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BUG: KCSAN: data-race in __delete_from_page_cache / nr_blockdev_pages

read-write to 0xffff88810be0ba10 of 8 bytes by task 15072 on cpu 1:
 page_cache_delete mm/filemap.c:154 [inline]
 __delete_from_page_cache+0x26c/0x340 mm/filemap.c:239
 __remove_mapping+0x3e4/0x480 mm/vmscan.c:930
 remove_mapping+0x22/0x60 mm/vmscan.c:952
 invalidate_complete_page mm/truncate.c:215 [inline]
 invalidate_inode_page+0x15d/0x190 mm/truncate.c:264
 __invalidate_mapping_pages+0x3e8/0x720 mm/truncate.c:592
 invalidate_mapping_pages+0x23/0x30 mm/truncate.c:635
 invalidate_bdev+0x61/0x70 fs/block_dev.c:97
 __loop_clr_fd+0x253/0x5a0 drivers/block/loop.c:1248
 loop_clr_fd drivers/block/loop.c:1345 [inline]
 lo_ioctl+0x9c2/0x1180 drivers/block/loop.c:1703
 __blkdev_driver_ioctl block/ioctl.c:228 [inline]
 blkdev_ioctl+0x1d6/0x3f0 block/ioctl.c:623
 block_ioctl+0x6d/0x80 fs/block_dev.c:1869
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810be0ba10 of 8 bytes by task 11995 on cpu 0:
 nr_blockdev_pages+0x7c/0xd0 fs/block_dev.c:946
 si_meminfo+0x3a/0x60 mm/page_alloc.c:5330
 update_defense_level+0x34/0x550 net/netfilter/ipvs/ip_vs_ctl.c:101
 defense_work_handler+0x1b/0x80 net/netfilter/ipvs/ip_vs_ctl.c:235
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/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: 11995 Comm: kworker/0:10 Not tainted 5.10.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_long defense_work_handler
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