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BUG: KCSAN: data-race in __filemap_add_folio / nr_blockdev_pages

read-write to 0xffff8881004c1830 of 8 bytes by task 3286 on cpu 1:
 __filemap_add_folio+0x430/0x6f0 mm/filemap.c:928
 filemap_add_folio+0x9c/0x1b0 mm/filemap.c:980
 page_cache_ra_unbounded+0x1c1/0x350 mm/readahead.c:275
 do_page_cache_ra mm/readahead.c:327 [inline]
 force_page_cache_ra mm/readahead.c:356 [inline]
 page_cache_sync_ra+0x252/0x680 mm/readahead.c:575
 filemap_get_pages+0x2ca/0x11a0 mm/filemap.c:2590
 filemap_read+0x230/0x8c0 mm/filemap.c:2701
 blkdev_read_iter+0x228/0x2d0 block/fops.c:796
 new_sync_read fs/read_write.c:489 [inline]
 vfs_read+0x5cc/0x6f0 fs/read_write.c:570
 ksys_read+0xe8/0x1b0 fs/read_write.c:713
 __do_sys_read fs/read_write.c:722 [inline]
 __se_sys_read fs/read_write.c:720 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:720
 x64_sys_call+0x2a3b/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881004c1830 of 8 bytes by task 9 on cpu 0:
 nr_blockdev_pages+0x7c/0xd0 block/bdev.c:485
 si_meminfo+0x87/0xd0 mm/show_mem.c:80
 update_defense_level+0x49/0x5b0 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+0x4db/0xa20 kernel/workqueue.c:3319
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3400
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x0000000000000003 -> 0x0000000000000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.14.0-syzkaller-00685-g3ba7dfb8da62 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: events_long defense_work_handler
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