======================================================
WARNING: possible circular locking dependency detected
5.15.161-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/6234 is trying to acquire lock:
ffff88814b5aa3f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: __jbd2_log_wait_for_space+0x213/0x760 fs/jbd2/checkpoint.c:71

but task is already holding lock:
ffff888059b8f198 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
ffff888059b8f198 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: vfs_unlink+0xe0/0x5f0 fs/namei.c:4269

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sb->s_type->i_mutex_key#9){++++}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_read+0x45/0x2e0 kernel/locking/rwsem.c:1498
       inode_lock_shared include/linux/fs.h:799 [inline]
       ext4_bmap+0x4b/0x410 fs/ext4/inode.c:3152
       bmap+0xa1/0xd0 fs/inode.c:1756
       jbd2_journal_bmap fs/jbd2/journal.c:980 [inline]
       __jbd2_journal_erase fs/jbd2/journal.c:1790 [inline]
       jbd2_journal_flush+0x7a2/0xc90 fs/jbd2/journal.c:2496
       ext4_ioctl_checkpoint fs/ext4/ioctl.c:849 [inline]
       __ext4_ioctl fs/ext4/ioctl.c:1267 [inline]
       ext4_ioctl+0x3249/0x5b80 fs/ext4/ioctl.c:1276
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&journal->j_checkpoint_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
       mutex_lock_io_nested+0x45/0x60 kernel/locking/mutex.c:777
       __jbd2_log_wait_for_space+0x213/0x760 fs/jbd2/checkpoint.c:71
       add_transaction_credits+0x950/0xc00 fs/jbd2/transaction.c:299
       start_this_handle+0x747/0x1570 fs/jbd2/transaction.c:423
       jbd2__journal_start+0x2d1/0x5c0 fs/jbd2/transaction.c:521
       __ext4_journal_start_sb+0x175/0x370 fs/ext4/ext4_jbd2.c:105
       __ext4_journal_start fs/ext4/ext4_jbd2.h:326 [inline]
       __ext4_unlink+0x3a7/0xae0 fs/ext4/namei.c:3265
       ext4_unlink+0x1a9/0x530 fs/ext4/namei.c:3324
       vfs_unlink+0x359/0x5f0 fs/namei.c:4280
       do_unlinkat+0x4a3/0x950 fs/namei.c:4348
       __do_sys_unlink fs/namei.c:4396 [inline]
       __se_sys_unlink fs/namei.c:4394 [inline]
       __x64_sys_unlink+0x45/0x50 fs/namei.c:4394
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#9);
                               lock(&journal->j_checkpoint_mutex);
                               lock(&sb->s_type->i_mutex_key#9);
  lock(&journal->j_checkpoint_mutex);

 *** DEADLOCK ***

3 locks held by syz-executor.4/6234:
 #0: ffff88814b5a6460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377
 #1: ffff88805540e7a0 (&type->i_mutex_dir_key#4/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:824 [inline]
 #1: ffff88805540e7a0 (&type->i_mutex_dir_key#4/1){+.+.}-{3:3}, at: do_unlinkat+0x266/0x950 fs/namei.c:4331
 #2: ffff888059b8f198 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
 #2: ffff888059b8f198 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: vfs_unlink+0xe0/0x5f0 fs/namei.c:4269

stack backtrace:
CPU: 1 PID: 6234 Comm: syz-executor.4 Not tainted 5.15.161-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788