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BUG: KCSAN: data-race in lru_add_drain_all / mark_page_lazyfree

read to 0xffff88812bf27420 of 1 bytes by task 9707 on cpu 0:
 lru_add_drain_all+0x1b9/0x350 mm/swap.c:732
 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 0xffff88812bf27420 of 1 bytes by task 9700 on cpu 1:
 pagevec_add include/linux/pagevec.h:81 [inline]
 mark_page_lazyfree+0x32a/0x4a0 mm/swap.c:681
 madvise_free_pte_range+0xd66/0x12d0 mm/madvise.c:673
 walk_pmd_range mm/pagewalk.c:53 [inline]
 walk_pud_range mm/pagewalk.c:112 [inline]
 walk_p4d_range mm/pagewalk.c:139 [inline]
 walk_pgd_range mm/pagewalk.c:166 [inline]
 __walk_page_range+0x9d8/0xed0 mm/pagewalk.c:261
 walk_page_range+0x133/0x260 mm/pagewalk.c:349
 madvise_free_single_vma+0x2ea/0x410 mm/madvise.c:719
 madvise_dontneed_free mm/madvise.c:805 [inline]
 madvise_vma mm/madvise.c:942 [inline]
 __do_sys_madvise+0x44c/0x1150 mm/madvise.c:1121
 __se_sys_madvise mm/madvise.c:1047 [inline]
 __x64_sys_madvise+0x4c/0x60 mm/madvise.c:1047
 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: 1 PID: 9700 Comm: syz-executor.3 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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