warning: checkpointing journal with EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT can be slow
======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc2-next-20220825 #1 Not tainted
------------------------------------------------------
syz-executor.2/47731 is trying to acquire lock:
ffff88800c9c0400 (&sb->s_type->i_mutex_key#6){++++}-{3:3}, at: ext4_bmap+0x4e/0x470

but task is already holding lock:
ffff88800ff6e3f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: jbd2_journal_flush+0x48b/0xc00

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&journal->j_checkpoint_mutex){+.+.}-{3:3}:
       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_update_time+0x26b/0x410
       file_update_time+0x22b/0x280
       ext4_page_mkwrite+0x2ea/0x1a70
       do_page_mkwrite+0x1a0/0x4f0
       __handle_mm_fault+0x12ac/0x34c0
       handle_mm_fault+0x2e6/0xa20
       do_user_addr_fault+0x536/0x1300
       exc_page_fault+0x98/0x1a0
       asm_exc_page_fault+0x22/0x30

-> #2 (sb_pagefaults){.+.+}-{0:0}:
       ext4_page_mkwrite+0x1f8/0x1a70
       do_page_mkwrite+0x1a0/0x4f0
       __handle_mm_fault+0x12ac/0x34c0
       handle_mm_fault+0x2e6/0xa20
       do_user_addr_fault+0x536/0x1300
       exc_page_fault+0x98/0x1a0
       asm_exc_page_fault+0x22/0x30

-> #1 (&mm->mmap_lock#2){++++}-{3:3}:
       internal_get_user_pages_fast+0x133a/0x2ec0
       get_user_pages_fast+0x66/0xa0
       __iov_iter_get_pages_alloc+0x38d/0x2290
       iov_iter_get_pages2+0xa4/0x100
       bio_iov_iter_get_pages+0x1da/0x10b0
       iomap_dio_bio_iter+0x92f/0x1510
       __iomap_dio_rw+0xe14/0x1bd0
       iomap_dio_rw+0x3c/0xa0
       ext4_file_write_iter+0xa96/0x1820
       vfs_write+0x9c3/0xd90
       __x64_sys_pwrite64+0x1fb/0x260
       do_syscall_64+0x3b/0x90
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&sb->s_type->i_mutex_key#6){++++}-{3:3}:
       __lock_acquire+0x2a02/0x5e70
       lock_acquire+0x1a2/0x530
       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

other info that might help us debug this:

Chain exists of:
  &sb->s_type->i_mutex_key#6 --> sb_pagefaults --> &journal->j_checkpoint_mutex

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

2 locks held by syz-executor.2/47731:
 #0: ffff88800ff6e170 (&journal->j_barrier){+.+.}-{3:3}, at: jbd2_journal_lock_updates+0x15e/0x310
 #1: ffff88800ff6e3f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: jbd2_journal_flush+0x48b/0xc00

stack backtrace:
CPU: 0 PID: 47731 Comm: syz-executor.2 Not tainted 6.0.0-rc2-next-20220825 #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
 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
RIP: 0033:0x7f20b271cb19
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:00007f20afc71188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f20b2830020 RCX: 00007f20b271cb19
RDX: 0000000020000340 RSI: 000000004004662b RDI: 0000000000000004
RBP: 00007f20b2776f6d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff82b35d8f R14: 00007f20afc71300 R15: 0000000000022000
 </TASK>
warning: checkpointing journal with EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT can be slow
warning: checkpointing journal with EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT can be slow
cgroup: fork rejected by pids controller in /syz2
warning: checkpointing journal with EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT can be slow
syz-executor.3 (48626) used greatest stack depth: 22616 bytes left
loop6: detected capacity change from 0 to 40