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BUG: KCSAN: data-race in mm_update_next_owner / stop_this_handle

write to 0xffff888139c4802c of 4 bytes by task 10729 on cpu 1:
 memalloc_nofs_restore include/linux/sched/mm.h:258 [inline]
 stop_this_handle+0x2ae/0x2f0 fs/jbd2/transaction.c:744
 jbd2_journal_stop+0x573/0x6d0 fs/jbd2/transaction.c:1907
 __ext4_journal_stop+0x99/0x110 fs/ext4/ext4_jbd2.c:127
 ext4_symlink+0x554/0x780 fs/ext4/namei.c:3419
 vfs_symlink+0xbe/0x170 fs/namei.c:4176
 do_symlinkat+0x11e/0x2b0 fs/namei.c:4206
 __do_sys_symlink fs/namei.c:4227 [inline]
 __se_sys_symlink fs/namei.c:4225 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4225
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888139c4802c of 4 bytes by task 10730 on cpu 0:
 mm_update_next_owner+0x1d9/0x4e0 kernel/exit.c:388
 exit_mm+0x33c/0x430 kernel/exit.c:500
 do_exit+0x3ff/0x1670 kernel/exit.c:812
 do_group_exit+0x17d/0x180 kernel/exit.c:922
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:933
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:931
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:931
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10730 Comm: syz-executor.1 Not tainted 5.12.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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