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BUG: KCSAN: data-race in bio_endio / blk_throtl_bio

read to 0xffff8880a64b9514 of 2 bytes by interrupt on cpu 1:
 bio_remaining_done block/bio.c:1757 [inline]
 bio_endio+0x3e/0x4f0 block/bio.c:1787
 req_bio_endio block/blk-core.c:242 [inline]
 blk_update_request+0x427/0x7b0 block/blk-core.c:1462
 scsi_end_request+0x6b/0x3e0 drivers/scsi/scsi_lib.c:579
 scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:963
 scsi_finish_command+0x280/0x380 drivers/scsi/scsi.c:228
 scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1477
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __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]
 do_IRQ+0x81/0x130 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x19
 __sanitizer_cov_trace_const_cmp4+0x1/0x20 kernel/kcov.c:188
 hrtimer_start_expires include/linux/hrtimer.h:435 [inline]
 hrtimer_sleeper_start_expires kernel/time/hrtimer.c:1792 [inline]
 do_nanosleep+0xfa/0x320 kernel/time/hrtimer.c:1868
 hrtimer_nanosleep+0x191/0x320 kernel/time/hrtimer.c:1924
 __do_sys_nanosleep kernel/time/hrtimer.c:1958 [inline]
 __se_sys_nanosleep kernel/time/hrtimer.c:1945 [inline]
 __x64_sys_nanosleep+0x106/0x150 kernel/time/hrtimer.c:1945
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880a64b9514 of 2 bytes by task 7855 on cpu 0:
 bio_set_flag include/linux/bio.h:239 [inline]
 blk_throtl_bio+0x113/0x1830 block/blk-throttle.c:2217
 blkcg_bio_issue_check include/linux/blk-cgroup.h:745 [inline]
 generic_make_request_checks+0x6ef/0x1130 block/blk-core.c:962
 generic_make_request+0x3e/0x740 block/blk-core.c:1018
 __blk_queue_split+0x767/0xb40 block/blk-merge.c:332
 blk_mq_make_request+0x104/0xf60 block/blk-mq.c:1959
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 ext4_io_submit+0xdf/0x110 fs/ext4/page-io.c:348
 io_submit_add_bh fs/ext4/page-io.c:388 [inline]
 ext4_bio_write_page+0x476/0xb90 fs/ext4/page-io.c:503
 mpage_submit_page+0xe4/0x1a0 fs/ext4/inode.c:2222
 mpage_map_and_submit_buffers+0x331/0x520 fs/ext4/inode.c:2422
 mpage_map_and_submit_extent fs/ext4/inode.c:2556 [inline]
 ext4_writepages+0x1458/0x2300 fs/ext4/inode.c:2869
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __writeback_single_inode+0xaf/0x8e0 fs/fs-writeback.c:1452
 writeback_sb_inodes+0x4ba/0xa50 fs/fs-writeback.c:1716
 __writeback_inodes_wb+0xe8/0x1b0 fs/fs-writeback.c:1785
 wb_writeback+0x557/0x6a0 fs/fs-writeback.c:1894
 wb_check_background_flush fs/fs-writeback.c:1962 [inline]
 wb_do_writeback fs/fs-writeback.c:2050 [inline]
 wb_workfn+0x696/0x970 fs/fs-writeback.c:2078
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7855 Comm: kworker/u4:5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-8:0)
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