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BUG: KCSAN: data-race in __add_to_page_cache_locked / nr_blockdev_pages

read to 0xffff888125664d68 of 8 bytes by task 30109 on cpu 1:
 nr_blockdev_pages+0x73/0xc0 fs/block_dev.c:952
 si_meminfo+0x3e/0x60 mm/page_alloc.c:5151
 update_defense_level+0x40/0xb50 net/netfilter/ipvs/ip_vs_ctl.c:101
 defense_work_handler+0x3d/0xd0 net/netfilter/ipvs/ip_vs_ctl.c:224
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

write to 0xffff888125664d68 of 8 bytes by task 12737 on cpu 0:
 __add_to_page_cache_locked+0x298/0x780 mm/filemap.c:890
 add_to_page_cache_lru+0xc4/0x260 mm/filemap.c:943
 pagecache_get_page+0x2ac/0x6f0 mm/filemap.c:1682
 find_or_create_page include/linux/pagemap.h:310 [inline]
 grow_dev_page fs/buffer.c:989 [inline]
 grow_buffers fs/buffer.c:1058 [inline]
 __getblk_slow fs/buffer.c:1085 [inline]
 __getblk_gfp+0x1fe/0x570 fs/buffer.c:1362
 __bread_gfp+0x38/0x1e0 fs/buffer.c:1396
 sb_bread include/linux/buffer_head.h:307 [inline]
 fat__get_entry+0x35e/0x4f0 fs/fat/dir.c:100
 fat_get_entry fs/fat/dir.c:128 [inline]
 fat_get_short_entry+0x103/0x200 fs/fat/dir.c:877
 fat_subdirs+0x6b/0x110 fs/fat/dir.c:943
 fat_read_root fs/fat/inode.c:1416 [inline]
 fat_fill_super+0x1552/0x1f50 fs/fat/inode.c:1862
 vfat_fill_super+0x3b/0x50 fs/fat/namei_vfat.c:1050
 mount_bdev+0x262/0x2d0 fs/super.c:1415
 vfat_mount+0x3e/0x60 fs/fat/namei_vfat.c:1057
 legacy_get_tree+0x7e/0xf0 fs/fs_context.c:647
 vfs_get_tree+0x56/0x1a0 fs/super.c:1545
 do_new_mount fs/namespace.c:2822 [inline]
 do_mount+0x1004/0x14f0 fs/namespace.c:3142
 ksys_mount+0xe8/0x160 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0x70/0x90 fs/namespace.c:3362
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12737 Comm: syz-executor.2 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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