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BUG: KCSAN: data-race in __blk_queue_split / bio_endio

read to 0xffff888100cded14 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
 preempt_count arch/x86/include/asm/preempt.h:26 [inline]
 check_kcov_mode kernel/kcov.c:68 [inline]
 __sanitizer_cov_trace_pc+0x14/0x50 kernel/kcov.c:102
 __read_once_size+0x41/0xe0 include/linux/compiler.h:230
 PageTail include/linux/page-flags.h:183 [inline]
 PageCompound include/linux/page-flags.h:188 [inline]
 PageHuge+0xfe/0x140 mm/hugetlb.c:1369
 page_remove_file_rmap mm/rmap.c:1221 [inline]
 page_remove_rmap+0x1f7/0x770 mm/rmap.c:1305
 zap_pte_range mm/memory.c:1062 [inline]
 zap_pmd_range mm/memory.c:1166 [inline]
 zap_pud_range mm/memory.c:1195 [inline]
 zap_p4d_range mm/memory.c:1216 [inline]
 unmap_page_range+0xbab/0x18d0 mm/memory.c:1237
 unmap_single_vma+0x144/0x200 mm/memory.c:1282
 unmap_vmas+0xda/0x1a0 mm/memory.c:1314
 exit_mmap+0x13e/0x300 mm/mmap.c:3161
 __mmput kernel/fork.c:1079 [inline]
 mmput+0xea/0x280 kernel/fork.c:1100
 exit_mm kernel/exit.c:485 [inline]
 do_exit+0x4c9/0x18f0 kernel/exit.c:804
 do_group_exit+0xb4/0x1c0 kernel/exit.c:921
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x2f/0x6c0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888100cded14 of 2 bytes by task 28 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
 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
 wb_writeback+0x1f9/0x6a0 fs/fs-writeback.c:1892
 wb_do_writeback fs/fs-writeback.c:2037 [inline]
 wb_workfn+0x22e/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: 28 Comm: kworker/u4:2 Not tainted 5.4.0-rc7+ #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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