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BUG: KCSAN: data-race in wb_timer_fn / wbt_track

write to 0xffff888103a1ee04 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+0x570/0xa00 block/blk-wbt.c:374
 blk_stat_timer_fn+0x3f4/0x410 block/blk-stat.c:99
 call_timer_fn+0x2e/0x240 kernel/time/timer.c:1417
 expire_timers+0x116/0x260 kernel/time/timer.c:1462
 __run_timers+0x358/0x3f0 kernel/time/timer.c:1731
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1744
 __do_softirq+0x13c/0x2c3 kernel/softirq.c:343
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:650
 smpboot_thread_fn+0x34f/0x520 kernel/smpboot.c:165
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff888103a1ee04 of 4 bytes by task 14622 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+0x2d5/0x1040 block/blk-mq.c:2173
 __submit_bio_noacct_mq block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x78d/0x960 block/blk-core.c:1061
 submit_bio+0x200/0x360 block/blk-core.c:1131
 ext4_mpage_readpages+0x1565/0x15c0 fs/ext4/readpage.c:412
 ext4_readahead+0x99/0xa0 fs/ext4/inode.c:3261
 read_pages+0x9c/0x6e0 mm/readahead.c:130
 page_cache_ra_unbounded+0x46c/0x4c0 mm/readahead.c:238
 ondemand_readahead+0x560/0x780 mm/readahead.c:267
 page_cache_sync_ra+0x18f/0x1a0 mm/readahead.c:577
 page_cache_sync_readahead include/linux/pagemap.h:839 [inline]
 generic_file_buffered_read_get_pages+0x234/0xaf0 mm/filemap.c:2361
 generic_file_buffered_read+0x26e/0x9c0 mm/filemap.c:2481
 generic_file_read_iter+0x82/0x3e0 mm/filemap.c:2633
 ext4_file_read_iter+0x2e0/0x430 fs/ext4/file.c:74
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:788 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:867
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5e0/0xcf0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 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: 14622 Comm: syz-executor.2 Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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