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BUG: KCSAN: data-race in __filemap_add_folio / nr_blockdev_pages

read-write to 0xffff8881005f2af8 of 8 bytes by task 23727 on cpu 1:
 __filemap_add_folio+0x5b9/0x7d0 mm/filemap.c:919
 filemap_add_folio+0x1d9/0x360 mm/filemap.c:966
 __filemap_get_folio_mpol+0x326/0x650 mm/filemap.c:2016
 __filemap_get_folio include/linux/pagemap.h:763 [inline]
 grow_dev_folio fs/buffer.c:1050 [inline]
 grow_buffers fs/buffer.c:1116 [inline]
 __getblk_slow fs/buffer.c:1134 [inline]
 bdev_getblk+0x174/0x3f0 fs/buffer.c:1461
 getblk_unmovable include/linux/buffer_head.h:369 [inline]
 ext4_getblk+0x1b6/0x510 fs/ext4/inode.c:999
 ext4_bread+0x28/0x110 fs/ext4/inode.c:1047
 ext4_quota_read+0xe8/0x260 fs/ext4/super.c:7304
 read_blk fs/quota/quota_tree.c:61 [inline]
 find_tree_dqentry+0x11c/0x8c0 fs/quota/quota_tree.c:671
 find_dqentry fs/quota/quota_tree.c:716 [inline]
 qtree_read_dquot+0x35c/0x4a0 fs/quota/quota_tree.c:736
 v2_read_dquot+0x98/0xd0 fs/quota/quota_v2.c:344
 dquot_acquire+0xce/0x2b0 fs/quota/dquot.c:464
 ext4_acquire_dquot+0x15f/0x200 fs/ext4/super.c:6982
 dqget+0x527/0x8c0 fs/quota/dquot.c:980
 __dquot_initialize+0x20c/0x7c0 fs/quota/dquot.c:1508
 dquot_initialize fs/quota/dquot.c:1570 [inline]
 dquot_file_open+0x6f/0x80 fs/quota/dquot.c:2221
 ext4_file_open+0x2c5/0x600 fs/ext4/file.c:927
 do_dentry_open+0x54b/0xa60 fs/open.c:962
 vfs_open+0x37/0x1e0 fs/open.c:1094
 do_open fs/namei.c:4628 [inline]
 path_openat+0x1ddd/0x23b0 fs/namei.c:4787
 do_filp_open+0x109/0x230 fs/namei.c:4814
 do_sys_openat2+0xa6/0x150 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1447
 x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 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 0xffff8881005f2af8 of 8 bytes by task 20921 on cpu 0:
 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: 0x0000000000000007 -> 0x0000000000000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20921 Comm: kworker/0:12 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_long defense_work_handler
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