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BUG: KCSAN: data-race in __add_to_page_cache_locked / nr_blockdev_pages

read-write to 0xffff88810be983d0 of 8 bytes by task 13808 on cpu 1:
 __add_to_page_cache_locked+0x39d/0x7b0 mm/filemap.c:888
 add_to_page_cache_lru+0xa0/0x1b0 mm/filemap.c:939
 page_cache_ra_unbounded+0x272/0x4c0 mm/readahead.c:222
 do_page_cache_ra mm/readahead.c:267 [inline]
 force_page_cache_ra+0x226/0x260 mm/readahead.c:298
 page_cache_sync_ra+0x194/0x1c0 mm/readahead.c:572
 page_cache_sync_readahead include/linux/pagemap.h:839 [inline]
 generic_file_buffered_read+0x388/0x23a0 mm/filemap.c:2235
 generic_file_read_iter+0x80/0x3d0 mm/filemap.c:2553
 blkdev_read_iter+0xb3/0xc0 fs/block_dev.c:1925
 call_read_iter include/linux/fs.h:1897 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x552/0x5c0 fs/read_write.c:496
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810be983d0 of 8 bytes by task 9172 on cpu 0:
 nr_blockdev_pages+0x7c/0xd0 fs/block_dev.c:946
 si_meminfo+0x3a/0x60 mm/page_alloc.c:5335
 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+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: 0 PID: 9172 Comm: kworker/0:5 Not tainted 5.10.0-rc5-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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