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erofs: fix lockdep false positives on initializing erofs_pseudo_mnt 

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: a9849560c5 ("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>
This commit is contained in:
Baokun Li 2024-03-07 18:10:18 +08:00 committed by Gao Xiang
parent 706fd68fce
commit 0f28be64d1
3 changed files with 15 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
fs/erofs/fscache.c
View File

@ -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;

1
fs/erofs/internal.h
View File

@ -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;

30
fs/erofs/super.c
View File

@ -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,