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BUG: KCSAN: data-race in calc_wb_limits.part.0 / wbt_issue

write to 0xffff88821aa6fc04 of 4 bytes by interrupt on cpu 1:
 calc_wb_limits.part.0+0x70/0xa0 block/blk-wbt.c:304
 calc_wb_limits block/blk-wbt.c:298 [inline]
 scale_up block/blk-wbt.c:313 [inline]
 scale_up+0x7d/0x250 block/blk-wbt.c:309
 wb_timer_fn+0x2d6/0xad0 block/blk-wbt.c:382
 blk_stat_timer_fn+0x3af/0x3d0 block/blk-stat.c:99
 call_timer_fn+0x58/0x2e0 kernel/time/timer.c:1405
 expire_timers kernel/time/timer.c:1450 [inline]
 __run_timers kernel/time/timer.c:1774 [inline]
 __run_timers kernel/time/timer.c:1741 [inline]
 run_timer_softirq+0xb14/0xbd0 kernel/time/timer.c:1787
 __do_softirq+0x118/0x34a kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xb5/0xd0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:546 [inline]
 smp_apic_timer_interrupt+0xe2/0x270 arch/x86/kernel/apic/apic.c:1146
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
 kcsan_setup_watchpoint+0x25a/0x440 kernel/kcsan/core.c:530
 zap_pte_range mm/memory.c:1043 [inline]
 zap_pmd_range mm/memory.c:1184 [inline]
 zap_pud_range mm/memory.c:1213 [inline]
 zap_p4d_range mm/memory.c:1234 [inline]
 unmap_page_range+0xc3b/0x1a60 mm/memory.c:1255
 unmap_single_vma+0x13c/0x1f0 mm/memory.c:1300
 unmap_vmas+0xe2/0x1b0 mm/memory.c:1332
 exit_mmap+0x13e/0x2f0 mm/mmap.c:3130
 __mmput kernel/fork.c:1088 [inline]
 mmput+0xe2/0x260 kernel/fork.c:1109
 exec_mmap fs/exec.c:1051 [inline]
 flush_old_exec+0x5e7/0xf50 fs/exec.c:1284
 load_elf_binary+0x5e1/0x2c60 fs/binfmt_elf.c:848
 search_binary_handler fs/exec.c:1662 [inline]
 search_binary_handler+0x11c/0x3e0 fs/exec.c:1639
 exec_binprm fs/exec.c:1705 [inline]
 __do_execve_file.isra.0+0xb53/0x1120 fs/exec.c:1825
 do_execveat_common fs/exec.c:1871 [inline]
 do_execve fs/exec.c:1888 [inline]
 __do_sys_execve fs/exec.c:1964 [inline]
 __se_sys_execve fs/exec.c:1959 [inline]
 __x64_sys_execve+0x5e/0x70 fs/exec.c:1959
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88821aa6fc04 of 4 bytes by task 26617 on cpu 0:
 rwb_enabled block/blk-wbt.c:80 [inline]
 wbt_issue+0x33/0xf0 block/blk-wbt.c:607
 __rq_qos_issue+0x43/0x70 block/blk-rq-qos.c:54
 rq_qos_issue block/blk-rq-qos.h:159 [inline]
 blk_mq_start_request+0x310/0x360 block/blk-mq.c:662
 loop_queue_rq+0x5f/0x280 drivers/block/loop.c:1911
 blk_mq_dispatch_rq_list+0x9ca/0xe70 block/blk-mq.c:1246
 blk_mq_do_dispatch_sched+0x12b/0x270 block/blk-mq-sched.c:115
 blk_mq_sched_dispatch_requests+0x2b6/0x380 block/blk-mq-sched.c:211
 __blk_mq_run_hw_queue+0xb1/0x150 block/blk-mq.c:1382
 __blk_mq_delay_run_hw_queue+0x315/0x390 block/blk-mq.c:1459
 blk_mq_run_hw_queue+0xfa/0x1b0 block/blk-mq.c:1512
 blk_mq_sched_insert_requests+0x19c/0x270 block/blk-mq-sched.c:444
 blk_mq_flush_plug_list+0x2f0/0x4c0 block/blk-mq.c:1758
 blk_flush_plug_list+0x281/0x2b0 block/blk-core.c:1772
 blk_finish_plug block/blk-core.c:1789 [inline]
 blk_finish_plug+0x59/0x7a block/blk-core.c:1785
 read_pages+0xbc/0x2d0 mm/readahead.c:142
 __do_page_cache_readahead+0x358/0x380 mm/readahead.c:212
 force_page_cache_readahead+0x12c/0x1e0 mm/readahead.c:243
 page_cache_sync_readahead+0x1d1/0x1e0 mm/readahead.c:522
 generic_file_buffered_read mm/filemap.c:2029 [inline]
 generic_file_read_iter+0xeae/0x1490 mm/filemap.c:2302
 blkdev_read_iter+0xae/0xe0 fs/block_dev.c:2039
 call_read_iter include/linux/fs.h:1895 [inline]
 new_sync_read+0x306/0x450 fs/read_write.c:414
 __vfs_read+0x9e/0xb0 fs/read_write.c:427
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x13e/0x2b0 fs/read_write.c:446
 ksys_read+0xc5/0x1a0 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read fs/read_write.c:595 [inline]
 __x64_sys_read+0x49/0x60 fs/read_write.c:595
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26617 Comm: blkid Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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