loop4: detected capacity change from 0 to 39
======================================================
WARNING: possible circular locking dependency detected
5.19.0-next-20220805 #1 Not tainted
------------------------------------------------------
syz-executor.0/11739 is trying to acquire lock:
ffff88800ff463f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: __jbd2_log_wait_for_space+0x234/0x460

but task is already holding lock:
ffff88804768b5b0 (&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+0x98/0x450
       ext4_bmap+0x4e/0x470
       bmap+0xac/0x120
       jbd2_journal_bmap+0xa8/0x180
       jbd2_journal_flush+0x853/0xc00
       __ext4_ioctl+0x9e9/0x4090
       __x64_sys_ioctl+0x19a/0x210
       do_syscall_64+0x3b/0x90
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&journal->j_checkpoint_mutex){+.+.}-{3:3}:
       __lock_acquire+0x2a02/0x5e70
       lock_acquire+0x1a2/0x530
       mutex_lock_io_nested+0x148/0x1310
       __jbd2_log_wait_for_space+0x234/0x460
       add_transaction_credits+0xa42/0xb80
       start_this_handle+0x3ac/0x14c0
       jbd2__journal_start+0x390/0x8d0
       __ext4_journal_start_sb+0x391/0x470
       ext4_dirty_inode+0x9d/0x110
       __mark_inode_dirty+0x455/0xf00
       generic_write_end+0x315/0x3d0
       ext4_da_write_end+0x15e/0x930
       generic_perform_write+0x308/0x570
       ext4_buffered_write_iter+0x164/0x460
       ext4_file_write_iter+0x3d5/0x1820
       do_iter_readv_writev+0x211/0x3c0
       do_iter_write+0x18b/0x700
       vfs_iter_write+0x70/0xa0
       iter_file_splice_write+0x73a/0xca0
       direct_splice_actor+0x10f/0x170
       splice_direct_to_actor+0x336/0x8c0
       do_splice_direct+0x1b8/0x290
       do_sendfile+0xb1d/0x1280
       __x64_sys_sendfile64+0x1d1/0x210
       do_syscall_64+0x3b/0x90
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

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.0/11739:
 #0: ffff88800ff42438 (sb_writers#3){.+.+}-{0:0}, at: __x64_sys_sendfile64+0x1d1/0x210
 #1: ffff88804768b5b0 (&sb->s_type->i_mutex_key#6){++++}-{3:3}, at: ext4_buffered_write_iter+0xb0/0x460

stack backtrace:
CPU: 1 PID: 11739 Comm: syz-executor.0 Not tainted 5.19.0-next-20220805 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x8b/0xb3
 check_noncircular+0x263/0x2e0
 __lock_acquire+0x2a02/0x5e70
 lock_acquire+0x1a2/0x530
 mutex_lock_io_nested+0x148/0x1310
 __jbd2_log_wait_for_space+0x234/0x460
 add_transaction_credits+0xa42/0xb80
 start_this_handle+0x3ac/0x14c0
 jbd2__journal_start+0x390/0x8d0
 __ext4_journal_start_sb+0x391/0x470
 ext4_dirty_inode+0x9d/0x110
 __mark_inode_dirty+0x455/0xf00
 generic_write_end+0x315/0x3d0
 ext4_da_write_end+0x15e/0x930
 generic_perform_write+0x308/0x570
 ext4_buffered_write_iter+0x164/0x460
 ext4_file_write_iter+0x3d5/0x1820
 do_iter_readv_writev+0x211/0x3c0
 do_iter_write+0x18b/0x700
 vfs_iter_write+0x70/0xa0
 iter_file_splice_write+0x73a/0xca0
 direct_splice_actor+0x10f/0x170
 splice_direct_to_actor+0x336/0x8c0
 do_splice_direct+0x1b8/0x290
 do_sendfile+0xb1d/0x1280
 __x64_sys_sendfile64+0x1d1/0x210
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9affb84b19
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:00007f9afd0fa188 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f9affc97f60 RCX: 00007f9affb84b19
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000003
RBP: 00007f9affbdef6d R08: 0000000000000000 R09: 0000000000000000
R10: 000000007fffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd8761f9ef R14: 00007f9afd0fa300 R15: 0000000000022000
 </TASK>