->memcg_completions); From patchwork Sun Dec 11 22:20:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 13070673 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97D7EC4167B for ; Sun, 11 Dec 2022 22:21:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B4CA48E0006; Sun, 11 Dec 2022 17:21:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AFF098E0002; Sun, 11 Dec 2022 17:21:16 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C8C78E0006; Sun, 11 Dec 2022 17:21:16 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6C62D8E0002 for ; Sun, 11 Dec 2022 17:21:16 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 4BD53160969 for ; Sun, 11 Dec 2022 22:21:16 +0000 (UTC) X-FDA: 80231447352.13.968B092 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf08.hostedemail.com (Postfix) with ESMTP id C59D0160016 for ; Sun, 11 Dec 2022 22:21:14 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ASonaym8; spf=pass (imf08.hostedemail.com: domain of longman@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1670797274; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=s3VQJPU/3HC+t8N1wzyewiUON5nIdBJkilNRlkYPV+o=; b=mNDNcHEP1hud70enKK3tvFaRfxk9ZuU6XLq/sbt8Se06463FUiS31u4VM4QpboFdsx227n Tp/xIcHifI3jjDdIVUaYJCc4F8WRBc/gbFGDXnVWkV7VPef0Td0DpSmdgi03s12P4JIDEP 2vonBQUwFK8QTivCWYzbto9PKcZ1LlU= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ASonaym8; spf=pass (imf08.hostedemail.com: domain of longman@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1670797274; a=rsa-sha256; cv=none; b=xouMooYLrMVYxRUy+cP5upQvBqqxye3gmQmUEyJg/CqfxdDWpEUA+U5LzBiO9NgoCXzYNO 5scnwD2zAuu4eVKFeVzhq+qhr612x4hrABU41eZFg8jY3X+fR5M2mWeVLR8fd3jUViwgvx 2dY8fesLhoXfC+GJ0n+MJZFHCyvj+yo= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670797274; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=s3VQJPU/3HC+t8N1wzyewiUON5nIdBJkilNRlkYPV+o=; b=ASonaym88z1O3xWD+IMdxPvAG73bznBKHsiGXT1guUu9vqYUAF/psi1bNgq20/otfAOqVH ELggW5NCDzZKV/+vkwCggctSKcc7jp13ipCisSf85T82WwSmd80t6lmoyQloScPVuhbQ6y 7I+SqpsxkfWcFQZUCW+Fd9VYDJQOyiw= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-624-uncOj-fSOjS8G7ZSnT3xYg-1; Sun, 11 Dec 2022 17:21:08 -0500 X-MC-Unique: uncOj-fSOjS8G7ZSnT3xYg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 28D7F1C05138; Sun, 11 Dec 2022 22:21:08 +0000 (UTC) Received: from llong.com (unknown [10.22.16.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id A25191121331; Sun, 11 Dec 2022 22:21:07 +0000 (UTC) From: Waiman Long To: Jens Axboe , Tejun Heo , Josef Bacik , Zefan Li , Johannes Weiner , Andrew Morton Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?utf-8?q?Michal_Koutn?= =?utf-8?q?=C3=BD?= , "Dennis Zhou (Facebook)" , Waiman Long Subject: [PATCH-block v2 2/3] blk-cgroup: Don't flush a blkg if destroyed Date: Sun, 11 Dec 2022 17:20:57 -0500 Message-Id: <20221211222058.2946830-3-longman@redhat.com> In-Reply-To: <20221211222058.2946830-1-longman@redhat.com> References: <20221211222058.2946830-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspamd-Queue-Id: C59D0160016 X-Stat-Signature: tkt8ebfnc1yk88d8rxb93wyadxw4m4oj X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1670797274-825514 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Before commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()"), blkg's stats is only flushed if they are online. In addition, the stat flushing of blkgs in blkcg_rstat_flush() includes propagating the rstat data to its parent. However, if a blkg has been destroyed (offline), the validity of its parent may be questionable. For safety, revert back to the old behavior by ignoring offline blkg's. Signed-off-by: Waiman Long --- block/blk-cgroup.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 21cc88349f21..c466aef0d467 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -885,6 +885,12 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu) WRITE_ONCE(bisc->lqueued, false); + /* Don't flush its stats if blkg is offline */ + if (unlikely(!blkg->online)) { + percpu_ref_put(&blkg->refcnt); + continue; + } + /* fetch the current per-cpu values */ do { seq = u64_stats_fetch_begin(&bisc->sync); From patchwork Sun Dec 11 22:20:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 13070674 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92C23C4332F for ; Sun, 11 Dec 2022 22:21:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3ABBD8E0007; Sun, 11 Dec 2022 17:21:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 335288E0002; Sun, 11 Dec 2022 17:21:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0785E8E0007; Sun, 11 Dec 2022 17:21:16 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id E9B1A8E0002 for ; Sun, 11 Dec 2022 17:21:16 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id BA75740998 for ; Sun, 11 Dec 2022 22:21:16 +0000 (UTC) X-FDA: 80231447352.09.22253CA Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf27.hostedemail.com (Postfix) with ESMTP id 4341E40006 for ; Sun, 11 Dec 2022 22:21:15 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RoFalQcb; spf=pass (imf27.hostedemail.com: domain of longman@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1670797275; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=k/HK6fMXdxgz4kcaH4vQrOdm/WfD552GcWScyCwHZ9A=; b=TsOpoUjrnDnfvh1zUcaT9woCnmYXC0n1ddL06FjoFDEOsNBqAMvPT/87FKRkR3gyjd38So Fz3fRCcdDJbn5LgPJb1NykIQFk2YoDvhapuW98WpJwcwppPqniUjG3lYdC/c7dBVW6+Bk6 fhxmJ5XhyF68YNf8s0TTEbz5H9oAxR8= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RoFalQcb; spf=pass (imf27.hostedemail.com: domain of longman@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1670797275; a=rsa-sha256; cv=none; b=ELRXHk/0eEyWNnhzFO2MwBGkVIzEa4ldzb3/NbsJ2jK8xAEN5ziSClfc/eBKE2VQvilGQD QRZmgHul1N10mkzigaer7+QYL+me1kVQCtIJpmTfH309xdyx2teXVx0uOhadTyYXt0ouw0 6ZHuZFErrMl7LbUeYKcvTyvk9oMENjs= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670797274; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=k/HK6fMXdxgz4kcaH4vQrOdm/WfD552GcWScyCwHZ9A=; b=RoFalQcb1pSSuoPUsOqv5uHU/o69MyB3CNVpANKthGZzkwz5/WDHucOFG5haP6GzcCLJku d1S62TDbiih5xQjXgT1GuI7qX1tnSl/sVvFSKsjQEIQH5Ex6hHbdmnLoV247s6i8COTpcg zpqWtEvv7t2NlDwS2o6HuMGmTzmXgVQ= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-567-gXbDyWjHO-mp8qogjpDY2A-1; Sun, 11 Dec 2022 17:21:09 -0500 X-MC-Unique: gXbDyWjHO-mp8qogjpDY2A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B196D3C01D8F; Sun, 11 Dec 2022 22:21:08 +0000 (UTC) Received: from llong.com (unknown [10.22.16.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id 37C721121331; Sun, 11 Dec 2022 22:21:08 +0000 (UTC) From: Waiman Long To: Jens Axboe , Tejun Heo , Josef Bacik , Zefan Li , Johannes Weiner , Andrew Morton Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?utf-8?q?Michal_Koutn?= =?utf-8?q?=C3=BD?= , "Dennis Zhou (Facebook)" , Waiman Long Subject: [PATCH-block v2 3/3] blk-cgroup: Flush stats at blkgs destruction path Date: Sun, 11 Dec 2022 17:20:58 -0500 Message-Id: <20221211222058.2946830-4-longman@redhat.com> In-Reply-To: <20221211222058.2946830-1-longman@redhat.com> References: <20221211222058.2946830-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4341E40006 X-Stat-Signature: 8bnprymkxdqbyzigr5wao6f3hjb65r7a X-Rspam-User: X-HE-Tag: 1670797275-238024 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 from being freed until some other events cause cgroup_rstat_flush() to be called to flush out the pending blkcg stats. To prevent this delayed blkcg removal, add a new cgroup_rstat_css_flush() function to flush stats for a given css and cpu and call it at the blkgs destruction path, blkcg_destroy_blkgs(), whenever there are still some pending stats to be flushed. This will ensure that blkcg reference count can reach 0 ASAP. Signed-off-by: Waiman Long Acked-by: Tejun Heo --- block/blk-cgroup.c | 12 ++++++++++++ include/linux/cgroup.h | 1 + kernel/cgroup/rstat.c | 18 ++++++++++++++++++ 3 files changed, 31 insertions(+) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index c466aef0d467..534f3baeb84a 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1090,6 +1090,8 @@ struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css) */ static void blkcg_destroy_blkgs(struct blkcg *blkcg) { + int cpu; + /* * blkcg_destroy_blkgs() shouldn't be called with all the blkcg * references gone. @@ -1099,6 +1101,16 @@ static void blkcg_destroy_blkgs(struct blkcg *blkcg) might_sleep(); + /* + * Flush all the non-empty percpu lockless lists. + */ + for_each_possible_cpu(cpu) { + struct llist_head *lhead = per_cpu_ptr(blkcg->lhead, cpu); + + if (!llist_empty(lhead)) + cgroup_rstat_css_cpu_flush(&blkcg->css, cpu); + } + spin_lock_irq(&blkcg->lock); while (!hlist_empty(&blkcg->blkg_list)) { diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 528bd44b59e2..6c4e66b3fa84 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -766,6 +766,7 @@ void cgroup_rstat_flush(struct cgroup *cgrp); void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp); void cgroup_rstat_flush_hold(struct cgroup *cgrp); void cgroup_rstat_flush_release(void); +void cgroup_rstat_css_cpu_flush(struct cgroup_subsys_state *css, int cpu); /* * Basic resource stats. diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index 793ecff29038..2e44be44351f 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -281,6 +281,24 @@ void cgroup_rstat_flush_release(void) spin_unlock_irq(&cgroup_rstat_lock); } +/** + * cgroup_rstat_css_cpu_flush - flush stats for the given css and cpu + * @css: target css to be flush + * @cpu: the cpu that holds the stats to be flush + * + * A lightweight rstat flush operation for a given css and cpu. + * Only the cpu_lock is being held for mutual exclusion, the cgroup_rstat_lock + * isn't used. + */ +void cgroup_rstat_css_cpu_flush(struct cgroup_subsys_state *css, int cpu) +{ + raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu); + + raw_spin_lock_irq(cpu_lock); + css->ss->css_rstat_flush(css, cpu); + raw_spin_unlock_irq(cpu_lock); +} + int cgroup_rstat_init(struct cgroup *cgrp) { int cpu;