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BUG: KCSAN: data-race in has_bh_in_lru / invalidate_bh_lrus_cpu

write to 0xffff888237d42f10 of 8 bytes by task 10539 on cpu 1:
 __invalidate_bh_lrus fs/buffer.c:1393 [inline]
 invalidate_bh_lrus_cpu+0xad/0xe0 fs/buffer.c:1434
 lru_add_drain_cpu+0x243/0x270 mm/swap.c:645
 lru_add_drain+0x28/0x40 mm/swap.c:724
 exit_mmap+0x208/0x460 mm/mmap.c:3196
 __mmput+0x27/0x1c0 kernel/fork.c:1101
 mmput+0x3d/0x50 kernel/fork.c:1122
 exit_mm+0x2f7/0x3f0 kernel/exit.c:501
 do_exit+0x402/0x1530 kernel/exit.c:812
 do_group_exit+0xce/0x1a0 kernel/exit.c:922
 get_signal+0xfa3/0x15e0 kernel/signal.c:2808
 arch_do_signal_or_restart+0x2a/0x220 arch/x86/kernel/signal.c:865
 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+0x109/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237d42f10 of 8 bytes by task 1789 on cpu 0:
 has_bh_in_lru+0x31/0x1c0 fs/buffer.c:1415
 smp_call_function_many_cond+0x226/0x620 kernel/smp.c:915
 on_each_cpu_cond_mask+0x31/0x40 kernel/smp.c:1133
 on_each_cpu_cond include/linux/smp.h:105 [inline]
 invalidate_bh_lrus+0x26/0x30 fs/buffer.c:1424
 invalidate_bdev+0x4b/0x70 fs/block_dev.c:95
 ext4_put_super+0x5d0/0x8c0 fs/ext4/super.c:1240
 generic_shutdown_super+0xe1/0x230 fs/super.c:465
 kill_block_super+0x4a/0x90 fs/super.c:1395
 deactivate_locked_super+0x65/0xd0 fs/super.c:335
 deactivate_super+0x85/0x90 fs/super.c:366
 cleanup_mnt+0x267/0x2d0 fs/namespace.c:1136
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1143
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff8881069cf5b0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1789 Comm: syz-executor.2 Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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