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BUG: KCSAN: data-race in wb_timer_fn / wbt_wait

write to 0xffff8881295cb004 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+0x42d/0xa40 block/blk-wbt.c:382
 blk_stat_timer_fn+0x3f4/0x410 block/blk-stat.c:99
 call_timer_fn+0x30/0x2a0 kernel/time/timer.c:1413
 expire_timers+0x116/0x290 kernel/time/timer.c:1458
 __run_timers+0x348/0x3e0 kernel/time/timer.c:1755
 run_timer_softirq+0x2e/0x60 kernel/time/timer.c:1768
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x5d/0x80 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu+0x115/0x120 kernel/softirq.c:423
 sysvec_apic_timer_interrupt+0xba/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
 get_current arch/x86/include/asm/current.h:15 [inline]
 get_ctx kernel/kcsan/core.c:193 [inline]
 check_access kernel/kcsan/core.c:601 [inline]
 __tsan_read8+0x111/0x180 kernel/kcsan/core.c:801
 tomoyo_path_matches_pattern+0x29/0x120 security/tomoyo/util.c:919
 tomoyo_compare_name_union security/tomoyo/file.c:87 [inline]
 tomoyo_check_path_acl+0x9b/0xe0 security/tomoyo/file.c:260
 tomoyo_check_acl+0xcc/0x220 security/tomoyo/domain.c:175
 tomoyo_path_permission security/tomoyo/file.c:586 [inline]
 tomoyo_path_perm+0x22f/0x330 security/tomoyo/file.c:838
 tomoyo_inode_getattr+0x18/0x20 security/tomoyo/tomoyo.c:123
 security_inode_getattr+0x7f/0xd0 security/security.c:1278
 vfs_getattr fs/stat.c:121 [inline]
 vfs_statx+0x118/0x2b0 fs/stat.c:206
 vfs_lstat include/linux/fs.h:3178 [inline]
 __do_sys_newlstat fs/stat.c:374 [inline]
 __se_sys_newlstat+0x46/0x250 fs/stat.c:368
 __x64_sys_newlstat+0x2d/0x40 fs/stat.c:368
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881295cb004 of 4 bytes by task 16915 on cpu 1:
 rwb_enabled block/blk-wbt.c:80 [inline]
 bio_to_wbt_flags block/blk-wbt.c:543 [inline]
 wbt_wait+0x36/0x2b0 block/blk-wbt.c:576
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_submit_bio+0x244/0x1130 block/blk-mq.c:2168
 __submit_bio_noacct_mq block/blk-core.c:1179 [inline]
 submit_bio_noacct+0x772/0x950 block/blk-core.c:1212
 submit_bio+0x200/0x370 block/blk-core.c:1282
 submit_bh_wbc+0x397/0x3d0 fs/buffer.c:3070
 submit_bh fs/buffer.c:3076 [inline]
 __sync_dirty_buffer+0x12c/0x1d0 fs/buffer.c:3171
 sync_dirty_buffer+0x16/0x20 fs/buffer.c:3184
 __ext4_handle_dirty_metadata+0x1d1/0x5a0 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:2043
 ext4_add_entry+0x655/0x21a0 fs/ext4/namei.c:2253
 ext4_add_nondir+0x50/0x1a0 fs/ext4/namei.c:2587
 ext4_symlink+0x5be/0x7e0 fs/ext4/namei.c:3384
 vfs_symlink+0x218/0x2d0 fs/namei.c:3959
 do_symlinkat+0xee/0x280 fs/namei.c:3986
 __do_sys_symlink fs/namei.c:4005 [inline]
 __se_sys_symlink fs/namei.c:4003 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4003
 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: 16915 Comm: syz-executor.1 Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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