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BUG: KCSAN: data-race in __add_to_page_cache_locked / nr_blockdev_pages

write to 0xffff88812b83acf0 of 8 bytes by task 28434 on cpu 1:
 __add_to_page_cache_locked+0x28a/0x800 mm/filemap.c:868
 add_to_page_cache_lru+0xc7/0x260 mm/filemap.c:921
 mpage_readpages+0x24e/0x400 fs/mpage.c:399
 blkdev_readpages+0x32/0x50 fs/block_dev.c:621
 read_pages+0xa2/0x360 mm/readahead.c:126
 __do_page_cache_readahead+0x358/0x380 mm/readahead.c:212
 force_page_cache_readahead+0x12c/0x1e0 mm/readahead.c:243
 page_cache_sync_readahead+0x1d1/0x1e0 mm/readahead.c:522
 generic_file_buffered_read mm/filemap.c:2036 [inline]
 generic_file_read_iter+0xf24/0x18c0 mm/filemap.c:2309
 blkdev_read_iter+0xae/0xe0 fs/block_dev.c:2053
 call_read_iter include/linux/fs.h:1901 [inline]
 new_sync_read+0x306/0x450 fs/read_write.c:415
 __vfs_read+0x9e/0xb0 fs/read_write.c:428
 vfs_read fs/read_write.c:462 [inline]
 vfs_read+0x13e/0x2b0 fs/read_write.c:447
 ksys_read+0xc5/0x1a0 fs/read_write.c:588
 __do_sys_read fs/read_write.c:598 [inline]
 __se_sys_read fs/read_write.c:596 [inline]
 __x64_sys_read+0x49/0x60 fs/read_write.c:596
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812b83acf0 of 8 bytes by task 48 on cpu 0:
 nr_blockdev_pages+0x6c/0xc0 fs/block_dev.c:953
 si_meminfo+0x3a/0x60 mm/page_alloc.c:5197
 update_defense_level+0x4a/0xa80 net/netfilter/ipvs/ip_vs_ctl.c:101
 defense_work_handler+0x3a/0xd0 net/netfilter/ipvs/ip_vs_ctl.c:224
 process_one_work+0x424/0x930 kernel/workqueue.c:2268
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2414
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 48 Comm: kworker/0:2 Not tainted 5.7.0-rc1-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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