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BUG: KCSAN: data-race in __delete_from_page_cache / nr_blockdev_pages

write to 0xffff8881206ebab0 of 8 bytes by task 12893 on cpu 1:
 page_cache_delete mm/filemap.c:153 [inline]
 __delete_from_page_cache+0x293/0x390 mm/filemap.c:238
 __remove_mapping+0x384/0x430 mm/vmscan.c:932
 remove_mapping+0x22/0x60 mm/vmscan.c:954
 invalidate_complete_page mm/truncate.c:215 [inline]
 invalidate_inode_page+0x15d/0x190 mm/truncate.c:264
 invalidate_mapping_pages+0x3eb/0x6f0 mm/truncate.c:607
 invalidate_bdev+0x61/0x70 fs/block_dev.c:97
 __loop_clr_fd+0x258/0x5b0 drivers/block/loop.c:1243
 loop_clr_fd drivers/block/loop.c:1340 [inline]
 lo_ioctl+0x9d1/0x1190 drivers/block/loop.c:1698
 __blkdev_driver_ioctl block/ioctl.c:224 [inline]
 blkdev_ioctl+0x1b2/0x3f0 block/ioctl.c:620
 block_ioctl+0x6d/0x80 fs/block_dev.c:1988
 vfs_ioctl fs/ioctl.c:48 [inline]
 ksys_ioctl fs/ioctl.c:753 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0xc9/0x130 fs/ioctl.c:760
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881206ebab0 of 8 bytes by task 12 on cpu 0:
 nr_blockdev_pages+0x6c/0xb0 fs/block_dev.c:933
 si_meminfo+0x3a/0x60 mm/page_alloc.c:5238
 update_defense_level+0x34/0x550 net/netfilter/ipvs/ip_vs_ctl.c:101
 defense_work_handler+0x1a/0x80 net/netfilter/ipvs/ip_vs_ctl.c:224
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events defense_work_handler
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