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BUG: KCSAN: data-race in lru_add_drain_all / pagevec_lru_move_fn

write to 0xffff88813bd27b70 of 1 bytes by task 21504 on cpu 1:
 pagevec_reinit include/linux/pagevec.h:60 [inline]
 pagevec_lru_move_fn+0x2a2/0x2d0 mm/swap.c:226
 activate_page_drain mm/swap.c:332 [inline]
 lru_add_drain_cpu+0x21c/0x250 mm/swap.c:641
 lru_add_drain mm/swap.c:720 [inline]
 __pagevec_release+0x5a/0xd0 mm/swap.c:951
 pagevec_release include/linux/pagevec.h:85 [inline]
 invalidate_inode_pages2_range+0x69f/0x780 mm/truncate.c:780
 __iomap_dio_rw+0x52e/0x9b0 fs/iomap/direct-io.c:499
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:605
 ext4_dio_write_iter fs/ext4/file.c:552 [inline]
 ext4_file_write_iter+0xe06/0x1090 fs/ext4/file.c:662
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4b0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x42a/0x780 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88813bd27b70 of 1 bytes by task 1660 on cpu 0:
 pagevec_count include/linux/pagevec.h:65 [inline]
 need_activate_page_drain mm/swap.c:337 [inline]
 lru_add_drain_all+0x216/0x3c0 mm/swap.c:828
 khugepaged_do_scan+0x47/0x320 mm/khugepaged.c:2202
 khugepaged+0x75/0x650 mm/khugepaged.c:2263
 kthread+0x1fd/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1660 Comm: khugepaged Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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