On 2023/8/17 11:52, Jaegeuk Kim wrote:
On Wed, Aug 16, 2023 at 7:11 PM Guenter Roeck <li...@roeck-us.net> wrote:
On Wed, Aug 16, 2023 at 10:25:06AM -0700, Jaegeuk Kim wrote:
Hi,
On Tue, Aug 15, 2023 at 10:09 PM Guenter Roeck <li...@roeck-us.net> wrote:
Hi,
when trying to boot from an f2fs file system with lock debugging enabled,
I get the attached circular locking dependency warning. Is this a known
problem ?
Thanks,
Guenter
---
[ 10.315522] ======================================================
[ 10.315620] WARNING: possible circular locking dependency detected
[ 10.315753] 6.5.0-rc6-00027-g91aa6c412d7f #1 Tainted: G N
[ 10.315843] ------------------------------------------------------
[ 10.315922] seedrng/717 is trying to acquire lock:
[ 10.316010] ffff8e0e02c6b868 (&fi->i_sem){+.+.}-{3:3}, at:
f2fs_add_inline_entry+0x134/0x2d0
[ 10.316315]
[ 10.316315] but task is already holding lock:
[ 10.316391] ffff8e0e02c6b278 (&fi->i_xattr_sem){.+.+}-{3:3}, at:
f2fs_add_dentry+0x41/0xc0
[ 10.316543]
[ 10.316543] which lock already depends on the new lock.
[ 10.316543]
[ 10.316641]
[ 10.316641] the existing dependency chain (in reverse order) is:
[ 10.316745]
[ 10.316745] -> #1 (&fi->i_xattr_sem){.+.+}-{3:3}:
[ 10.316883] down_read+0x3d/0x170
[ 10.316973] f2fs_getxattr+0x370/0x440
[ 10.317036] __f2fs_get_acl+0x38/0x1e0
[ 10.317094] f2fs_init_acl+0x69/0x420
[ 10.317151] f2fs_init_inode_metadata+0x72/0x450
[ 10.317218] f2fs_add_regular_entry+0x372/0x510
[ 10.317283] f2fs_add_dentry+0xb8/0xc0
[ 10.317340] f2fs_do_add_link+0xd9/0x110
[ 10.317399] f2fs_mkdir+0xdf/0x180
[ 10.317453] vfs_mkdir+0x142/0x220
[ 10.317508] do_mkdirat+0x7c/0x120
[ 10.317561] __x64_sys_mkdir+0x47/0x70
[ 10.317617] do_syscall_64+0x3f/0x90
[ 10.317673] entry_SYSCALL_64_after_hwframe+0x73/0xdd
[ 10.317757]
[ 10.317757] -> #0 (&fi->i_sem){+.+.}-{3:3}:
[ 10.317843] __lock_acquire+0x16bf/0x2860
[ 10.317907] lock_acquire+0xcc/0x2c0
[ 10.317962] down_write+0x3a/0xc0
[ 10.318014] f2fs_add_inline_entry+0x134/0x2d0
[ 10.318077] f2fs_add_dentry+0x55/0xc0
[ 10.318141] f2fs_do_add_link+0xd9/0x110
[ 10.318201] f2fs_create+0xe8/0x170
[ 10.318255] lookup_open.isra.0+0x58e/0x6c0
[ 10.318317] path_openat+0x2af/0xa40
[ 10.318372] do_filp_open+0xb1/0x160
[ 10.318428] do_sys_openat2+0x91/0xc0
[ 10.318485] __x64_sys_open+0x54/0xa0
[ 10.318541] do_syscall_64+0x3f/0x90
[ 10.318597] entry_SYSCALL_64_after_hwframe+0x73/0xdd
[ 10.318676]
[ 10.318676] other info that might help us debug this:
[ 10.318676]
[ 10.318799] Possible unsafe locking scenario:
[ 10.318799]
[ 10.318875] CPU0 CPU1
[ 10.318935] ---- ----
[ 10.318999] rlock(&fi->i_xattr_sem);
[ 10.319068] lock(&fi->i_sem);
[ 10.319166] lock(&fi->i_xattr_sem);
[ 10.319264] lock(&fi->i_sem);
It looks like the same one reported by syzbot.
https://syzkaller.appspot.com/bug?extid=a4976ce949df66b1ddf1
However, I suspect it's a false alarm, since I'm interpreting the loop as below.
CPU0 CPU1
lock(new_inode#1->i_xattr_sem)
The call path is as below:
CPU0 CPU1
- f2fs_create
- f2fs_do_add_link
- f2fs_down_read(&F2FS_I(dir)->i_xattr_sem);
lock(dir#1->i_xattr_sem)
- f2fs_mkdir
- f2fs_do_add_link
- f2fs_add_regular_entry
-
f2fs_down_write(&F2FS_I(inode)->i_sem);
lock(new_dir_inode->i_sem)
- f2fs_init_inode_metadata
- __f2fs_get_acl
- f2fs_getxattr
-
f2fs_down_read(&F2FS_I(inode)->i_xattr_sem);
lock(dir#2->i_xattr_sem)
- f2fs_down_write(&F2FS_I(inode)->i_sem);
lock(new_reg_inode->i_sem)
1. i_xattr_sems were from different directories, otherwise, create and
mkdir may race on dir->i_rwsem.
2. fi->i_sems were from different type of inodes, one is regular, and
another is directory.
lock(new_inode#2->i_sem)
lock(dir->i_xattr_sem)
lock(new_inode#1->i_sem)
This looks fine to me.
Based on your feedback, am I correct assuming that you don't plan
to fix this ?
I'm quite open to something that I may miss. Chao, what do you think?
Jaegeuk, I agree with you, it looks like a false alarm.
Thanks,
Thanks,
Guenter
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