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BUG: KCSAN: data-race in lru_add_drain_all / pagevec_lru_move_fn

read to 0xffff88812be273a0 of 1 bytes by task 30517 on cpu 1:
 need_activate_page_drain mm/swap.c:304 [inline]
 lru_add_drain_all+0x319/0x350 mm/swap.c:733
 invalidate_bdev+0x6e/0x90 fs/block_dev.c:97
 __loop_clr_fd+0x250/0x720 drivers/block/loop.c:1128
 loop_clr_fd drivers/block/loop.c:1224 [inline]
 lo_ioctl+0x24c/0xc80 drivers/block/loop.c:1593
 __blkdev_driver_ioctl block/ioctl.c:304 [inline]
 blkdev_ioctl+0x979/0x1160 block/ioctl.c:606
 block_ioctl+0x95/0xc0 fs/block_dev.c:1954
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x991/0xc60 fs/ioctl.c:696
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:718
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88812be273a0 of 1 bytes by task 30513 on cpu 0:
 pagevec_reinit include/linux/pagevec.h:63 [inline]
 pagevec_lru_move_fn+0x163/0x180 mm/swap.c:216
 activate_page_drain mm/swap.c:299 [inline]
 lru_add_drain_cpu+0x23d/0x2e0 mm/swap.c:618
 lru_add_drain+0x35/0x80 mm/swap.c:689
 follow_page_pte+0xb3e/0xd20 mm/gup.c:287
 follow_pmd_mask mm/gup.c:415 [inline]
 follow_pud_mask mm/gup.c:460 [inline]
 follow_p4d_mask mm/gup.c:486 [inline]
 follow_page_mask+0x7b0/0x1100 mm/gup.c:545
 __get_user_pages+0x3a0/0x1160 mm/gup.c:843
 populate_vma_page_range+0xe6/0x100 mm/gup.c:1223
 __mm_populate+0x168/0x2a0 mm/gup.c:1271
 mm_populate include/linux/mm.h:2357 [inline]
 __do_sys_mlockall mm/mlock.c:823 [inline]
 __se_sys_mlockall mm/mlock.c:799 [inline]
 __x64_sys_mlockall+0x2e3/0x320 mm/mlock.c:799
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30513 Comm: syz-executor.5 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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