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BUG: KCSAN: data-race in __filemap_add_folio / nr_blockdev_pages

read-write to 0xffff8881004c11f0 of 8 bytes by task 18991 on cpu 0:
 __filemap_add_folio+0x5b5/0x7f0 mm/filemap.c:928
 filemap_add_folio+0x9f/0x1b0 mm/filemap.c:969
 __filemap_get_folio+0x340/0x6b0 mm/filemap.c:1979
 grow_dev_folio fs/buffer.c:1039 [inline]
 grow_buffers fs/buffer.c:1105 [inline]
 __getblk_slow fs/buffer.c:1131 [inline]
 bdev_getblk+0x173/0x3b0 fs/buffer.c:1431
 getblk_unmovable include/linux/buffer_head.h:368 [inline]
 ext4_getblk+0x1bf/0x550 fs/ext4/inode.c:868
 ext4_bread_batch+0x5b/0x360 fs/ext4/inode.c:937
 __ext4_find_entry+0x85b/0xf40 fs/ext4/namei.c:1603
 ext4_lookup_entry fs/ext4/namei.c:1705 [inline]
 ext4_lookup+0xbd/0x3a0 fs/ext4/namei.c:1773
 lookup_open fs/namei.c:3644 [inline]
 open_last_lookups fs/namei.c:3765 [inline]
 path_openat+0xd76/0x2000 fs/namei.c:4001
 do_filp_open+0x115/0x240 fs/namei.c:4031
 do_sys_openat2+0xaa/0x110 fs/open.c:1429
 do_sys_open fs/open.c:1444 [inline]
 __do_sys_openat fs/open.c:1460 [inline]
 __se_sys_openat fs/open.c:1455 [inline]
 __x64_sys_openat+0xf8/0x120 fs/open.c:1455
 x64_sys_call+0x1ac/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881004c11f0 of 8 bytes by task 3378 on cpu 1:
 nr_blockdev_pages+0x7c/0xd0 block/bdev.c:485
 si_meminfo+0x87/0xd0 mm/show_mem.c:80
 update_defense_level+0x4b/0x5c0 net/netfilter/ipvs/ip_vs_ctl.c:102
 defense_work_handler+0x1f/0x80 net/netfilter/ipvs/ip_vs_ctl.c:235
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4de/0xa20 kernel/workqueue.c:3319
 worker_thread+0x52c/0x710 kernel/workqueue.c:3400
 kthread+0x4b7/0x540 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000000003 -> 0x0000000000000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3378 Comm: kworker/1:4 Not tainted 6.15.0-rc1-syzkaller-00333-g5aaaedb0cb54 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: events_long defense_work_handler
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