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 30514C43217 for ; Thu, 10 Nov 2022 20:25:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231650AbiKJUZo (ORCPT ); Thu, 10 Nov 2022 15:25:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229461AbiKJUZl (ORCPT ); Thu, 10 Nov 2022 15:25:41 -0500 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9572D62CE; Thu, 10 Nov 2022 12:25:40 -0800 (PST) Received: from pps.filterd (m0246629.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 2AAKGbOr031700; Thu, 10 Nov 2022 20:25:37 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : in-reply-to : references : date : message-id : content-type : mime-version; s=corp-2022-7-12; bh=4eoowv03BqkL6iv1KoQXDgV5U/jev4KlQOJKxd1WV+E=; b=Epr8QUfm2WFiyIH2rceUgViDVyo/tIZB7mkTPE9zxpZevKLuy/Kc9DnvVd/X8NkU5ow+ JgcFYaLtjXYjaJu2p10WirzTdGXF80sDbcMltrSrv1L4nCEDRBL3LGEkTCnDSuK8LHy4 ASETA4XjnEJJC/sft2xnRAI7gA3+UcTsqjCcDfjJR294n+q/j2iC3PiwLzQPVd+NDtvp 9D5n42GLjt80mWCxC3lF4JNTA2bK0WXpVha/Eg0iBtNW8J3dFiwz1Se89JYsaSPV1Fo1 eUjnQvkr8t+rejqGK3zCM22syMcocSeBpyAHpAnmpaBxSg187bXyAuRSIWvw3LfhsYok Ug== Received: from phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta01.appoci.oracle.com [138.1.114.2]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3ks86hr19e-27 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 10 Nov 2022 20:25:35 +0000 Received: from pps.filterd (phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (8.17.1.5/8.17.1.5) with ESMTP id 2AAJ9hq9009676; Thu, 10 Nov 2022 20:04:26 GMT Received: from nam04-dm6-obe.outbound.protection.outlook.com (mail-dm6nam04lp2048.outbound.protection.outlook.com [104.47.73.48]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 3kpcq5em02-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 10 Nov 2022 20:04:26 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Ix4K7E/QNjd3McTWCWh+txAvW1fk5NQDfjX+O3EqPTcWtQg2u9U/f7ykEGY0miqK47bEbmeh5DPZ8YnG0+dWP2od8tMrlLWkHIxT6ns8AteqpKsclzhHaYRsXAv7FePOoEMaqlXV8QLGCclyZ4xZp9mkRqZQGRYmfInLcisc1bSgRNtXT1EbTneCIeZDMROswbD1+FLJcjxyYJdI990RJiQ8AbB38wGdIROZW1ZeMIms9CpDfdu3jUK44UgEdZfMQdAiB+iDM1EjYI2meyvLYO5cQ78mRfcsU1L7xzdjkThHhC/70EPYN+dnPWFm7e9NiQVHaoN8wWLvWEkCUc6owQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=4eoowv03BqkL6iv1KoQXDgV5U/jev4KlQOJKxd1WV+E=; b=FNKBHug/noB6GWRHDhOaMk018f9ALWNMMhL+EyLXbjR3d2R/S/vM1FqIUm/1r3kyFa0SSQeKOxqrol3WtUSCf06YnaKSGq8SaDxK+omDuLIwWtE26JbF/Cp5ESv/YC+Qdfi4g6fIkBwv3oPzYV6+FW18htjW5XuW3tWLA7CIF5aMj1ZiiOSATiQOSUVXUckKhk99RLEcPK4NHO+qrjGPrm6e7V9SkwnFUAxtru1jyCRbdmw8naoIQXQ6cIiMawaOvghhknkbBlwSGD5SO9dfxm8TfNsu+93100s7PXAZY17R1UmdqJyE5+LuIEyzl5dnVd58t1W8yVFMHxIxJc9Bgg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=4eoowv03BqkL6iv1KoQXDgV5U/jev4KlQOJKxd1WV+E=; b=C1uTMASCQeu74KLpQt7bjFkOe2tGC0+13s26/5kFm4sMcbcbfECeb7HBdZTvd3Wm49ArUs4FubEuTG6jKz/FZUP4rrfqmc8o+ApPnes5n0oFNkP7EikWDN83kTHYtc2pFGo8YTAxd13KjrPlhIx3Ag5eTbZwXCTfocPC+GMLDtQ= Received: from MN2PR10MB4173.namprd10.prod.outlook.com (2603:10b6:208:1d1::19) by DS7PR10MB5200.namprd10.prod.outlook.com (2603:10b6:5:3a6::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5791.27; Thu, 10 Nov 2022 20:04:23 +0000 Received: from MN2PR10MB4173.namprd10.prod.outlook.com ([fe80::d9a5:dc39:935b:21bf]) by MN2PR10MB4173.namprd10.prod.outlook.com ([fe80::d9a5:dc39:935b:21bf%7]) with mapi id 15.20.5813.013; Thu, 10 Nov 2022 20:04:23 +0000 From: Stephen Brennan To: Amir Goldstein Cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro Subject: Re: [PATCH v3 0/3] fsnotify: fix softlockups iterating over d_subdirs In-Reply-To: References: <20221021010310.29521-1-stephen.s.brennan@oracle.com> <20221028001016.332663-1-stephen.s.brennan@oracle.com> <20221101175144.yu3l5qo5gfwfpatt@quack3> <877d0eh03t.fsf@oracle.com> Date: Thu, 10 Nov 2022 12:04:21 -0800 Message-ID: <87h6z6fuey.fsf@oracle.com> Content-Type: text/plain X-ClientProxiedBy: SA0PR13CA0025.namprd13.prod.outlook.com (2603:10b6:806:130::30) To MN2PR10MB4173.namprd10.prod.outlook.com (2603:10b6:208:1d1::19) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN2PR10MB4173:EE_|DS7PR10MB5200:EE_ X-MS-Office365-Filtering-Correlation-Id: 689339e2-c10a-4738-c632-08dac356c31b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MN2PR10MB4173.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(396003)(366004)(346002)(376002)(136003)(39860400002)(451199015)(41300700001)(2906002)(5660300002)(8936002)(6506007)(6916009)(66476007)(66946007)(54906003)(66556008)(316002)(36756003)(38100700002)(8676002)(4326008)(478600001)(83380400001)(6512007)(186003)(86362001)(26005)(53546011)(6486002)(2616005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?lWXyb0uAm5qQGArr1Bdolqca0BHcGM1c4QQau9ADpNR0kkfXpR/9ZdxkroGw?= =?us-ascii?Q?u3wIXmw/x59tEFZFf/tz7PE0Gu6QNF+79XdmnnD6e0CQpYf40vBqwEGYiIBN?= =?us-ascii?Q?J07QaA9qd1ZhCtTMWGJX1eXUVqUewLlyaO8TSq6QG90F39o02W0ZQBCYUFDN?= =?us-ascii?Q?sNC+Kgl+Ciw5MurLSkiA7rS//rxhlA4o8V5udGcnyFy/3vN1ZFTj9b6WTpSq?= =?us-ascii?Q?Fp79Wu5oJkv3Ifw03eRS/pY9CBFhRnd3OxlJHI5gEO54zz1cCpf8kvSUflyA?= =?us-ascii?Q?E/FWazhLSn7ZeEO3K31JNnTz7ocxcMA2VixGc0+4H8sAgNeV+K5InKgQDK6l?= =?us-ascii?Q?fPl6P3g8wfHvK/QuQwM7gvhNchHdin4jOnbMQb3zEaD4hZkMiWN3iVSF1j/D?= =?us-ascii?Q?6/Rg1T7zXTtKonEZOfb7CExu7cSMzyEdqJkiUBTmYO9xDZ+s5MIq8/r52Vvk?= =?us-ascii?Q?MWrIW0pMRg0gOZqpCTFZIKonXw7JnL8OfMsPliV+Qs1tU1LF/xJTUz6B5lPD?= =?us-ascii?Q?tHqqXvpGYsYs4G/WULu/xUR8tWWKThynxocLndepNTxlTn5t8cHigusXo6xg?= =?us-ascii?Q?qhqQC+0YPql4sMgcEJU9arfGJaedlbt/jGSCBV2iD18E1piAQXpTwbdowBca?= =?us-ascii?Q?URSSV+n3l+pJRKau6MaR4DHy2HzLKjhLikighef1D2BwGGaiW9AsQuyrPsqE?= =?us-ascii?Q?e85ehWkLAxTLw2Sai3hp/cqd0hAASSUdvwh49enBmOnRVwy3ECTNBLwNXSW+?= =?us-ascii?Q?Uq4syox2WZgFokQqeXRKBlJoXTJrr/0glofRmlz7UXdIsJ69C/4SsDA9gFjN?= =?us-ascii?Q?z5O+B8VKF6Zzhhu9N+gU42VGBM5ppqHIaPmqmBMYtEtQBw1lhODy2y18q/uj?= =?us-ascii?Q?gXFkiv/UGPrW+wVJ3UvBON+JhKro+3kSto4WVVKJLx4YtkzSx7eV49oPSj4t?= =?us-ascii?Q?lwXc2kH2Opf5xG5//rUYIictExZoJ1312fL4Ski0lwzFVUA7tmLUIZd9+ehF?= =?us-ascii?Q?eSmWZUOTkm7WxTbScsFfvvtPozuEzHZx5+Ec97RgLp/wUo64hhwDfYkW26W/?= =?us-ascii?Q?aVLeNHsHiQma86FhyIfAaE6rRX6xOaFQkiyusyckn+ZXovqWbdb/641wtLds?= =?us-ascii?Q?cZdzzFYdawSf4XCsCFwR/85BSuVjiFzjwxS9gl9kkuH4R1sHb599TC2PnJ7c?= =?us-ascii?Q?cBodbnzUjrFBs/tN8Pmz/1OAqo6VSBhpT4qCbI37kLYZ42pJsSa/khKaBklK?= =?us-ascii?Q?JujwvrKJ7nKI4soSW/rE4AyxzWq96ddLdBTPuwYP1lWQWe7Pk4ni5Eg5KR4a?= =?us-ascii?Q?KWku5x8LZzqzNgENPIkerF0osteBA9aV919qsizICoYmGKn4Rze3WdeGWEmF?= =?us-ascii?Q?gD5jlrmRGjsgrwOoH9RQ5NZ1WyuqjaRAiH6slEYTiznQHP74K6+a6K9NX9eZ?= =?us-ascii?Q?PicgO9neJ/U7CrUYq62V3rg+TUs35fK2D5AXNBy7ZDCMXmR8IHHgjBYWypYS?= =?us-ascii?Q?+wSQazrPle3gH/Q6Xgeq3scPTXuehGXQYm03bS2nhS5HTKE/lXq/T6/niH7t?= =?us-ascii?Q?VZFrkC0uBLQYSAiVlatILE/+uIb2hhZPxuCaS/m9jSe7mcJUqEdkc1hbXZTA?= =?us-ascii?Q?Gw=3D=3D?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 689339e2-c10a-4738-c632-08dac356c31b X-MS-Exchange-CrossTenant-AuthSource: MN2PR10MB4173.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Nov 2022 20:04:23.6514 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: BZz/AN7TUVTaagMwpgchlI6b/oyFyqx+XL4fIwvZ+fazNk6ztuYjfT+n5RpLtfpb6wyd7+dQBzTvsen8Xka9R+iXZn6tC7bIDS37mz+XuVs= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR10MB5200 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-11-10_12,2022-11-09_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 spamscore=0 adultscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2211100141 X-Proofpoint-GUID: _isaNY94h-ReeHXA_t_ljJFzjq53wzyi X-Proofpoint-ORIG-GUID: _isaNY94h-ReeHXA_t_ljJFzjq53wzyi Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Amir Goldstein writes: [...] > IIUC, patches #1+#3 fix a reproducible softlock, so if Al approves them, > I see no reason to withhold. > > With patches #1+#3 applied, the penalty is restricted to adding or > removing/destroying multiple marks on very large dirs or dirs with > many negative dentries. > > I think that fixing the synthetic test case of multiple added marks > is rather easy even without DCACHE_FSNOTIFY_PARENT_WATCHED. > Something like the attached patch is what Jan had suggested in the > first place. > > The synthetic test case of concurrent add/remove watch on the same > dir may still result in multiple children iterations, but that will usually > not be avoided even with DCACHE_FSNOTIFY_PARENT_WATCHED > and probably not worth optimizing for. > > Thoughts? If I understand your train of thought, your below patch would take the place of my patch #2, since #3 requires we not hold a spinlock during fsnotify_update_children_dentry_flags(). And since you fully rely on dentry accessors to lazily clear flags, you don't need to have the mutual exclusion provided by the inode lock. I like that a lot. However, the one thing I see here is that if we no longer hold the inode lock, patch #3 needs to be re-examined: it assumes that dentries can't be removed or moved around, and that assumption is only true with the inode lock held. I'll test things out with this patch replacing #2 and see how things shake out. Maybe I can improve #3. Thanks, Stephen > > Thanks, > Amir. > From c8ea1d84397c26ce334bff9d9f721400cebb88dd Mon Sep 17 00:00:00 2001 > From: Amir Goldstein > Date: Wed, 2 Nov 2022 10:28:01 +0200 > Subject: [PATCH] fsnotify: clear PARENT_WATCHED flags lazily > > Call fsnotify_update_children_dentry_flags() to set PARENT_WATCHED flags > only when parent starts watching children. > > When parent stops watching children, clear false positive PARENT_WATCHED > flags lazily in __fsnotify_parent() for each accessed child. > > Suggested-by: Jan Kara > Signed-off-by: Amir Goldstein > --- > fs/notify/fsnotify.c | 26 ++++++++++++++++++++------ > fs/notify/fsnotify.h | 3 ++- > fs/notify/mark.c | 32 +++++++++++++++++++++++++++++--- > include/linux/fsnotify_backend.h | 8 +++++--- > 4 files changed, 56 insertions(+), 13 deletions(-) > > diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c > index 1e541a9bd12b..f60078d6bb97 100644 > --- a/fs/notify/fsnotify.c > +++ b/fs/notify/fsnotify.c > @@ -103,17 +103,13 @@ void fsnotify_sb_delete(struct super_block *sb) > * parent cares. Thus when an event happens on a child it can quickly tell > * if there is a need to find a parent and send the event to the parent. > */ > -void __fsnotify_update_child_dentry_flags(struct inode *inode) > +void fsnotify_update_children_dentry_flags(struct inode *inode, bool watched) > { > struct dentry *alias; > - int watched; > > if (!S_ISDIR(inode->i_mode)) > return; > > - /* determine if the children should tell inode about their events */ > - watched = fsnotify_inode_watches_children(inode); > - > spin_lock(&inode->i_lock); > /* run all of the dentries associated with this inode. Since this is a > * directory, there damn well better only be one item on this list */ > @@ -140,6 +136,24 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode) > spin_unlock(&inode->i_lock); > } > > +/* > + * Lazily clear false positive PARENT_WATCHED flag for child whose parent had > + * stopped wacthing children. > + */ > +static void fsnotify_update_child_dentry_flags(struct inode *inode, > + struct dentry *dentry) > +{ > + spin_lock(&dentry->d_lock); > + /* > + * d_lock is a sufficient barrier to prevent observing a non-watched > + * parent state from before the fsnotify_update_children_dentry_flags() > + * or fsnotify_update_flags() call that had set PARENT_WATCHED. > + */ > + if (!fsnotify_inode_watches_children(inode)) > + dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; > + spin_unlock(&dentry->d_lock); > +} > + > /* Are inode/sb/mount interested in parent and name info with this event? */ > static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt, > __u32 mask) > @@ -208,7 +222,7 @@ int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data, > p_inode = parent->d_inode; > p_mask = fsnotify_inode_watches_children(p_inode); > if (unlikely(parent_watched && !p_mask)) > - __fsnotify_update_child_dentry_flags(p_inode); > + fsnotify_update_child_dentry_flags(p_inode, dentry); > > /* > * Include parent/name in notification either if some notification > diff --git a/fs/notify/fsnotify.h b/fs/notify/fsnotify.h > index fde74eb333cc..bce9be36d06b 100644 > --- a/fs/notify/fsnotify.h > +++ b/fs/notify/fsnotify.h > @@ -74,7 +74,8 @@ static inline void fsnotify_clear_marks_by_sb(struct super_block *sb) > * update the dentry->d_flags of all of inode's children to indicate if inode cares > * about events that happen to its children. > */ > -extern void __fsnotify_update_child_dentry_flags(struct inode *inode); > +extern void fsnotify_update_children_dentry_flags(struct inode *inode, > + bool watched); > > extern struct kmem_cache *fsnotify_mark_connector_cachep; > > diff --git a/fs/notify/mark.c b/fs/notify/mark.c > index fcc68b8a40fd..614bce0e7261 100644 > --- a/fs/notify/mark.c > +++ b/fs/notify/mark.c > @@ -176,6 +176,24 @@ static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) > return fsnotify_update_iref(conn, want_iref); > } > > +static bool fsnotify_conn_watches_children( > + struct fsnotify_mark_connector *conn) > +{ > + if (conn->type != FSNOTIFY_OBJ_TYPE_INODE) > + return false; > + > + return fsnotify_inode_watches_children(fsnotify_conn_inode(conn)); > +} > + > +static void fsnotify_conn_set_children_dentry_flags( > + struct fsnotify_mark_connector *conn) > +{ > + if (conn->type != FSNOTIFY_OBJ_TYPE_INODE) > + return; > + > + fsnotify_update_children_dentry_flags(fsnotify_conn_inode(conn), true); > +} > + > /* > * Calculate mask of events for a list of marks. The caller must make sure > * connector and connector->obj cannot disappear under us. Callers achieve > @@ -184,15 +202,23 @@ static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) > */ > void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) > { > + bool update_children; > + > if (!conn) > return; > > spin_lock(&conn->lock); > + update_children = !fsnotify_conn_watches_children(conn); > __fsnotify_recalc_mask(conn); > + update_children &= fsnotify_conn_watches_children(conn); > spin_unlock(&conn->lock); > - if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) > - __fsnotify_update_child_dentry_flags( > - fsnotify_conn_inode(conn)); > + /* > + * Set children's PARENT_WATCHED flags only if parent started watching. > + * When parent stops watching, we clear false positive PARENT_WATCHED > + * flags lazily in __fsnotify_parent(). > + */ > + if (update_children) > + fsnotify_conn_set_children_dentry_flags(conn); > } > > /* Free all connectors queued for freeing once SRCU period ends */ > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > index a31423c376a7..bd90bcf6c3b0 100644 > --- a/include/linux/fsnotify_backend.h > +++ b/include/linux/fsnotify_backend.h > @@ -586,12 +586,14 @@ static inline __u32 fsnotify_parent_needed_mask(__u32 mask) > > static inline int fsnotify_inode_watches_children(struct inode *inode) > { > + __u32 parent_mask = READ_ONCE(inode->i_fsnotify_mask); > + > /* FS_EVENT_ON_CHILD is set if the inode may care */ > - if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD)) > + if (!(parent_mask & FS_EVENT_ON_CHILD)) > return 0; > /* this inode might care about child events, does it care about the > * specific set of events that can happen on a child? */ > - return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD; > + return parent_mask & FS_EVENTS_POSS_ON_CHILD; > } > > /* > @@ -605,7 +607,7 @@ static inline void fsnotify_update_flags(struct dentry *dentry) > /* > * Serialisation of setting PARENT_WATCHED on the dentries is provided > * by d_lock. If inotify_inode_watched changes after we have taken > - * d_lock, the following __fsnotify_update_child_dentry_flags call will > + * d_lock, the following fsnotify_update_children_dentry_flags call will > * find our entry, so it will spin until we complete here, and update > * us with the new state. > */ > -- > 2.25.1