======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc5-next-20221115 #1 Not tainted
------------------------------------------------------
syz-executor.0/9839 is trying to acquire lock:
ffff8880100943f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: __jbd2_log_wait_for_space+0x238/0x460

but task is already holding lock:
ffff8880440d7150 (&sb->s_type->i_mutex_key#6){++++}-{3:3}, at: ext4_buffered_write_iter+0xb0/0x460

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sb->s_type->i_mutex_key#6){++++}-{3:3}:
       down_read+0x9c/0x450
       ext4_bmap+0x52/0x470
       bmap+0xb0/0x130
       jbd2_journal_bmap+0xac/0x190
       jbd2_journal_flush+0x857/0xc10
       __ext4_ioctl+0x9b0/0x4340
       __x64_sys_ioctl+0x19e/0x210
       do_syscall_64+0x3f/0x90
       entry_SYSCALL_64_after_hwframe+0x72/0xdc

-> #0 (&journal->j_checkpoint_mutex){+.+.}-{3:3}:
       __lock_acquire+0x2a02/0x5e70
       lock_acquire+0x1a6/0x530
       mutex_lock_io_nested+0x14c/0x1330
       __jbd2_log_wait_for_space+0x238/0x460
       add_transaction_credits+0xa42/0xb80
       start_this_handle+0x3ac/0x14c0
       jbd2__journal_start+0x394/0x8d0
       __ext4_journal_start_sb+0x395/0x470
       ext4_dirty_inode+0xa1/0x110
       __mark_inode_dirty+0x1aa/0xe70
       generic_update_time+0x21b/0x2b0
       file_modified_flags+0x2d4/0x330
       ext4_buffered_write_iter+0xf9/0x460
       ext4_file_write_iter+0x3ff/0x1910
       do_iter_readv_writev+0x211/0x3c0
       do_iter_write+0x18b/0x700
       vfs_iter_write+0x74/0xb0
       iter_file_splice_write+0x73e/0xcb0
       direct_splice_actor+0x113/0x180
       splice_direct_to_actor+0x33a/0x8c0
       do_splice_direct+0x1bc/0x290
       do_sendfile+0xb1d/0x1280
       __x64_sys_sendfile64+0x248/0x2a0
       do_syscall_64+0x3f/0x90
       entry_SYSCALL_64_after_hwframe+0x72/0xdc

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#6);
                               lock(&journal->j_checkpoint_mutex);
                               lock(&sb->s_type->i_mutex_key#6);
  lock(&journal->j_checkpoint_mutex);

 *** DEADLOCK ***

2 locks held by syz-executor.0/9839:
 #0: ffff888010090438 (sb_writers#3){.+.+}-{0:0}, at: __x64_sys_sendfile64+0x248/0x2a0
 #1: ffff8880440d7150 (&sb->s_type->i_mutex_key#6){++++}-{3:3}, at: ext4_buffered_write_iter+0xb0/0x460

stack backtrace:
CPU: 0 PID: 9839 Comm: syz-executor.0 Not tainted 6.1.0-rc5-next-20221115 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x8f/0xb7
 check_noncircular+0x263/0x2e0
 __lock_acquire+0x2a02/0x5e70
 lock_acquire+0x1a6/0x530
 mutex_lock_io_nested+0x14c/0x1330
 __jbd2_log_wait_for_space+0x238/0x460
 add_transaction_credits+0xa42/0xb80
 start_this_handle+0x3ac/0x14c0
 jbd2__journal_start+0x394/0x8d0
 __ext4_journal_start_sb+0x395/0x470
 ext4_dirty_inode+0xa1/0x110
 __mark_inode_dirty+0x1aa/0xe70
 generic_update_time+0x21b/0x2b0
 file_modified_flags+0x2d4/0x330
 ext4_buffered_write_iter+0xf9/0x460
 ext4_file_write_iter+0x3ff/0x1910
 do_iter_readv_writev+0x211/0x3c0
 do_iter_write+0x18b/0x700
 vfs_iter_write+0x74/0xb0
 iter_file_splice_write+0x73e/0xcb0
 direct_splice_actor+0x113/0x180
 splice_direct_to_actor+0x33a/0x8c0
 do_splice_direct+0x1bc/0x290
 do_sendfile+0xb1d/0x1280
 __x64_sys_sendfile64+0x248/0x2a0
 do_syscall_64+0x3f/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7f2908fceb19
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2906544188 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f29090e1f60 RCX: 00007f2908fceb19
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000007
RBP: 00007f2909028f6d R08: 0000000000000000 R09: 0000000000000000
R10: 00000000fffffdef R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe6fac5b8f R14: 00007f2906544300 R15: 0000000000022000
 </TASK>