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BUG: KCSAN: data-race in __filemap_add_folio / nr_blockdev_pages

read-write to 0xffff8881005f0578 of 8 bytes by task 4309 on cpu 0:
 __filemap_add_folio+0x671/0x8a0 mm/filemap.c:919
 filemap_add_folio+0x1d3/0x350 mm/filemap.c:966
 page_cache_ra_unbounded+0x204/0x440 mm/readahead.c:280
 do_page_cache_ra mm/readahead.c:332 [inline]
 force_page_cache_ra mm/readahead.c:361 [inline]
 page_cache_sync_ra+0x26e/0x6a0 mm/readahead.c:579
 filemap_get_pages+0x30a/0x1260 mm/filemap.c:2690
 filemap_read+0x231/0xa10 mm/filemap.c:2800
 blkdev_read_iter+0x22d/0x2e0 block/fops.c:856
 new_sync_read fs/read_write.c:493 [inline]
 vfs_read+0x6c0/0x7f0 fs/read_write.c:574
 ksys_read+0xdc/0x1a0 fs/read_write.c:717
 __do_sys_read fs/read_write.c:726 [inline]
 __se_sys_read fs/read_write.c:724 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:724
 x64_sys_call+0x2886/0x3020 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881005f0578 of 8 bytes by task 4244 on cpu 1:
 nr_blockdev_pages+0x7e/0xd0 block/bdev.c:539
 si_meminfo+0x87/0xd0 mm/show_mem.c:80
 update_defense_level+0x47/0x5d0 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:3275 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3358
 worker_thread+0x581/0x770 kernel/workqueue.c:3439
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000000007 -> 0x0000000000000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4244 Comm: kworker/1:28 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Workqueue: events_long defense_work_handler
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