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BUG: KCSAN: data-race in has_bh_in_lru / invalidate_bh_lrus_cpu

write to 0xffff888237d22f18 of 8 bytes by task 27301 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+0x256/0x280 mm/swap.c:623
 lru_add_drain+0x28/0x40 mm/swap.c:702
 exit_mmap+0x218/0x470 mm/mmap.c:3166
 __mmput+0x27/0x1d0 kernel/fork.c:1115
 mmput+0x3d/0x50 kernel/fork.c:1136
 exit_mm+0x2ec/0x3e0 kernel/exit.c:501
 do_exit+0x3ef/0x14a0 kernel/exit.c:812
 do_group_exit+0xa4/0x1a0 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_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237d22f18 of 8 bytes by task 1137 on cpu 0:
 has_bh_in_lru+0x31/0x1c0 fs/buffer.c:1415
 smp_call_function_many_cond+0x236/0x620 kernel/smp.c:917
 on_each_cpu_cond_mask+0x31/0x40 kernel/smp.c:1135
 on_each_cpu_cond include/linux/smp.h:105 [inline]
 invalidate_bh_lrus+0x26/0x30 fs/buffer.c:1424
 kill_bdev fs/block_dev.c:86 [inline]
 blkdev_flush_mapping+0xd4/0x240 fs/block_dev.c:1069
 blkdev_put_whole fs/block_dev.c:1100 [inline]
 blkdev_put+0x3ab/0x4c0 fs/block_dev.c:1393
 kill_block_super+0x7b/0x90 fs/super.c:1398
 deactivate_locked_super+0x65/0xd0 fs/super.c:335
 deactivate_super+0x85/0x90 fs/super.c:366
 cleanup_mnt+0x267/0x2d0 fs/namespace.c:1137
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1144
 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+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff888101369f08 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1137 Comm: syz-executor.0 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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