syzbot

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BUG: KCSAN: data-race in __filemap_add_folio / nr_blockdev_pages

read-write to 0xffff888100480bb8 of 8 bytes by task 3841 on cpu 1:
 __filemap_add_folio+0x5b9/0x7d0 mm/filemap.c:931
 filemap_add_folio+0x1d9/0x360 mm/filemap.c:978
 __filemap_get_folio+0x31e/0x650 mm/filemap.c:2022
 grow_dev_folio fs/buffer.c:1050 [inline]
 grow_buffers fs/buffer.c:1116 [inline]
 __getblk_slow fs/buffer.c:1134 [inline]
 bdev_getblk+0x14d/0x3b0 fs/buffer.c:1461
 ext4_sb_breadahead_unmovable+0x45/0x180 fs/ext4/super.c:279
 __ext4_get_inode_loc+0x709/0x930 fs/ext4/inode.c:4920
 __ext4_get_inode_loc_noinmem fs/ext4/inode.c:4950 [inline]
 __ext4_iget+0x2ea/0x22d0 fs/ext4/inode.c:5225
 __ext4_fill_super fs/ext4/super.c:5512 [inline]
 ext4_fill_super+0x2992/0x3810 fs/ext4/super.c:5736
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1691
 get_tree_bdev+0x1f/0x30 fs/super.c:1714
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5768
 vfs_get_tree+0x57/0x1d0 fs/super.c:1751
 fc_mount fs/namespace.c:1208 [inline]
 do_new_mount_fc fs/namespace.c:3651 [inline]
 do_new_mount+0x24d/0x660 fs/namespace.c:3727
 path_mount+0x4a5/0xb70 fs/namespace.c:4037
 do_mount fs/namespace.c:4050 [inline]
 __do_sys_mount fs/namespace.c:4238 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4215
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4215
 x64_sys_call+0x2b51/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100480bb8 of 8 bytes by task 3420 on cpu 0:
 nr_blockdev_pages+0x7e/0xd0 block/bdev.c:523
 si_meminfo+0x87/0xd0 mm/show_mem.c:80
 update_defense_level+0x47/0x5c0 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:3263 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000000003 -> 0x0000000000000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3420 Comm: kworker/0:4 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_long defense_work_handler
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