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BUG: KCSAN: data-race in wb_timer_fn / wbt_track

write to 0xffff888102a13404 of 4 bytes by interrupt on cpu 0:
 calc_wb_limits block/blk-wbt.c:304 [inline]
 scale_up block/blk-wbt.c:313 [inline]
 wb_timer_fn+0x403/0xa00 block/blk-wbt.c:382
 blk_stat_timer_fn+0x3f4/0x410 block/blk-stat.c:99
 call_timer_fn+0x2e/0x240 kernel/time/timer.c:1410
 expire_timers+0x116/0x260 kernel/time/timer.c:1455
 __run_timers+0x328/0x3c0 kernel/time/timer.c:1747
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1760
 __do_softirq+0x12c/0x2b1 kernel/softirq.c:298
 asm_call_irq_on_stack+0xf/0x20
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
 do_softirq_own_stack+0x32/0x40 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu+0xb2/0xc0 kernel/softirq.c:423
 sysvec_apic_timer_interrupt+0x74/0x90 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:631
 native_restore_fl arch/x86/include/asm/irqflags.h:41 [inline]
 arch_local_irq_restore arch/x86/include/asm/irqflags.h:84 [inline]
 kcsan_setup_watchpoint+0x1ec/0x4d0 kernel/kcsan/core.c:591
 tomoyo_get_absolute_path security/tomoyo/realpath.c:107 [inline]
 tomoyo_realpath_from_path+0x2cd/0x3b0 security/tomoyo/realpath.c:276
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0xaf/0x370 security/tomoyo/file.c:771
 tomoyo_file_open+0xd3/0xf0 security/tomoyo/tomoyo.c:313
 security_file_open+0x3f/0x90 security/security.c:1575
 do_dentry_open+0x22d/0x870 fs/open.c:804
 vfs_open+0x43/0x50 fs/open.c:931
 do_open fs/namei.c:3252 [inline]
 path_openat+0x1844/0x20a0 fs/namei.c:3369
 do_filp_open+0xbd/0x1d0 fs/namei.c:3396
 do_sys_openat2+0xa3/0x240 fs/open.c:1168
 do_sys_open fs/open.c:1184 [inline]
 __do_sys_open fs/open.c:1192 [inline]
 __se_sys_open fs/open.c:1188 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1188
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888102a13404 of 4 bytes by task 29631 on cpu 1:
 rwb_enabled block/blk-wbt.c:80 [inline]
 bio_to_wbt_flags block/blk-wbt.c:543 [inline]
 wbt_track+0x23/0x130 block/blk-wbt.c:592
 __rq_qos_track+0x50/0x90 block/blk-rq-qos.c:81
 rq_qos_track block/blk-rq-qos.h:189 [inline]
 blk_mq_submit_bio+0x2c0/0x1020 block/blk-mq.c:2187
 __submit_bio_noacct_mq block/blk-core.c:1026 [inline]
 submit_bio_noacct+0x77d/0x930 block/blk-core.c:1059
 submit_bio+0x1f3/0x360 block/blk-core.c:1129
 submit_bh_wbc+0x38c/0x3d0 fs/buffer.c:3054
 submit_bh fs/buffer.c:3060 [inline]
 __sync_dirty_buffer+0x12c/0x1d0 fs/buffer.c:3155
 sync_dirty_buffer+0x16/0x20 fs/buffer.c:3168
 __ext4_handle_dirty_metadata+0x1d1/0x590 fs/ext4/ext4_jbd2.c:364
 ext4_handle_dirty_dirblock+0x184/0x330 fs/ext4/namei.c:411
 add_dirent_to_buf+0x475/0x5e0 fs/ext4/namei.c:2042
 ext4_add_entry+0x60e/0x2160 fs/ext4/namei.c:2248
 ext4_add_nondir+0x50/0x190 fs/ext4/namei.c:2582
 ext4_symlink+0x532/0x770 fs/ext4/namei.c:3406
 vfs_symlink+0x216/0x2d0 fs/namei.c:3960
 do_symlinkat+0xee/0x280 fs/namei.c:3987
 __do_sys_symlink fs/namei.c:4006 [inline]
 __se_sys_symlink fs/namei.c:4004 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4004
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29631 Comm: syz-executor.2 Not tainted 5.10.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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