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BUG: KCSAN: data-race in __pagevec_lru_add / lru_add_drain_all

write to 0xffff88813bc27970 of 1 bytes by task 8131 on cpu 0:
 pagevec_reinit include/linux/pagevec.h:60 [inline]
 __pagevec_lru_add+0x24b/0x280 mm/swap.c:1031
 lru_add_drain_cpu+0x6a/0x250 mm/swap.c:616
 lru_add_drain mm/swap.c:720 [inline]
 __pagevec_release+0x5a/0xd0 mm/swap.c:951
 pagevec_release include/linux/pagevec.h:85 [inline]
 mpage_prepare_extent_to_map+0x5ce/0x630 fs/ext4/inode.c:2639
 ext4_writepages+0x674/0x1e50 fs/ext4/inode.c:2755
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 ext4_sync_file+0x105/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2737 [inline]
 ext4_buffered_write_iter+0x384/0x3d0 fs/ext4/file.c:278
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6d4/0x7c0 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88813bc27970 of 1 bytes by task 1661 on cpu 1:
 pagevec_count include/linux/pagevec.h:65 [inline]
 lru_add_drain_all+0x108/0x3c0 mm/swap.c:823
 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: 1 PID: 1661 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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