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BUG: KCSAN: data-race in rq_depth_calc_max_depth / wbt_inflight_cb

write to 0xffff8881291009e0 of 4 bytes by interrupt on cpu 0:
 rq_depth_calc_max_depth+0xa5/0x160 block/blk-rq-qos.c:157
 rq_depth_scale_up+0x71/0xa0 block/blk-rq-qos.c:174
 scale_up+0x40/0x250 block/blk-wbt.c:311
 wb_timer_fn+0x2cd/0xad0 block/blk-wbt.c:393
 blk_stat_timer_fn+0x3b0/0x3d0 block/blk-stat.c:99
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xc0c/0xcd0 kernel/time/timer.c:1786
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 preempt_count arch/x86/include/asm/preempt.h:26 [inline]
 check_kcov_mode kernel/kcov.c:153 [inline]
 __sanitizer_cov_trace_pc+0x14/0x50 kernel/kcov.c:187
 PageReferenced include/linux/page-flags.h:315 [inline]
 mark_page_accessed+0xb2/0x520 mm/swap.c:377
 touch_buffer fs/buffer.c:63 [inline]
 __find_get_block+0x246/0x760 fs/buffer.c:1340
 sb_find_get_block include/linux/buffer_head.h:338 [inline]
 recently_deleted fs/ext4/ialloc.c:677 [inline]
 find_inode_bit.isra.0+0x161/0x300 fs/ext4/ialloc.c:717
 __ext4_new_inode+0xd45/0x2f10 fs/ext4/ialloc.c:909
 ext4_symlink+0x31c/0x9b0 fs/ext4/namei.c:3275
 vfs_symlink fs/namei.c:4131 [inline]
 vfs_symlink+0x218/0x310 fs/namei.c:4117
 do_symlinkat+0x1a5/0x1e0 fs/namei.c:4158
 __do_sys_symlink fs/namei.c:4177 [inline]
 __se_sys_symlink fs/namei.c:4175 [inline]
 __x64_sys_symlink+0x3f/0x50 fs/namei.c:4175
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881291009e0 of 4 bytes by task 14964 on cpu 1:
 get_limit block/blk-wbt.c:481 [inline]
 wbt_inflight_cb+0xc0/0x230 block/blk-wbt.c:503
 rq_qos_wait+0x283/0x320 block/blk-rq-qos.c:266
 __wbt_wait block/blk-wbt.c:526 [inline]
 wbt_wait+0x161/0x250 block/blk-wbt.c:591
 __rq_qos_throttle+0x47/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_make_request+0x29c/0xf60 block/blk-mq.c:1932
 generic_make_request block/blk-core.c:1066 [inline]
 generic_make_request+0x196/0x700 block/blk-core.c:1008
 submit_bio+0x96/0x3c0 block/blk-core.c:1192
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3135
 submit_bh fs/buffer.c:3141 [inline]
 __sync_dirty_buffer+0xd3/0x210 fs/buffer.c:3227
 sync_dirty_buffer+0x24/0x40 fs/buffer.c:3240
 __ext4_handle_dirty_metadata+0x19c/0x3e0 fs/ext4/ext4_jbd2.c:316
 ext4_handle_dirty_dirblock+0x20a/0x280 fs/ext4/namei.c:404
 ext4_delete_entry+0x266/0x2c0 fs/ext4/namei.c:2509
 ext4_rmdir fs/ext4/namei.c:3115 [inline]
 ext4_rmdir+0x3ca/0x700 fs/ext4/namei.c:3067
 vfs_rmdir fs/namei.c:3882 [inline]
 vfs_rmdir+0x119/0x300 fs/namei.c:3861
 do_rmdir+0x2cb/0x300 fs/namei.c:3944
 __do_sys_rmdir fs/namei.c:3962 [inline]
 __se_sys_rmdir fs/namei.c:3960 [inline]
 __x64_sys_rmdir+0x2f/0x40 fs/namei.c:3960
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14964 Comm: syz-executor.0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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