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Thu, 7 Mar 2024 19:19:26 +0800 Message-ID: Date: Thu, 7 Mar 2024 19:19:25 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2] erofs: fix lockdep false positives on initializing erofs_pseudo_mnt To: Baokun Li , References: <20240307101018.2021925-1-libaokun1@huawei.com> In-Reply-To: <20240307101018.2021925-1-libaokun1@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.210] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemd200008.china.huawei.com (7.221.188.40) X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: yangerkun via Linux-erofs Reply-To: yangerkun Cc: brauner@kernel.org, linux-kernel@vger.kernel.org, huyue2@coolpad.com, viro@zeniv.linux.org.uk, yukuai3@huawei.com, chengzhihao1@huawei.com Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" LGTM Reviewed-by: Yang Erkun 在 2024/3/7 18:10, Baokun Li 写道: > Lockdep reported the following issue when mounting erofs with a domain_id: > > ============================================ > WARNING: possible recursive locking detected > 6.8.0-rc7-xfstests #521 Not tainted > -------------------------------------------- > 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" > > @@ -12,6 +13,18 @@ static LIST_HEAD(erofs_domain_list); > static LIST_HEAD(erofs_domain_cookies_list); > static struct vfsmount *erofs_pseudo_mnt; > > +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 = { > + .owner = THIS_MODULE, > + .name = "pseudo_erofs", > + .init_fs_context = erofs_anon_init_fs_context, > + .kill_sb = 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; > > if (!erofs_pseudo_mnt) { > - struct vfsmount *mnt = kern_mount(&erofs_fs_type); > + struct vfsmount *mnt = kern_mount(&erofs_anon_fs_type); > if (IS_ERR(mnt)) { > err = 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; > }; > > -extern struct file_system_type erofs_fs_type; > extern const struct super_operations erofs_sops; > > 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 = { > .get_parent = erofs_get_parent, > }; > > -static int erofs_fc_fill_pseudo_super(struct super_block *sb, struct fs_context *fc) > -{ > - static const struct tree_descr empty_descr = {""}; > - > - 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; > } > > -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 = fc->fs_private; > @@ -789,20 +777,10 @@ static const struct fs_context_operations erofs_context_ops = { > .free = erofs_fc_free, > }; > > -static const struct fs_context_operations erofs_anon_context_ops = { > - .get_tree = erofs_fc_anon_get_tree, > -}; > - > static int erofs_init_fs_context(struct fs_context *fc) > { > struct erofs_fs_context *ctx; > > - /* pseudo mount for anon inodes */ > - if (fc->sb_flags & SB_KERNMOUNT) { > - fc->ops = &erofs_anon_context_ops; > - return 0; > - } > - > ctx = 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; > > - /* 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); > } > > -struct file_system_type erofs_fs_type = { > +static struct file_system_type erofs_fs_type = { > .owner = THIS_MODULE, > .name = "erofs", > .init_fs_context = erofs_init_fs_context,