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BUG: KCSAN: data-race in __jbd2_journal_drop_transaction / start_this_handle

write to 0xffff888103678878 of 8 bytes by task 28846 on cpu 0:
 jbd2_get_transaction fs/jbd2/transaction.c:125 [inline]
 start_this_handle+0xd37/0x1050 fs/jbd2/transaction.c:416
 jbd2__journal_start+0x1fc/0x3f0 fs/jbd2/transaction.c:525
 __ext4_journal_start_sb+0x159/0x310 fs/ext4/ext4_jbd2.c:105
 __ext4_journal_start fs/ext4/ext4_jbd2.h:326 [inline]
 ext4_dirty_inode+0x58/0xa0 fs/ext4/inode.c:5905
 __mark_inode_dirty+0x72/0x6c0 fs/fs-writeback.c:2399
 generic_update_time fs/inode.c:1784 [inline]
 inode_update_time+0x1b4/0x1d0 fs/inode.c:1797
 file_update_time+0x1f3/0x230 fs/inode.c:2014
 file_modified+0x62/0x80 fs/inode.c:2037
 ext4_write_checks fs/ext4/file.c:247 [inline]
 ext4_buffered_write_iter+0x1f2/0x380 fs/ext4/file.c:264
 ext4_file_write_iter+0x2e7/0x1200
 __kernel_write+0x32e/0x5e0 fs/read_write.c:535
 do_acct_process+0xb4d/0xd40 kernel/acct.c:518
 slow_acct_process kernel/acct.c:577 [inline]
 acct_process+0x1ad/0x250 kernel/acct.c:601
 do_exit+0x612/0x17a0 kernel/exit.c:822
 do_group_exit+0xce/0x180 kernel/exit.c:929
 get_signal+0xf83/0x1510 kernel/signal.c:2820
 arch_do_signal_or_restart+0x8c/0x2e0 arch/x86/kernel/signal.c:868
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x113/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xd0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888103678878 of 8 bytes by task 1404 on cpu 1:
 __jbd2_journal_drop_transaction+0x1f0/0x2f0 fs/jbd2/checkpoint.c:803
 __jbd2_journal_remove_checkpoint+0x2d5/0x3a0 fs/jbd2/checkpoint.c:734
 jbd2_journal_commit_transaction+0x23f1/0x3460 fs/jbd2/commit.c:1019
 kjournald2+0x263/0x480 fs/jbd2/journal.c:213
 kthread+0x2c7/0x2e0 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30

value changed: 0x0000000000000000 -> 0xffff8881392c9800

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1404 Comm: jbd2/sda1-8 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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