From nobody Sat Feb 7 23:52:56 2026 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DC4DC83CBB for ; Thu, 7 Mar 2024 10:08:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.187 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709806130; cv=none; b=Te7tLeElunD0wO9n8qgCcSfTwW5Z49vioXoidyWIdDplyHVFWHabgvwdUmDbor82bsQhqf+TwL4++CH8diajCWvE4uUQWhlwJdWx+DLk1n8dm7Gta5wcPUFezNgwshNAaSrGZaPg94YHzh8pq2Qb9RZ6T/5uCpr1wKz8uSBDqr0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709806130; c=relaxed/simple; bh=Whn5ZLyLq1DOG3TJgmxyixKav0+Ndf9qDu+kdSelk7M=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=kJIESUb5eUmsQXcLHBia20Ari3tklmEgnzqItiBtqLZOcqNli4HpviKM8WxVCaKeux9T8vjHCwkVVvI/wwrCRD9iVClpgNucdcSe6qZD3FS/JJt0FS1w7Jzt/PyjAOtJOsLUguwXCtNmasz4E39YfNRwwcdTSKsi3j/ppHO0emI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Tr4hj3HLVzsX8w; Thu, 7 Mar 2024 18:06:45 +0800 (CST) Received: from dggpeml500021.china.huawei.com (unknown [7.185.36.21]) by mail.maildlp.com (Postfix) with ESMTPS id 98A4D140F52; Thu, 7 Mar 2024 18:08:44 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Thu, 7 Mar 2024 18:08:43 +0800 From: Baokun Li To: CC: , , , , , , , , , , , Subject: [PATCH v2] erofs: fix lockdep false positives on initializing erofs_pseudo_mnt Date: Thu, 7 Mar 2024 18:10:18 +0800 Message-ID: <20240307101018.2021925-1-libaokun1@huawei.com> X-Mailer: git-send-email 2.31.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpeml500021.china.huawei.com (7.185.36.21) Content-Type: text/plain; charset="utf-8" Lockdep reported the following issue when mounting erofs with a domain_id: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D WARNING: possible recursive locking detected 6.8.0-rc7-xfstests #521 Not tainted Reviewed-by: Yang Erkun Suggested-by: Al Viro -------------------------------------------- mount/396 is trying to acquire lock: ffff907a8aaaa0e0 (&type->s_umount_key#50/1){+.+.}-{3:3}, at: alloc_super+0xe3/0x3d0 but task is already holding lock: ffff907a8aaa90e0 (&type->s_umount_key#50/1){+.+.}-{3:3}, at: alloc_super+0xe3/0x3d0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&type->s_umount_key#50/1); lock(&type->s_umount_key#50/1); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by mount/396: #0: ffff907a8aaa90e0 (&type->s_umount_key#50/1){+.+.}-{3:3}, at: alloc_super+0xe3/0x3d0 #1: ffffffffc00e6f28 (erofs_domain_list_lock){+.+.}-{3:3}, at: erofs_fscache_register_fs+0x3d/0x270 [erofs] stack backtrace: CPU: 1 PID: 396 Comm: mount Not tainted 6.8.0-rc7-xfstests #521 Call Trace: dump_stack_lvl+0x64/0xb0 validate_chain+0x5c4/0xa00 __lock_acquire+0x6a9/0xd50 lock_acquire+0xcd/0x2b0 down_write_nested+0x45/0xd0 alloc_super+0xe3/0x3d0 sget_fc+0x62/0x2f0 vfs_get_super+0x21/0x90 vfs_get_tree+0x2c/0xf0 fc_mount+0x12/0x40 vfs_kern_mount.part.0+0x75/0x90 kern_mount+0x24/0x40 erofs_fscache_register_fs+0x1ef/0x270 [erofs] erofs_fc_fill_super+0x213/0x380 [erofs] This is because the file_system_type of both erofs and the pseudo-mount point of domain_id is erofs_fs_type, so two successive calls to alloc_super() are considered to be using the same lock and trigger the warning above. Therefore add a nodev file_system_type called erofs_anon_fs_type in fscache.c to silence this complaint. Because kern_mount() takes a pointer to struct file_system_type, not its (string) name. So we don't need to call register_filesystem(). In addition, call init_pseudo() in erofs_anon_init_fs_context() as suggested by Al Viro, so that we can remove erofs_fc_fill_pseudo_super(), erofs_fc_anon_get_tree(), and erofs_anon_context_ops. Signed-off-by: Baokun Li --- V1->V2: Modified as suggested by Al Viro to simplify the code. fs/erofs/fscache.c | 15 ++++++++++++++- fs/erofs/internal.h | 1 - fs/erofs/super.c | 30 +----------------------------- 3 files changed, 15 insertions(+), 31 deletions(-) diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c index 89a7c2453aae..122a4753ecea 100644 --- a/fs/erofs/fscache.c +++ b/fs/erofs/fscache.c @@ -3,6 +3,7 @@ * Copyright (C) 2022, Alibaba Cloud * Copyright (C) 2022, Bytedance Inc. All rights reserved. */ +#include #include #include "internal.h" =20 @@ -12,6 +13,18 @@ static LIST_HEAD(erofs_domain_list); static LIST_HEAD(erofs_domain_cookies_list); static struct vfsmount *erofs_pseudo_mnt; =20 +static int erofs_anon_init_fs_context(struct fs_context *fc) +{ + return init_pseudo(fc, EROFS_SUPER_MAGIC) ? 0 : -ENOMEM; +} + +static struct file_system_type erofs_anon_fs_type =3D { + .owner =3D THIS_MODULE, + .name =3D "pseudo_erofs", + .init_fs_context =3D erofs_anon_init_fs_context, + .kill_sb =3D kill_anon_super, +}; + struct erofs_fscache_request { struct erofs_fscache_request *primary; struct netfs_cache_resources cache_resources; @@ -381,7 +394,7 @@ static int erofs_fscache_init_domain(struct super_block= *sb) goto out; =20 if (!erofs_pseudo_mnt) { - struct vfsmount *mnt =3D kern_mount(&erofs_fs_type); + struct vfsmount *mnt =3D kern_mount(&erofs_anon_fs_type); if (IS_ERR(mnt)) { err =3D PTR_ERR(mnt); goto out; diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h index 0f0706325b7b..701d4eec693a 100644 --- a/fs/erofs/internal.h +++ b/fs/erofs/internal.h @@ -385,7 +385,6 @@ struct erofs_map_dev { unsigned int m_deviceid; }; =20 -extern struct file_system_type erofs_fs_type; extern const struct super_operations erofs_sops; =20 extern const struct address_space_operations erofs_raw_access_aops; diff --git a/fs/erofs/super.c b/fs/erofs/super.c index 9b4b66dcdd4f..6fbb1fba2d31 100644 --- a/fs/erofs/super.c +++ b/fs/erofs/super.c @@ -579,13 +579,6 @@ static const struct export_operations erofs_export_ops= =3D { .get_parent =3D erofs_get_parent, }; =20 -static int erofs_fc_fill_pseudo_super(struct super_block *sb, struct fs_co= ntext *fc) -{ - static const struct tree_descr empty_descr =3D {""}; - - return simple_fill_super(sb, EROFS_SUPER_MAGIC, &empty_descr); -} - static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *= fc) { struct inode *inode; @@ -712,11 +705,6 @@ static int erofs_fc_fill_super(struct super_block *sb,= struct fs_context *fc) return 0; } =20 -static int erofs_fc_anon_get_tree(struct fs_context *fc) -{ - return get_tree_nodev(fc, erofs_fc_fill_pseudo_super); -} - static int erofs_fc_get_tree(struct fs_context *fc) { struct erofs_fs_context *ctx =3D fc->fs_private; @@ -789,20 +777,10 @@ static const struct fs_context_operations erofs_conte= xt_ops =3D { .free =3D erofs_fc_free, }; =20 -static const struct fs_context_operations erofs_anon_context_ops =3D { - .get_tree =3D erofs_fc_anon_get_tree, -}; - static int erofs_init_fs_context(struct fs_context *fc) { struct erofs_fs_context *ctx; =20 - /* pseudo mount for anon inodes */ - if (fc->sb_flags & SB_KERNMOUNT) { - fc->ops =3D &erofs_anon_context_ops; - return 0; - } - ctx =3D kzalloc(sizeof(*ctx), GFP_KERNEL); if (!ctx) return -ENOMEM; @@ -824,12 +802,6 @@ static void erofs_kill_sb(struct super_block *sb) { struct erofs_sb_info *sbi; =20 - /* pseudo mount for anon inodes */ - if (sb->s_flags & SB_KERNMOUNT) { - kill_anon_super(sb); - return; - } - if (erofs_is_fscache_mode(sb)) kill_anon_super(sb); else @@ -868,7 +840,7 @@ static void erofs_put_super(struct super_block *sb) erofs_fscache_unregister_fs(sb); } =20 -struct file_system_type erofs_fs_type =3D { +static struct file_system_type erofs_fs_type =3D { .owner =3D THIS_MODULE, .name =3D "erofs", .init_fs_context =3D erofs_init_fs_context, --=20 2.31.1