From: Baokun Li libaokun1@huawei.com
[ Upstream commit 0f28be64d132aaf95d06375c8002ad9ecea69d71 ]
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: <TASK> 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.
Suggested-by: Al Viro viro@zeniv.linux.org.uk Fixes: a9849560c55e ("erofs: introduce a pseudo mnt to manage shared cookies") Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-and-tested-by: Jingbo Xu jefflexu@linux.alibaba.com Reviewed-by: Yang Erkun yangerkun@huawei.com Link: https://lore.kernel.org/r/20240307101018.2021925-1-libaokun1@huawei.com Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 1052f75d1dfae..afc37c9029ce7 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 <linux/pseudo_fs.h> #include <linux/fscache.h> #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 b0409badb0172..410f5af623540 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 3789d62245136..8a82d5cec16da 100644 --- a/fs/erofs/super.c +++ b/fs/erofs/super.c @@ -573,13 +573,6 @@ 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; @@ -706,11 +699,6 @@ 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; @@ -783,20 +771,10 @@ 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; @@ -818,12 +796,6 @@ 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 @@ -862,7 +834,7 @@ 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,