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BUG: KCSAN: data-race in __filemap_add_folio / nr_blockdev_pages

read-write to 0xffff8881004811f8 of 8 bytes by task 7592 on cpu 0:
 __filemap_add_folio+0x5b9/0x7d0 mm/filemap.c:919
 filemap_add_folio+0x1d9/0x360 mm/filemap.c:966
 page_cache_ra_unbounded+0x205/0x450 mm/readahead.c:280
 do_page_cache_ra mm/readahead.c:332 [inline]
 page_cache_ra_order+0x145/0x220 mm/readahead.c:535
 page_cache_async_ra+0x383/0x4c0 mm/readahead.c:697
 filemap_readahead mm/filemap.c:2658 [inline]
 filemap_get_pages+0x51e/0x11c0 mm/filemap.c:2704
 filemap_read+0x231/0xa00 mm/filemap.c:2800
 blkdev_read_iter+0x22d/0x2e0 block/fops.c:856
 do_iter_readv_writev+0x4a1/0x540 fs/read_write.c:-1
 vfs_readv+0x1ea/0x690 fs/read_write.c:1018
 do_preadv fs/read_write.c:1132 [inline]
 __do_sys_preadv2 fs/read_write.c:1191 [inline]
 __se_sys_preadv2+0xfc/0x1c0 fs/read_write.c:1182
 __x64_sys_preadv2+0x67/0x80 fs/read_write.c:1182
 x64_sys_call+0xc61/0x3000 arch/x86/include/generated/asm/syscalls_64.h:328
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881004811f8 of 8 bytes by task 2970 on cpu 1:
 nr_blockdev_pages+0x7e/0xd0 block/bdev.c:540
 si_meminfo+0x87/0xd0 mm/show_mem.c:80
 update_defense_level+0x47/0x5c0 net/netfilter/ipvs/ip_vs_ctl.c:101
 defense_work_handler+0x1f/0x80 net/netfilter/ipvs/ip_vs_ctl.c:234
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x00000000000001f8 -> 0x00000000000001fb

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2970 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_long defense_work_handler
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