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BUG: KCSAN: data-race in lru_add_drain_all / lru_cache_add

write to 0xffff88813bc27550 of 1 bytes by task 11443 on cpu 0:
 pagevec_add include/linux/pagevec.h:74 [inline]
 lru_cache_add+0x7c/0x160 mm/swap.c:461
 shmem_getpage_gfp+0x8c4/0x1980 mm/shmem.c:1934
 shmem_fault+0x16c/0x450 mm/shmem.c:2116
 __do_fault mm/memory.c:3637 [inline]
 do_read_fault+0x2e1/0x530 mm/memory.c:3939
 do_fault mm/memory.c:4067 [inline]
 handle_pte_fault mm/memory.c:4318 [inline]
 __handle_mm_fault mm/memory.c:4453 [inline]
 handle_mm_fault+0x1019/0x1840 mm/memory.c:4551
 faultin_page mm/gup.c:850 [inline]
 __get_user_pages+0xa47/0x1000 mm/gup.c:1069
 populate_vma_page_range mm/gup.c:1402 [inline]
 __mm_populate+0x24d/0x380 mm/gup.c:1450
 mm_populate include/linux/mm.h:2570 [inline]
 vm_mmap_pgoff+0x14c/0x1d0 mm/util.c:524
 ksys_mmap_pgoff+0xe1/0x380 mm/mmap.c:1632
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813bc27550 of 1 bytes by task 1639 on cpu 1:
 pagevec_count include/linux/pagevec.h:61 [inline]
 lru_add_drain_all+0x108/0x3c0 mm/swap.c:813
 khugepaged_do_scan+0x47/0x330 mm/khugepaged.c:2213
 khugepaged+0x75/0x680 mm/khugepaged.c:2274
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1639 Comm: khugepaged Tainted: G        W         5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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