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BUG: KCSAN: data-race in __blk_queue_split / bio_endio

read to 0xffff88812646c314 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
 get_current arch/x86/include/asm/current.h:15 [inline]
 __sanitizer_cov_trace_pc+0xd/0x50 kernel/kcov.c:101
 compound_head include/linux/page-flags.h:174 [inline]
 PageSwapBacked include/linux/page-flags.h:340 [inline]
 PageSwapCache include/linux/page-flags.h:385 [inline]
 free_swap_cache mm/swap_state.c:267 [inline]
 free_pages_and_swap_cache+0xd7/0x2a0 mm/swap_state.c:295
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:184 [inline]
 tlb_flush_mmu+0x72/0x3b0 mm/mmu_gather.c:191
 zap_pte_range mm/memory.c:1128 [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+0x1562/0x18d0 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 0xffff88812646c314 of 2 bytes by task 10977 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
 dio_bio_submit fs/direct-io.c:481 [inline]
 submit_page_section fs/direct-io.c:895 [inline]
 submit_page_section fs/direct-io.c:846 [inline]
 do_direct_IO fs/direct-io.c:1088 [inline]
 do_blockdev_direct_IO+0x63b2/0x78c0 fs/direct-io.c:1326
 __blockdev_direct_IO+0x86/0xa0 fs/direct-io.c:1412
 ext4_direct_IO_write fs/ext4/inode.c:3742 [inline]
 ext4_direct_IO+0x76c/0xfb0 fs/ext4/inode.c:3871
 generic_file_direct_write+0x14d/0x2e0 mm/filemap.c:3208
 __generic_file_write_iter+0x17e/0x380 mm/filemap.c:3391
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10977 Comm: syz-executor.1 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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