syzbot

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BUG: KCSAN: data-race in balance_pgdat / shrink_node

read to 0xffff88812bcfb478 of 8 bytes by task 4000 on cpu 1:
 shrink_node+0x9c5/0xfe0 mm/vmscan.c:2733
 shrink_zones mm/vmscan.c:2996 [inline]
 do_try_to_free_pages+0x245/0xb60 mm/vmscan.c:3049
 try_to_free_pages+0x1f5/0x4a0 mm/vmscan.c:3288
 __perform_reclaim mm/page_alloc.c:4124 [inline]
 __alloc_pages_direct_reclaim mm/page_alloc.c:4145 [inline]
 __alloc_pages_slowpath+0x45c/0xee0 mm/page_alloc.c:4562
 __alloc_pages_nodemask+0x2c8/0x310 mm/page_alloc.c:4776
 alloc_pages_current+0xd1/0x170 mm/mempolicy.c:2207
 alloc_pages include/linux/gfp.h:532 [inline]
 __page_cache_alloc mm/filemap.c:981 [inline]
 __page_cache_alloc+0x183/0x1a0 mm/filemap.c:966
 pagecache_get_page+0x24b/0x6f0 mm/filemap.c:1671
 filemap_fault+0xc95/0x10a0 mm/filemap.c:2510
 ext4_filemap_fault+0x59/0x72 fs/ext4/inode.c:5977
 __do_fault+0xae/0x1f0 mm/memory.c:3188
 do_read_fault mm/memory.c:3585 [inline]
 do_fault mm/memory.c:3714 [inline]
 handle_pte_fault mm/memory.c:3945 [inline]
 __handle_mm_fault+0x270d/0x2e00 mm/memory.c:4075
 handle_mm_fault+0x21b/0x530 mm/memory.c:4112
 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
 __do_page_fault+0x456/0x8d0 arch/x86/mm/fault.c:1506
 do_page_fault+0x38/0x194 arch/x86/mm/fault.c:1530
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1203

write to 0xffff88812bcfb478 of 8 bytes by task 1769 on cpu 0:
 snapshot_refaults mm/vmscan.c:3013 [inline]
 balance_pgdat+0xc81/0xda0 mm/vmscan.c:3761
 kswapd+0x35b/0x800 mm/vmscan.c:3948
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1769 Comm: kswapd0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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