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BUG: KCSAN: data-race in wbt_inflight_cb / wbt_wait

write to 0xffff888128a15e40 of 8 bytes by task 27290 on cpu 0:
 wb_timestamp block/blk-wbt.c:89 [inline]
 wbt_wait+0x12b/0x2b0 block/blk-wbt.c:579
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_make_request+0x234/0x1070 block/blk-mq.c:2050
 do_make_request block/blk-core.c:1084 [inline]
 generic_make_request+0x240/0x5d0 block/blk-core.c:1156
 submit_bio+0x200/0x370 block/blk-core.c:1275
 iomap_dio_submit_bio fs/iomap/direct-io.c:75 [inline]
 iomap_dio_bio_actor+0x89d/0xad0 fs/iomap/direct-io.c:310
 iomap_dio_actor+0x1ec/0x340 fs/iomap/direct-io.c:385
 iomap_apply+0x1da/0x520 fs/iomap/apply.c:80
 iomap_dio_rw+0x501/0x8c0 fs/iomap/direct-io.c:501
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x3bc/0x420 fs/ext4/file.c:129
 call_read_iter include/linux/fs.h:1902 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:312
 do_splice_to fs/splice.c:870 [inline]
 splice_direct_to_actor+0x2a8/0x660 fs/splice.c:950
 do_splice_direct+0xf2/0x170 fs/splice.c:1059
 do_sendfile+0x562/0xb10 fs/read_write.c:1540
 __do_sys_sendfile64 fs/read_write.c:1601 [inline]
 __se_sys_sendfile64 fs/read_write.c:1587 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1587
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888128a15e40 of 8 bytes by task 27262 on cpu 1:
 close_io block/blk-wbt.c:444 [inline]
 get_limit block/blk-wbt.c:474 [inline]
 wbt_inflight_cb+0x19a/0x220 block/blk-wbt.c:495
 rq_qos_wait+0xac/0x220 block/blk-rq-qos.c:266
 __wbt_wait block/blk-wbt.c:518 [inline]
 wbt_wait+0x1bb/0x2b0 block/blk-wbt.c:583
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_make_request+0x234/0x1070 block/blk-mq.c:2050
 do_make_request block/blk-core.c:1084 [inline]
 generic_make_request+0x240/0x5d0 block/blk-core.c:1156
 submit_bio+0x200/0x370 block/blk-core.c:1275
 ext4_io_submit+0xcd/0xf0 fs/ext4/page-io.c:382
 ext4_writepages+0x143a/0x1ef0 fs/ext4/inode.c:2802
 do_writepages+0x7b/0x150 mm/page-writeback.c:2354
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:421
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:456
 ext4_alloc_da_blocks+0x4c/0x130 fs/ext4/inode.c:3146
 ext4_release_file+0x5b/0x1c0 fs/ext4/file.c:142
 __fput+0x1df/0x460 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:239 [inline]
 __prepare_exit_to_usermode+0x1c6/0x230 arch/x86/entry/common.c:269
 __syscall_return_slowpath+0x47/0x60 arch/x86/entry/common.c:352
 do_syscall_64+0x5d/0xb0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27262 Comm: syz-executor.5 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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