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BUG: KCSAN: data-race in activate_page / lru_add_drain_all

write to 0xffff88812c028cc0 of 1 bytes by task 913 on cpu 0:
 pagevec_add include/linux/pagevec.h:81 [inline]
 activate_page+0x1a4/0x2d0 mm/swap.c:360
 mark_page_accessed+0x20e/0x340 mm/swap.c:442
 zap_pte_range+0x5e6/0x1630 mm/memory.c:1279
 zap_pmd_range mm/memory.c:1386 [inline]
 zap_pud_range mm/memory.c:1415 [inline]
 zap_p4d_range mm/memory.c:1436 [inline]
 unmap_page_range+0x751/0x870 mm/memory.c:1457
 unmap_single_vma+0x157/0x210 mm/memory.c:1502
 unmap_vmas+0xc0/0x150 mm/memory.c:1534
 exit_mmap+0x1c7/0x3b0 mm/mmap.c:3183
 __mmput+0xa2/0x220 kernel/fork.c:1077
 mmput+0x38/0x40 kernel/fork.c:1098
 exit_mm+0x2c8/0x330 kernel/exit.c:483
 do_exit+0x40f/0x16c0 kernel/exit.c:793
 do_group_exit+0xcb/0x180 kernel/exit.c:903
 get_signal+0xe9f/0x1650 kernel/signal.c:2757
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812c028cc0 of 1 bytes by task 8723 on cpu 1:
 pagevec_count include/linux/pagevec.h:68 [inline]
 need_activate_page_drain mm/swap.c:348 [inline]
 lru_add_drain_all+0x20b/0x3b0 mm/swap.c:801
 invalidate_bdev+0x50/0x70 fs/block_dev.c:96
 ext4_put_super+0x5af/0x8f0 fs/ext4/super.c:1075
 generic_shutdown_super+0xde/0x210 fs/super.c:464
 kill_block_super+0x4a/0x90 fs/super.c:1444
 deactivate_locked_super+0x6a/0xb0 fs/super.c:335
 deactivate_super+0x85/0x90 fs/super.c:366
 cleanup_mnt+0x277/0x2e0 fs/namespace.c:1118
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1125
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:165 [inline]
 exit_to_user_mode_prepare+0x1b2/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8723 Comm: syz-executor.4 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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