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BUG: KCSAN: data-race in __add_to_page_cache_locked / nr_blockdev_pages

write to 0xffff888101ee3c50 of 8 bytes by task 4561 on cpu 1:
 __add_to_page_cache_locked+0x39d/0x6b0 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
 ondemand_readahead+0x560/0x780 mm/readahead.c:267
 page_cache_async_ra+0x1aa/0x1d0 mm/readahead.c:607
 page_cache_async_readahead include/linux/pagemap.h:862 [inline]
 do_async_mmap_readahead+0x222/0x250 mm/filemap.c:2760
 filemap_fault+0x100/0xc10 mm/filemap.c:2815
 __do_fault mm/memory.c:3625 [inline]
 do_read_fault+0x3fb/0x720 mm/memory.c:4019
 do_fault mm/memory.c:4147 [inline]
 handle_pte_fault mm/memory.c:4387 [inline]
 __handle_mm_fault mm/memory.c:4522 [inline]
 handle_mm_fault+0x100c/0x1810 mm/memory.c:4620
 faultin_page mm/gup.c:851 [inline]
 __get_user_pages+0xa42/0x1000 mm/gup.c:1070
 populate_vma_page_range mm/gup.c:1403 [inline]
 __mm_populate+0x24d/0x380 mm/gup.c:1451
 mm_populate include/linux/mm.h:2591 [inline]
 vm_mmap_pgoff+0x14c/0x1d0 mm/util.c:524
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1634
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888101ee3c50 of 8 bytes by task 9747 on cpu 0:
 nr_blockdev_pages+0x7c/0xd0 fs/block_dev.c:942
 si_meminfo+0x3a/0x60 mm/page_alloc.c:5404
 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:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 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: 9747 Comm: kworker/0:5 Not tainted 5.11.0-rc6-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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