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BUG: KCSAN: data-race in __ext4_journal_start_sb / jbd2_journal_update_sb_log_tail

write to 0xffff88810254d000 of 8 bytes by task 4853 on cpu 0:
 jbd2_journal_update_sb_log_tail+0x134/0x170 fs/jbd2/journal.c:1637
 jbd2_journal_commit_transaction+0x1c3/0x32b0 fs/jbd2/commit.c:430
 kjournald2+0x263/0x480 fs/jbd2/journal.c:213
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff88810254d000 of 8 bytes by task 30942 on cpu 1:
 is_journal_aborted include/linux/jbd2.h:1647 [inline]
 ext4_journal_check_start fs/ext4/ext4_jbd2.c:82 [inline]
 __ext4_journal_start_sb+0xed/0x310 fs/ext4/ext4_jbd2.c:98
 __ext4_journal_start fs/ext4/ext4_jbd2.h:320 [inline]
 ext4_ext_migrate+0x201/0x1ab0 fs/ext4/migrate.c:444
 ext4_ioctl_setflags+0x7b6/0x7d0 fs/ext4/ioctl.c:449
 __ext4_ioctl fs/ext4/ioctl.c:859 [inline]
 ext4_ioctl+0x209f/0x3560 fs/ext4/ioctl.c:1322
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30942 Comm: syz-executor.4 Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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