From patchwork Tue Jun 8 01:31:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305025 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 D3D2AC47082 for ; Tue, 8 Jun 2021 01:31:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B81F6610C7 for ; Tue, 8 Jun 2021 01:31:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231192AbhFHBd1 (ORCPT ); Mon, 7 Jun 2021 21:33:27 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:59568 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230330AbhFHBd0 (ORCPT ); Mon, 7 Jun 2021 21:33:26 -0400 Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 1581SqT3008134 for ; Mon, 7 Jun 2021 18:31:34 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=mE4STUqPVfkwzOIZnLmRGQso//karXsF28k8p/+rgJA=; b=Uou5UW1Ssfm0ulvzVe1RP8+ZRHrHm2NjT9KRnnT7a8sFxLEpJfD0CMqdTqxQMntsNiCQ 8KHLoA3FfMNW1bO9UaqaU9gyZtPnAHcLgjCbh7dye/U6vTqEYaMTiSyDYxK3N9Q+kaa0 9MmfkAoeQs15M2sfFLqi5koWWkueIbiBPjw= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 390s14se8x-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 07 Jun 2021 18:31:34 -0700 Received: from intmgw002.46.prn1.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:21d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:31:31 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 8C0E081D6D43; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 1/8] writeback, cgroup: do not switch inodes with I_WILL_FREE flag Date: Mon, 7 Jun 2021 18:31:16 -0700 Message-ID: <20210608013123.1088882-2-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: jCqc9XwJoB20jICiyPQbebMoMVFcJ7Rk X-Proofpoint-GUID: jCqc9XwJoB20jICiyPQbebMoMVFcJ7Rk X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 mlxscore=0 malwarescore=0 spamscore=0 priorityscore=1501 adultscore=0 suspectscore=0 phishscore=0 mlxlogscore=977 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080007 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org If an inode's state has I_WILL_FREE flag set, the inode will be freed soon, so there is no point in trying to switch the inode to a different cgwb. I_WILL_FREE was ignored since the introduction of the inode switching, so it looks like it doesn't lead to any noticeable issues for a user. This is why the patch is not intended for a stable backport. Suggested-by: Jan Kara Signed-off-by: Roman Gushchin Acked-by: Tejun Heo Reviewed-by: Jan Kara Acked-by: Dennis Zhou --- fs/fs-writeback.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index e91980f49388..bd99890599e0 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -389,10 +389,10 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) xa_lock_irq(&mapping->i_pages); /* - * Once I_FREEING is visible under i_lock, the eviction path owns - * the inode and we shouldn't modify ->i_io_list. + * Once I_FREEING or I_WILL_FREE are visible under i_lock, the eviction + * path owns the inode and we shouldn't modify ->i_io_list. */ - if (unlikely(inode->i_state & I_FREEING)) + if (unlikely(inode->i_state & (I_FREEING | I_WILL_FREE))) goto skip_switch; trace_inode_switch_wbs(inode, old_wb, new_wb); @@ -517,7 +517,7 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) /* while holding I_WB_SWITCH, no one else can update the association */ spin_lock(&inode->i_lock); if (!(inode->i_sb->s_flags & SB_ACTIVE) || - inode->i_state & (I_WB_SWITCH | I_FREEING) || + inode->i_state & (I_WB_SWITCH | I_FREEING | I_WILL_FREE) || inode_to_wb(inode) == isw->new_wb) { spin_unlock(&inode->i_lock); goto out_free; From patchwork Tue Jun 8 01:31:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305035 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 63026C47095 for ; Tue, 8 Jun 2021 01:31:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 524C6610C7 for ; Tue, 8 Jun 2021 01:31:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231347AbhFHBdj (ORCPT ); Mon, 7 Jun 2021 21:33:39 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:36260 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231342AbhFHBdg (ORCPT ); Mon, 7 Jun 2021 21:33:36 -0400 Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 1581U63V029840 for ; Mon, 7 Jun 2021 18:31:44 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=5HrHHih5juBqYKEEslPOvXicus6WWgPH+iRjEl6TblE=; b=amxgprEku9rCQRvdWBmXu/0dZv4ziiDbMNJ1H+AzjZDyEK4MCtAofsB8BWqiwnlGlCV9 o+B9DsMRcSyLKfce86LYlR5S/ijO3IKbacOzZzKQS6pN5fgSUruVQ1CbruTOxl2VYpSn iwWuHMNyDlaII8Zrs4IKhdjvpmJnmWPwVlk= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 391m0t40uf-5 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 07 Jun 2021 18:31:44 -0700 Received: from intmgw001.05.prn6.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::e) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:31:41 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 9090781D6D45; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 2/8] writeback, cgroup: add smp_mb() to cgroup_writeback_umount() Date: Mon, 7 Jun 2021 18:31:17 -0700 Message-ID: <20210608013123.1088882-3-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: guvaMkzVlK3ZHHKBK2uFXZ2o64XJeNDP X-Proofpoint-ORIG-GUID: guvaMkzVlK3ZHHKBK2uFXZ2o64XJeNDP X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org A full memory barrier is required between clearing SB_ACTIVE flag in generic_shutdown_super() and checking isw_nr_in_flight in cgroup_writeback_umount(), otherwise a new switch operation might be scheduled after atomic_read(&isw_nr_in_flight) returned 0. This would result in a non-flushed isw_wq, and a potential crash. The problem hasn't yet been seen in the real life and was discovered by Jan Kara by looking into the code. Suggested-by: Jan Kara Signed-off-by: Roman Gushchin Reviewed-by: Jan Kara --- fs/fs-writeback.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index bd99890599e0..3564efcc4b78 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1000,6 +1000,12 @@ int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr, */ void cgroup_writeback_umount(void) { + /* + * SB_ACTIVE should be reliably cleared before checking + * isw_nr_in_flight, see generic_shutdown_super(). + */ + smp_mb(); + if (atomic_read(&isw_nr_in_flight)) { /* * Use rcu_barrier() to wait for all pending callbacks to From patchwork Tue Jun 8 01:31:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305057 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 0C2BEC47082 for ; Tue, 8 Jun 2021 01:34:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8CFC61263 for ; Tue, 8 Jun 2021 01:34:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231352AbhFHBgB (ORCPT ); Mon, 7 Jun 2021 21:36:01 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:55298 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230272AbhFHBgA (ORCPT ); Mon, 7 Jun 2021 21:36:00 -0400 Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 1581XwKs003575 for ; Mon, 7 Jun 2021 18:34:08 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=UnR5/HPn3nu3OonRftQmCkI+MWqhatoGojrvOHmp0+Q=; b=I7Kdkfz34jOsjRUVQU6uPuOEAD4BRpnlOa7n4+gbGUK8MLFmcRK7iZyUCmT2cl4n5iWD 9j18LYMIQLGFGtqBtLYkYyrlVdcylSNVFhHFzlWcnCNcdhlSeABRG69P3knc3j+PPOGo rG5dqybsYqQ3EzQmDltzLIf+pg9/9F5fUXU= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 391m0t4154-11 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 07 Jun 2021 18:34:08 -0700 Received: from intmgw001.46.prn1.facebook.com (2620:10d:c085:108::8) by mail.thefacebook.com (2620:10d:c085:21d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:34:03 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 9654F81D6D47; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin , Jan Kara Subject: [PATCH v8 3/8] writeback, cgroup: increment isw_nr_in_flight before grabbing an inode Date: Mon, 7 Jun 2021 18:31:18 -0700 Message-ID: <20210608013123.1088882-4-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: qeOc4D_KFTVkyN-8EkivofehUmiHDLaW X-Proofpoint-ORIG-GUID: qeOc4D_KFTVkyN-8EkivofehUmiHDLaW X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 impostorscore=0 mlxscore=0 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 spamscore=0 lowpriorityscore=0 mlxlogscore=999 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080008 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org isw_nr_in_flight is used do determine whether the inode switch queue should be flushed from the umount path. Currently it's increased after grabbing an inode and even scheduling the switch work. It means the umount path can be walked past cleanup_offline_cgwb() with active inode references, which can result in a "Busy inodes after unmount." message and use-after-free issues (with inode->i_sb which gets freed). Fix it by incrementing isw_nr_in_flight before doing anything with the inode and decrementing in the case when switching wasn't scheduled. The problem hasn't yet been seen in the real life and was discovered by Jan Kara by looking into the code. Suggested-by: Jan Kara Signed-off-by: Roman Gushchin Reviewed-by: Jan Kara --- fs/fs-writeback.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 3564efcc4b78..e2cc860a001b 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -505,6 +505,8 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) if (!isw) return; + atomic_inc(&isw_nr_in_flight); + /* find and pin the new wb */ rcu_read_lock(); memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys); @@ -535,11 +537,10 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) * Let's continue after I_WB_SWITCH is guaranteed to be visible. */ call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn); - - atomic_inc(&isw_nr_in_flight); return; out_free: + atomic_dec(&isw_nr_in_flight); if (isw->new_wb) wb_put(isw->new_wb); kfree(isw); From patchwork Tue Jun 8 01:31:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305031 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 3A589C4743F for ; Tue, 8 Jun 2021 01:31:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2217961182 for ; Tue, 8 Jun 2021 01:31:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231296AbhFHBdd (ORCPT ); Mon, 7 Jun 2021 21:33:33 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:46726 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231261AbhFHBda (ORCPT ); Mon, 7 Jun 2021 21:33:30 -0400 Received: from pps.filterd (m0109334.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 1581SQDk008154 for ; Mon, 7 Jun 2021 18:31:38 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=VOS/cMlJuOP4R8dV3BlKjWy3sUpbjMUwJr4NHNPxER8=; b=UoOInWK62It3F5fZMJ6KYCjtLeW0WB0HC8bX83PE451a4VGo+dcN8KfOEr5xP0d7BaaN AKpYqquQkL+DZtfKVfCqRCL73NkIa3TPJoaHSNQKRBNT+sI36+8twRbmZVX7NaVX9ZiP Ri0kQqbmMo1LdF7OKkyMG09q9jK3zJ/FRCo= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 391mx0ktjc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 07 Jun 2021 18:31:38 -0700 Received: from intmgw001.46.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:31:37 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 9BC5581D6D49; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 4/8] writeback, cgroup: switch to rcu_work API in inode_switch_wbs() Date: Mon, 7 Jun 2021 18:31:19 -0700 Message-ID: <20210608013123.1088882-5-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: SYZ6RLd39GiM8GUewiVhomv7oLPrA9tt X-Proofpoint-ORIG-GUID: SYZ6RLd39GiM8GUewiVhomv7oLPrA9tt X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 priorityscore=1501 impostorscore=0 mlxlogscore=999 mlxscore=0 malwarescore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080007 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Inode's wb switching requires two steps divided by an RCU grace period. It's currently implemented as an RCU callback inode_switch_wbs_rcu_fn(), which schedules inode_switch_wbs_work_fn() as a work. Switching to the rcu_work API allows to do the same in a cleaner and slightly shorter form. Signed-off-by: Roman Gushchin Reviewed-by: Jan Kara Acked-by: Tejun Heo Acked-by: Dennis Zhou --- fs/fs-writeback.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index e2cc860a001b..96974e13a203 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -335,8 +335,7 @@ struct inode_switch_wbs_context { struct inode *inode; struct bdi_writeback *new_wb; - struct rcu_head rcu_head; - struct work_struct work; + struct rcu_work work; }; static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) @@ -352,7 +351,7 @@ static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) static void inode_switch_wbs_work_fn(struct work_struct *work) { struct inode_switch_wbs_context *isw = - container_of(work, struct inode_switch_wbs_context, work); + container_of(to_rcu_work(work), struct inode_switch_wbs_context, work); struct inode *inode = isw->inode; struct backing_dev_info *bdi = inode_to_bdi(inode); struct address_space *mapping = inode->i_mapping; @@ -469,16 +468,6 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) atomic_dec(&isw_nr_in_flight); } -static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head) -{ - struct inode_switch_wbs_context *isw = container_of(rcu_head, - struct inode_switch_wbs_context, rcu_head); - - /* needs to grab bh-unsafe locks, bounce to work item */ - INIT_WORK(&isw->work, inode_switch_wbs_work_fn); - queue_work(isw_wq, &isw->work); -} - /** * inode_switch_wbs - change the wb association of an inode * @inode: target inode @@ -536,7 +525,8 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) * lock so that stat transfer can synchronize against them. * Let's continue after I_WB_SWITCH is guaranteed to be visible. */ - call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn); + INIT_RCU_WORK(&isw->work, inode_switch_wbs_work_fn); + queue_rcu_work(isw_wq, &isw->work); return; out_free: From patchwork Tue Jun 8 01:31:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305037 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 A31EBC47094 for ; Tue, 8 Jun 2021 01:31:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E5D8610C7 for ; Tue, 8 Jun 2021 01:31:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231438AbhFHBdo (ORCPT ); Mon, 7 Jun 2021 21:33:44 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:50028 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231380AbhFHBdi (ORCPT ); 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Mon, 7 Jun 2021 18:31:41 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id A177681D6D4B; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 5/8] writeback, cgroup: keep list of inodes attached to bdi_writeback Date: Mon, 7 Jun 2021 18:31:20 -0700 Message-ID: <20210608013123.1088882-6-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: kfiiaUh0tjLvy5-cTZdA9EcYTX28YtfZ X-Proofpoint-ORIG-GUID: kfiiaUh0tjLvy5-cTZdA9EcYTX28YtfZ X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 impostorscore=0 lowpriorityscore=0 adultscore=0 mlxscore=0 phishscore=0 mlxlogscore=387 suspectscore=0 clxscore=1015 bulkscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080007 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Currently there is no way to iterate over inodes attached to a specific cgwb structure. It limits the ability to efficiently reclaim the writeback structure itself and associated memory and block cgroup structures without scanning all inodes belonging to a sb, which can be prohibitively expensive. While dirty/in-active-writeback an inode belongs to one of the bdi_writeback's io lists: b_dirty, b_io, b_more_io and b_dirty_time. Once cleaned up, it's removed from all io lists. So the inode->i_io_list can be reused to maintain the list of inodes, attached to a bdi_writeback structure. This patch introduces a new wb->b_attached list, which contains all inodes which were dirty at least once and are attached to the given cgwb. Inodes attached to the root bdi_writeback structures are never placed on such list. The following patch will use this list to try to release cgwbs structures more efficiently. Suggested-by: Jan Kara Signed-off-by: Roman Gushchin Reviewed-by: Jan Kara Acked-by: Tejun Heo Acked-by: Dennis Zhou --- fs/fs-writeback.c | 93 ++++++++++++++++++++------------ include/linux/backing-dev-defs.h | 1 + mm/backing-dev.c | 2 + 3 files changed, 62 insertions(+), 34 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 96974e13a203..87b305ee5348 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -131,25 +131,6 @@ static bool inode_io_list_move_locked(struct inode *inode, return false; } -/** - * inode_io_list_del_locked - remove an inode from its bdi_writeback IO list - * @inode: inode to be removed - * @wb: bdi_writeback @inode is being removed from - * - * Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and - * clear %WB_has_dirty_io if all are empty afterwards. - */ -static void inode_io_list_del_locked(struct inode *inode, - struct bdi_writeback *wb) -{ - assert_spin_locked(&wb->list_lock); - assert_spin_locked(&inode->i_lock); - - inode->i_state &= ~I_SYNC_QUEUED; - list_del_init(&inode->i_io_list); - wb_io_lists_depopulated(wb); -} - static void wb_wakeup(struct bdi_writeback *wb) { spin_lock_bh(&wb->work_lock); @@ -278,6 +259,28 @@ void __inode_attach_wb(struct inode *inode, struct page *page) } EXPORT_SYMBOL_GPL(__inode_attach_wb); +/** + * inode_cgwb_move_to_attached - put the inode onto wb->b_attached list + * @inode: inode of interest with i_lock held + * @wb: target bdi_writeback + * + * Remove the inode from wb's io lists and if necessarily put onto b_attached + * list. Only inodes attached to cgwb's are kept on this list. + */ +static void inode_cgwb_move_to_attached(struct inode *inode, + struct bdi_writeback *wb) +{ + assert_spin_locked(&wb->list_lock); + assert_spin_locked(&inode->i_lock); + + inode->i_state &= ~I_SYNC_QUEUED; + if (wb != &wb->bdi->wb) + list_move(&inode->i_io_list, &wb->b_attached); + else + list_del_init(&inode->i_io_list); + wb_io_lists_depopulated(wb); +} + /** * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it * @inode: inode of interest with i_lock held @@ -418,21 +421,28 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) wb_get(new_wb); /* - * Transfer to @new_wb's IO list if necessary. The specific list - * @inode was on is ignored and the inode is put on ->b_dirty which - * is always correct including from ->b_dirty_time. The transfer - * preserves @inode->dirtied_when ordering. + * Transfer to @new_wb's IO list if necessary. If the @inode is dirty, + * the specific list @inode was on is ignored and the @inode is put on + * ->b_dirty which is always correct including from ->b_dirty_time. + * The transfer preserves @inode->dirtied_when ordering. If the @inode + * was clean, it means it was on the b_attached list, so move it onto + * the b_attached list of @new_wb. */ if (!list_empty(&inode->i_io_list)) { - struct inode *pos; - - inode_io_list_del_locked(inode, old_wb); inode->i_wb = new_wb; - list_for_each_entry(pos, &new_wb->b_dirty, i_io_list) - if (time_after_eq(inode->dirtied_when, - pos->dirtied_when)) - break; - inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev); + + if (inode->i_state & I_DIRTY_ALL) { + struct inode *pos; + + list_for_each_entry(pos, &new_wb->b_dirty, i_io_list) + if (time_after_eq(inode->dirtied_when, + pos->dirtied_when)) + break; + inode_io_list_move_locked(inode, new_wb, + pos->i_io_list.prev); + } else { + inode_cgwb_move_to_attached(inode, new_wb); + } } else { inode->i_wb = new_wb; } @@ -1021,6 +1031,17 @@ fs_initcall(cgroup_writeback_init); static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { } static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) { } +static void inode_cgwb_move_to_attached(struct inode *inode, + struct bdi_writeback *wb) +{ + assert_spin_locked(&wb->list_lock); + assert_spin_locked(&inode->i_lock); + + inode->i_state &= ~I_SYNC_QUEUED; + list_del_init(&inode->i_io_list); + wb_io_lists_depopulated(wb); +} + static struct bdi_writeback * locked_inode_to_wb_and_lock_list(struct inode *inode) __releases(&inode->i_lock) @@ -1121,7 +1142,11 @@ void inode_io_list_del(struct inode *inode) wb = inode_to_wb_and_lock_list(inode); spin_lock(&inode->i_lock); - inode_io_list_del_locked(inode, wb); + + inode->i_state &= ~I_SYNC_QUEUED; + list_del_init(&inode->i_io_list); + wb_io_lists_depopulated(wb); + spin_unlock(&inode->i_lock); spin_unlock(&wb->list_lock); } @@ -1434,7 +1459,7 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, inode->i_state &= ~I_SYNC_QUEUED; } else { /* The inode is clean. Remove from writeback lists. */ - inode_io_list_del_locked(inode, wb); + inode_cgwb_move_to_attached(inode, wb); } } @@ -1586,7 +1611,7 @@ static int writeback_single_inode(struct inode *inode, * responsible for the writeback lists. */ if (!(inode->i_state & I_DIRTY_ALL)) - inode_io_list_del_locked(inode, wb); + inode_cgwb_move_to_attached(inode, wb); spin_unlock(&wb->list_lock); inode_sync_complete(inode); out: diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index fff9367a6348..e5dc238ebe4f 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -154,6 +154,7 @@ struct bdi_writeback { struct cgroup_subsys_state *blkcg_css; /* and blkcg */ struct list_head memcg_node; /* anchored at memcg->cgwb_list */ struct list_head blkcg_node; /* anchored at blkcg->cgwb_list */ + struct list_head b_attached; /* attached inodes, protected by list_lock */ union { struct work_struct release_work; diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 576220acd686..54c5dc4b8c24 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -396,6 +396,7 @@ static void cgwb_release_workfn(struct work_struct *work) fprop_local_destroy_percpu(&wb->memcg_completions); percpu_ref_exit(&wb->refcnt); wb_exit(wb); + WARN_ON_ONCE(!list_empty(&wb->b_attached)); kfree_rcu(wb, rcu); } @@ -472,6 +473,7 @@ static int cgwb_create(struct backing_dev_info *bdi, wb->memcg_css = memcg_css; wb->blkcg_css = blkcg_css; + INIT_LIST_HEAD(&wb->b_attached); INIT_WORK(&wb->release_work, cgwb_release_workfn); set_bit(WB_registered, &wb->state); From patchwork Tue Jun 8 01:31:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305039 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 53F6FC48BCF for ; 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Mon, 07 Jun 2021 18:31:53 -0700 Received: from intmgw001.46.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:31:37 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id A70FF81D6D4D; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 6/8] writeback, cgroup: split out the functional part of inode_switch_wbs_work_fn() Date: Mon, 7 Jun 2021 18:31:21 -0700 Message-ID: <20210608013123.1088882-7-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: P1a4EfWtnUAuguYT5pdSwPubMtAZhl-F X-Proofpoint-GUID: P1a4EfWtnUAuguYT5pdSwPubMtAZhl-F X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 phishscore=0 clxscore=1015 malwarescore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 impostorscore=0 mlxlogscore=950 priorityscore=1501 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080007 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Split out the functional part of the inode_switch_wbs_work_fn() function as inode_do switch_wbs() to reuse it later for switching inodes attached to dying cgwbs. This commit doesn't bring any functional changes. Signed-off-by: Roman Gushchin Reviewed-by: Jan Kara Acked-by: Tejun Heo Acked-by: Dennis Zhou --- fs/fs-writeback.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 87b305ee5348..5520a6b5cc4d 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -351,15 +351,12 @@ static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) up_write(&bdi->wb_switch_rwsem); } -static void inode_switch_wbs_work_fn(struct work_struct *work) +static void inode_do_switch_wbs(struct inode *inode, + struct bdi_writeback *new_wb) { - struct inode_switch_wbs_context *isw = - container_of(to_rcu_work(work), struct inode_switch_wbs_context, work); - struct inode *inode = isw->inode; struct backing_dev_info *bdi = inode_to_bdi(inode); struct address_space *mapping = inode->i_mapping; struct bdi_writeback *old_wb = inode->i_wb; - struct bdi_writeback *new_wb = isw->new_wb; XA_STATE(xas, &mapping->i_pages, 0); struct page *page; bool switched = false; @@ -470,11 +467,17 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) wb_wakeup(new_wb); wb_put(old_wb); } - wb_put(new_wb); +} - iput(inode); - kfree(isw); +static void inode_switch_wbs_work_fn(struct work_struct *work) +{ + struct inode_switch_wbs_context *isw = + container_of(to_rcu_work(work), struct inode_switch_wbs_context, work); + inode_do_switch_wbs(isw->inode, isw->new_wb); + wb_put(isw->new_wb); + iput(isw->inode); + kfree(isw); atomic_dec(&isw_nr_in_flight); } From patchwork Tue Jun 8 01:31:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305027 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 D5C20C48BCD for ; 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Mon, 07 Jun 2021 18:31:34 -0700 Received: from intmgw003.48.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:31:33 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id AC39081D6D4F; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 7/8] writeback, cgroup: support switching multiple inodes at once Date: Mon, 7 Jun 2021 18:31:22 -0700 Message-ID: <20210608013123.1088882-8-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: PWvRqIZ-tXPfRATHJ8azLaG9zzqMAdHD X-Proofpoint-ORIG-GUID: PWvRqIZ-tXPfRATHJ8azLaG9zzqMAdHD X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 impostorscore=0 mlxscore=0 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 spamscore=0 lowpriorityscore=0 mlxlogscore=933 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080007 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Currently only a single inode can be switched to another writeback structure at once. That means to switch an inode a separate inode_switch_wbs_context structure must be allocated, and a separate rcu callback and work must be scheduled. It's fine for the existing ad-hoc switching, which is not happening that often, but sub-optimal for massive switching required in order to release a writeback structure. To prepare for it, let's add a support for switching multiple inodes at once. Instead of containing a single inode pointer, inode_switch_wbs_context will contain a NULL-terminated array of inode pointers. inode_do_switch_wbs() will be called for each inode. To optimize the locking bdi->wb_switch_rwsem, old_wb's and new_wb's list_locks will be acquired and released only once altogether for all inodes. wb_wakeup() will be also be called only once. Instead of calling wb_put(old_wb) after each successful switch, wb_put_many() is introduced and used. Signed-off-by: Roman Gushchin Acked-by: Tejun Heo Reviewed-by: Jan Kara Acked-by: Dennis Zhou --- fs/fs-writeback.c | 106 +++++++++++++++++++------------ include/linux/backing-dev-defs.h | 18 +++++- 2 files changed, 80 insertions(+), 44 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 5520a6b5cc4d..737ac27adb77 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -335,10 +335,18 @@ static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) } struct inode_switch_wbs_context { - struct inode *inode; - struct bdi_writeback *new_wb; - struct rcu_work work; + + /* + * Multiple inodes can be switched at once. The switching procedure + * consists of two parts, separated by a RCU grace period. To make + * sure that the second part is executed for each inode gone through + * the first part, all inode pointers are placed into a NULL-terminated + * array embedded into struct inode_switch_wbs_context. Otherwise + * an inode could be left in a non-consistent state. + */ + struct bdi_writeback *new_wb; + struct inode *inodes[]; }; static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) @@ -351,39 +359,15 @@ static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) up_write(&bdi->wb_switch_rwsem); } -static void inode_do_switch_wbs(struct inode *inode, +static bool inode_do_switch_wbs(struct inode *inode, + struct bdi_writeback *old_wb, struct bdi_writeback *new_wb) { - struct backing_dev_info *bdi = inode_to_bdi(inode); struct address_space *mapping = inode->i_mapping; - struct bdi_writeback *old_wb = inode->i_wb; XA_STATE(xas, &mapping->i_pages, 0); struct page *page; bool switched = false; - /* - * If @inode switches cgwb membership while sync_inodes_sb() is - * being issued, sync_inodes_sb() might miss it. Synchronize. - */ - down_read(&bdi->wb_switch_rwsem); - - /* - * By the time control reaches here, RCU grace period has passed - * since I_WB_SWITCH assertion and all wb stat update transactions - * between unlocked_inode_to_wb_begin/end() are guaranteed to be - * synchronizing against the i_pages lock. - * - * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock - * gives us exclusion against all wb related operations on @inode - * including IO list manipulations and stat updates. - */ - if (old_wb < new_wb) { - spin_lock(&old_wb->list_lock); - spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); - } else { - spin_lock(&new_wb->list_lock); - spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); - } spin_lock(&inode->i_lock); xa_lock_irq(&mapping->i_pages); @@ -458,25 +442,63 @@ static void inode_do_switch_wbs(struct inode *inode, xa_unlock_irq(&mapping->i_pages); spin_unlock(&inode->i_lock); - spin_unlock(&new_wb->list_lock); - spin_unlock(&old_wb->list_lock); - - up_read(&bdi->wb_switch_rwsem); - if (switched) { - wb_wakeup(new_wb); - wb_put(old_wb); - } + return switched; } static void inode_switch_wbs_work_fn(struct work_struct *work) { struct inode_switch_wbs_context *isw = container_of(to_rcu_work(work), struct inode_switch_wbs_context, work); + struct backing_dev_info *bdi = inode_to_bdi(isw->inodes[0]); + struct bdi_writeback *old_wb = isw->inodes[0]->i_wb; + struct bdi_writeback *new_wb = isw->new_wb; + unsigned long nr_switched = 0; + struct inode **inodep; + + /* + * If @inode switches cgwb membership while sync_inodes_sb() is + * being issued, sync_inodes_sb() might miss it. Synchronize. + */ + down_read(&bdi->wb_switch_rwsem); + + /* + * By the time control reaches here, RCU grace period has passed + * since I_WB_SWITCH assertion and all wb stat update transactions + * between unlocked_inode_to_wb_begin/end() are guaranteed to be + * synchronizing against the i_pages lock. + * + * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock + * gives us exclusion against all wb related operations on @inode + * including IO list manipulations and stat updates. + */ + if (old_wb < new_wb) { + spin_lock(&old_wb->list_lock); + spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); + } else { + spin_lock(&new_wb->list_lock); + spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); + } + + for (inodep = isw->inodes; *inodep; inodep++) { + WARN_ON_ONCE((*inodep)->i_wb != old_wb); + if (inode_do_switch_wbs(*inodep, old_wb, new_wb)) + nr_switched++; + } + + spin_unlock(&new_wb->list_lock); + spin_unlock(&old_wb->list_lock); + + up_read(&bdi->wb_switch_rwsem); + + if (nr_switched) { + wb_wakeup(new_wb); + wb_put_many(old_wb, nr_switched); + } - inode_do_switch_wbs(isw->inode, isw->new_wb); - wb_put(isw->new_wb); - iput(isw->inode); + for (inodep = isw->inodes; *inodep; inodep++) + iput(*inodep); + wb_put(new_wb); kfree(isw); atomic_dec(&isw_nr_in_flight); } @@ -503,7 +525,7 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) if (atomic_read(&isw_nr_in_flight) > WB_FRN_MAX_IN_FLIGHT) return; - isw = kzalloc(sizeof(*isw), GFP_ATOMIC); + isw = kzalloc(sizeof(*isw) + 2 * sizeof(struct inode *), GFP_ATOMIC); if (!isw) return; @@ -530,7 +552,7 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) __iget(inode); spin_unlock(&inode->i_lock); - isw->inode = inode; + isw->inodes[0] = inode; /* * In addition to synchronizing among switchers, I_WB_SWITCH tells diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index e5dc238ebe4f..63f52ad2ce7a 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -240,8 +240,9 @@ static inline void wb_get(struct bdi_writeback *wb) /** * wb_put - decrement a wb's refcount * @wb: bdi_writeback to put + * @nr: number of references to put */ -static inline void wb_put(struct bdi_writeback *wb) +static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr) { if (WARN_ON_ONCE(!wb->bdi)) { /* @@ -252,7 +253,16 @@ static inline void wb_put(struct bdi_writeback *wb) } if (wb != &wb->bdi->wb) - percpu_ref_put(&wb->refcnt); + percpu_ref_put_many(&wb->refcnt, nr); +} + +/** + * wb_put - decrement a wb's refcount + * @wb: bdi_writeback to put + */ +static inline void wb_put(struct bdi_writeback *wb) +{ + wb_put_many(wb, 1); } /** @@ -281,6 +291,10 @@ static inline void wb_put(struct bdi_writeback *wb) { } +static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr) +{ +} + static inline bool wb_dying(struct bdi_writeback *wb) { return false; From patchwork Tue Jun 8 01:31:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12305029 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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 5CE38C48BCF for ; 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Mon, 07 Jun 2021 18:31:34 -0700 Received: from intmgw002.48.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::e) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 7 Jun 2021 18:31:33 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id B1A3C81D6D51; Mon, 7 Jun 2021 18:31:29 -0700 (PDT) From: Roman Gushchin To: Jan Kara , Tejun Heo CC: , , , Alexander Viro , Dennis Zhou , Dave Chinner , , Roman Gushchin Subject: [PATCH v8 8/8] writeback, cgroup: release dying cgwbs by switching attached inodes Date: Mon, 7 Jun 2021 18:31:23 -0700 Message-ID: <20210608013123.1088882-9-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210608013123.1088882-1-guro@fb.com> References: <20210608013123.1088882-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: F8ASGLEoSVH2qM-sGz2wAetTwjnRHBib X-Proofpoint-GUID: F8ASGLEoSVH2qM-sGz2wAetTwjnRHBib X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-08_01:2021-06-04,2021-06-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 phishscore=0 clxscore=1015 malwarescore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 impostorscore=0 mlxlogscore=384 priorityscore=1501 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106080007 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Asynchronously try to release dying cgwbs by switching attached inodes to the nearest living ancestor wb. It helps to get rid of per-cgroup writeback structures themselves and of pinned memory and block cgroups, which are significantly larger structures (mostly due to large per-cpu statistics data). This prevents memory waste and helps to avoid different scalability problems caused by large piles of dying cgroups. Reuse the existing mechanism of inode switching used for foreign inode detection. To speed things up batch up to 115 inode switching in a single operation (the maximum number is selected so that the resulting struct inode_switch_wbs_context can fit into 1024 bytes). Because every switching consists of two steps divided by an RCU grace period, it would be too slow without batching. Please note that the whole batch counts as a single operation (when increasing/decreasing isw_nr_in_flight). This allows to keep umounting working (flush the switching queue), however prevents cleanups from consuming the whole switching quota and effectively blocking the frn switching. A cgwb cleanup operation can fail due to different reasons (e.g. not enough memory, the cgwb has an in-flight/pending io, an attached inode in a wrong state, etc). In this case the next scheduled cleanup will make a new attempt. An attempt is made each time a new cgwb is offlined (in other words a memcg and/or a blkcg is deleted by a user). In the future an additional attempt scheduled by a timer can be implemented. Signed-off-by: Roman Gushchin Acked-by: Tejun Heo Acked-by: Dennis Zhou Reviewed-by: Jan Kara --- fs/fs-writeback.c | 102 ++++++++++++++++++++++++++++--- include/linux/backing-dev-defs.h | 1 + include/linux/writeback.h | 1 + mm/backing-dev.c | 67 +++++++++++++++++++- 4 files changed, 159 insertions(+), 12 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 737ac27adb77..96eb6e6cdbc2 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -225,6 +225,12 @@ void wb_wait_for_completion(struct wb_completion *done) /* one round can affect upto 5 slots */ #define WB_FRN_MAX_IN_FLIGHT 1024 /* don't queue too many concurrently */ +/* + * Maximum inodes per isw. A specific value has been chosen to make + * struct inode_switch_wbs_context fit into 1024 bytes kmalloc. + */ +#define WB_MAX_INODES_PER_ISW 115 + static atomic_t isw_nr_in_flight = ATOMIC_INIT(0); static struct workqueue_struct *isw_wq; @@ -503,6 +509,24 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) atomic_dec(&isw_nr_in_flight); } +static bool inode_prepare_wbs_switch(struct inode *inode, + struct bdi_writeback *new_wb) +{ + /* while holding I_WB_SWITCH, no one else can update the association */ + spin_lock(&inode->i_lock); + if (!(inode->i_sb->s_flags & SB_ACTIVE) || + inode->i_state & (I_WB_SWITCH | I_FREEING | I_WILL_FREE) || + inode_to_wb(inode) == new_wb) { + spin_unlock(&inode->i_lock); + return false; + } + inode->i_state |= I_WB_SWITCH; + __iget(inode); + spin_unlock(&inode->i_lock); + + return true; +} + /** * inode_switch_wbs - change the wb association of an inode * @inode: target inode @@ -540,17 +564,8 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) if (!isw->new_wb) goto out_free; - /* while holding I_WB_SWITCH, no one else can update the association */ - spin_lock(&inode->i_lock); - if (!(inode->i_sb->s_flags & SB_ACTIVE) || - inode->i_state & (I_WB_SWITCH | I_FREEING | I_WILL_FREE) || - inode_to_wb(inode) == isw->new_wb) { - spin_unlock(&inode->i_lock); + if (!inode_prepare_wbs_switch(inode, isw->new_wb)) goto out_free; - } - inode->i_state |= I_WB_SWITCH; - __iget(inode); - spin_unlock(&inode->i_lock); isw->inodes[0] = inode; @@ -571,6 +586,73 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) kfree(isw); } +/** + * cleanup_offline_cgwb - detach associated inodes + * @wb: target wb + * + * Switch all inodes attached to @wb to a nearest living ancestor's wb in order + * to eventually release the dying @wb. Returns %true if not all inodes were + * switched and the function has to be restarted. + */ +bool cleanup_offline_cgwb(struct bdi_writeback *wb) +{ + struct cgroup_subsys_state *memcg_css; + struct inode_switch_wbs_context *isw; + struct inode *inode; + int nr; + bool restart = false; + + isw = kzalloc(sizeof(*isw) + WB_MAX_INODES_PER_ISW * + sizeof(struct inode *), GFP_KERNEL); + if (!isw) + return restart; + + atomic_inc(&isw_nr_in_flight); + + for (memcg_css = wb->memcg_css->parent; memcg_css; + memcg_css = memcg_css->parent) { + isw->new_wb = wb_get_lookup(wb->bdi, memcg_css); + if (isw->new_wb) + break; + } + if (unlikely(!isw->new_wb)) + isw->new_wb = &wb->bdi->wb; /* wb_get() is noop for bdi's wb */ + + nr = 0; + spin_lock(&wb->list_lock); + list_for_each_entry(inode, &wb->b_attached, i_io_list) { + if (!inode_prepare_wbs_switch(inode, isw->new_wb)) + continue; + + isw->inodes[nr++] = inode; + + if (nr >= WB_MAX_INODES_PER_ISW - 1) { + restart = true; + break; + } + } + spin_unlock(&wb->list_lock); + + /* no attached inodes? bail out */ + if (nr == 0) { + atomic_dec(&isw_nr_in_flight); + wb_put(isw->new_wb); + kfree(isw); + return restart; + } + + /* + * In addition to synchronizing among switchers, I_WB_SWITCH tells + * the RCU protected stat update paths to grab the i_page + * lock so that stat transfer can synchronize against them. + * Let's continue after I_WB_SWITCH is guaranteed to be visible. + */ + INIT_RCU_WORK(&isw->work, inode_switch_wbs_work_fn); + queue_rcu_work(isw_wq, &isw->work); + + return restart; +} + /** * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it * @wbc: writeback_control of interest diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index 63f52ad2ce7a..1d7edad9914f 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -155,6 +155,7 @@ struct bdi_writeback { struct list_head memcg_node; /* anchored at memcg->cgwb_list */ struct list_head blkcg_node; /* anchored at blkcg->cgwb_list */ struct list_head b_attached; /* attached inodes, protected by list_lock */ + struct list_head offline_node; /* anchored at offline_cgwbs */ union { struct work_struct release_work; diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 8e5c5bb16e2d..95de51c10248 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -221,6 +221,7 @@ void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page, int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr_pages, enum wb_reason reason, struct wb_completion *done); void cgroup_writeback_umount(void); +bool cleanup_offline_cgwb(struct bdi_writeback *wb); /** * inode_attach_wb - associate an inode with its wb diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 54c5dc4b8c24..faa45027c854 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -371,12 +371,16 @@ static void wb_exit(struct bdi_writeback *wb) #include /* - * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, and memcg->cgwb_list. - * bdi->cgwb_tree is also RCU protected. + * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and + * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected. */ static DEFINE_SPINLOCK(cgwb_lock); static struct workqueue_struct *cgwb_release_wq; +static LIST_HEAD(offline_cgwbs); +static void cleanup_offline_cgwbs_workfn(struct work_struct *work); +static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn); + static void cgwb_release_workfn(struct work_struct *work) { struct bdi_writeback *wb = container_of(work, struct bdi_writeback, @@ -395,6 +399,11 @@ static void cgwb_release_workfn(struct work_struct *work) fprop_local_destroy_percpu(&wb->memcg_completions); percpu_ref_exit(&wb->refcnt); + + spin_lock_irq(&cgwb_lock); + list_del(&wb->offline_node); + spin_unlock_irq(&cgwb_lock); + wb_exit(wb); WARN_ON_ONCE(!list_empty(&wb->b_attached)); kfree_rcu(wb, rcu); @@ -414,6 +423,7 @@ static void cgwb_kill(struct bdi_writeback *wb) WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id)); list_del(&wb->memcg_node); list_del(&wb->blkcg_node); + list_add(&wb->offline_node, &offline_cgwbs); percpu_ref_kill(&wb->refcnt); } @@ -635,6 +645,57 @@ static void cgwb_bdi_unregister(struct backing_dev_info *bdi) mutex_unlock(&bdi->cgwb_release_mutex); } +/** + * cleanup_offline_cgwbs - try to release dying cgwbs + * + * Try to release dying cgwbs by switching attached inodes to the nearest + * living ancestor's writeback. Processed wbs are placed at the end + * of the list to guarantee the forward progress. + * + * Should be called with the acquired cgwb_lock lock, which might + * be released and re-acquired in the process. + */ +static void cleanup_offline_cgwbs_workfn(struct work_struct *work) +{ + struct bdi_writeback *wb; + LIST_HEAD(processed); + + spin_lock_irq(&cgwb_lock); + + while (!list_empty(&offline_cgwbs)) { + wb = list_first_entry(&offline_cgwbs, struct bdi_writeback, + offline_node); + list_move(&wb->offline_node, &processed); + + /* + * If wb is dirty, cleaning up the writeback by switching + * attached inodes will result in an effective removal of any + * bandwidth restrictions, which isn't the goal. Instead, + * it can be postponed until the next time, when all io + * will be likely completed. If in the meantime some inodes + * will get re-dirtied, they should be eventually switched to + * a new cgwb. + */ + if (wb_has_dirty_io(wb)) + continue; + + if (!wb_tryget(wb)) + continue; + + spin_unlock_irq(&cgwb_lock); + while ((cleanup_offline_cgwb(wb))) + cond_resched(); + spin_lock_irq(&cgwb_lock); + + wb_put(wb); + } + + if (!list_empty(&processed)) + list_splice_tail(&processed, &offline_cgwbs); + + spin_unlock_irq(&cgwb_lock); +} + /** * wb_memcg_offline - kill all wb's associated with a memcg being offlined * @memcg: memcg being offlined @@ -651,6 +712,8 @@ void wb_memcg_offline(struct mem_cgroup *memcg) cgwb_kill(wb); memcg_cgwb_list->next = NULL; /* prevent new wb's */ spin_unlock_irq(&cgwb_lock); + + queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work); } /**