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BUG: KCSAN: data-race in __blk_queue_split / bio_endio

read to 0xffff888124998614 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+0xa6/0x180 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x19
 should_watch kernel/kcsan/core.c:167 [inline]
 __kcsan_setup_watchpoint+0x81/0x4a0 kernel/kcsan/core.c:307
 __tsan_write1 kernel/kcsan/kcsan.c:33 [inline]
 __tsan_write1+0x32/0x40 kernel/kcsan/kcsan.c:33
 kallsyms_expand_symbol.constprop.0+0xe8/0x160 kernel/kallsyms.c:87

write to 0xffff888124998614 of 2 bytes by task 2685 on cpu 0:
 bio_set_flag include/linux/bio.h:239 [inline]
 __blk_queue_split+0x726/0xb40 block/blk-merge.c:328
 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
 ext4_writepages+0xea9/0x2300 fs/ext4/inode.c:2899
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __writeback_single_inode+0xaf/0x8e0 fs/fs-writeback.c:1449
 writeback_sb_inodes+0x4ba/0xa50 fs/fs-writeback.c:1713
 __writeback_inodes_wb+0xe8/0x1b0 fs/fs-writeback.c:1782
 wb_writeback+0x557/0x6a0 fs/fs-writeback.c:1891
 wb_check_old_data_flush fs/fs-writeback.c:1993 [inline]
 wb_do_writeback fs/fs-writeback.c:2046 [inline]
 wb_workfn+0x7bb/0x970 fs/fs-writeback.c:2075
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2685 Comm: kworker/u4:4 Not tainted 5.4.0-rc3+ #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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