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BUG: KCSAN: data-race in snapshot_refaults / snapshot_refaults

write to 0xffff88821851a478 of 8 bytes by task 7898 on cpu 0:
 snapshot_refaults+0x170/0x200 mm/vmscan.c:3046
 do_try_to_free_pages+0x6e8/0x940 mm/vmscan.c:3105
 try_to_free_mem_cgroup_pages+0x1fd/0x4c0 mm/vmscan.c:3383
 reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349
 mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430
 tracehook_notify_resume include/linux/tracehook.h:197 [inline]
 exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
 swapgs_restore_regs_and_return_to_usermode+0x0/0x40

write to 0xffff88821851a478 of 8 bytes by task 30620 on cpu 1:
 snapshot_refaults+0x170/0x200 mm/vmscan.c:3046
 do_try_to_free_pages+0x6e8/0x940 mm/vmscan.c:3105
 try_to_free_mem_cgroup_pages+0x1fd/0x4c0 mm/vmscan.c:3383
 reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349
 mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430
 tracehook_notify_resume include/linux/tracehook.h:197 [inline]
 exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
 swapgs_restore_regs_and_return_to_usermode+0x0/0x40

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30620 Comm: syz-executor.0 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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