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BUG: KCSAN: data-race in bio_chain / bio_endio

read to 0xffff888115714614 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
 __kcsan_check_watchpoint+0x30/0x180 kernel/kcsan/core.c:252
 __tsan_read8+0x15/0x30 kernel/kcsan/kcsan.c:36
 compound_head include/linux/page-flags.h:174 [inline]
 PageSwapCache include/linux/page-flags.h:383 [inline]
 free_swap_cache mm/swap_state.c:267 [inline]
 free_pages_and_swap_cache+0xa1/0x2a0 mm/swap_state.c:295

write to 0xffff888115714614 of 2 bytes by task 29871 on cpu 0:
 bio_set_flag include/linux/bio.h:239 [inline]
 bio_inc_remaining include/linux/bio.h:689 [inline]
 bio_chain+0x86/0xb0 block/bio.c:333
 __blk_queue_split+0x745/0xb40 block/blk-merge.c:330
 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]
 do_blockdev_direct_IO+0x64e1/0x78c0 fs/direct-io.c:1353
 __blockdev_direct_IO+0x86/0xa0 fs/direct-io.c:1412
 ext4_direct_IO_write fs/ext4/inode.c:3742 [inline]
 ext4_direct_IO+0x6f5/0xf70 fs/ext4/inode.c:3871
 generic_file_direct_write+0x14d/0x2e0 mm/filemap.c:3207
 __generic_file_write_iter+0x17e/0x380 mm/filemap.c:3390
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [inline]
 aio_write+0x1de/0x2d0 fs/aio.c:1583
 __io_submit_one fs/aio.c:1815 [inline]
 io_submit_one+0x639/0xe70 fs/aio.c:1862

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29871 Comm: syz-executor.3 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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