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BUG: KCSAN: data-race in shrink_node / wakeup_kswapd

write to 0xffff88812ffff908 of 4 bytes by task 15634 on cpu 0:
 shrink_node+0x11e3/0x1230 mm/vmscan.c:2853
 shrink_zones+0x2af/0x490 mm/vmscan.c:2971
 do_try_to_free_pages+0x193/0x6e0 mm/vmscan.c:3026
 try_to_free_pages+0x38e/0x8b0 mm/vmscan.c:3265
 __perform_reclaim mm/page_alloc.c:4274 [inline]
 __alloc_pages_direct_reclaim mm/page_alloc.c:4295 [inline]
 __alloc_pages_slowpath+0x55f/0x9e0 mm/page_alloc.c:4699
 __alloc_pages_nodemask+0x266/0x380 mm/page_alloc.c:4915
 alloc_pages_vma+0x3e6/0x890 mm/mempolicy.c:2238
 shmem_alloc_page mm/shmem.c:1565 [inline]
 shmem_alloc_and_acct_page+0x2ba/0x650 mm/shmem.c:1590
 shmem_getpage_gfp+0x669/0x19c0 mm/shmem.c:1886
 shmem_getpage mm/shmem.c:155 [inline]
 shmem_write_begin+0x83/0x100 mm/shmem.c:2523
 generic_perform_write+0x196/0x390 mm/filemap.c:3505
 __generic_file_write_iter+0x154/0x330 mm/filemap.c:3634
 generic_file_write_iter+0x2f3/0x3e0 mm/filemap.c:3666
 call_write_iter include/linux/fs.h:1882 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x665/0x6f0 fs/read_write.c:586
 ksys_pwrite64 fs/read_write.c:693 [inline]
 __do_sys_pwrite64 fs/read_write.c:703 [inline]
 __se_sys_pwrite64 fs/read_write.c:700 [inline]
 __x64_sys_pwrite64+0xf5/0x150 fs/read_write.c:700
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812ffff908 of 4 bytes by task 15631 on cpu 1:
 wakeup_kswapd+0x117/0x480 mm/vmscan.c:3969
 wake_all_kswapds mm/page_alloc.c:4328 [inline]
 __alloc_pages_slowpath+0x1d8/0x9e0 mm/page_alloc.c:4600
 __alloc_pages_nodemask+0x266/0x380 mm/page_alloc.c:4915
 alloc_pages_vma+0x3e6/0x890 mm/mempolicy.c:2238
 alloc_zeroed_user_highpage_movable include/linux/highmem.h:277 [inline]
 do_anonymous_page+0x206/0xf40 mm/memory.c:3516
 handle_pte_fault mm/memory.c:4365 [inline]
 __handle_mm_fault mm/memory.c:4502 [inline]
 handle_mm_fault+0x14fd/0x1af0 mm/memory.c:4600
 faultin_page mm/gup.c:878 [inline]
 __get_user_pages+0xa3d/0x1010 mm/gup.c:1090
 populate_vma_page_range mm/gup.c:1423 [inline]
 __mm_populate+0x24d/0x340 mm/gup.c:1471
 mm_populate include/linux/mm.h:2566 [inline]
 __do_sys_mlockall mm/mlock.c:828 [inline]
 __se_sys_mlockall+0x256/0x280 mm/mlock.c:804
 __x64_sys_mlockall+0x1b/0x20 mm/mlock.c:804
 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: 15631 Comm: syz-executor.2 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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