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BUG: KCSAN: data-race in __filemap_fdatawrite_range / __xa_clear_mark

write to 0xffff8880bad54e2c of 4 bytes by interrupt on cpu 1:
 xa_mark_clear lib/xarray.c:75 [inline]
 xas_clear_mark lib/xarray.c:918 [inline]
 __xa_clear_mark+0x325/0x350 lib/xarray.c:1726
 test_clear_page_writeback+0x28d/0x480 mm/page-writeback.c:2739
 end_page_writeback+0xa7/0x110 mm/filemap.c:1369
 page_endio+0x1aa/0x1e0 mm/filemap.c:1400
 mpage_end_io+0x186/0x1d0 fs/mpage.c:54
 bio_endio+0x28a/0x370 block/bio.c:1449
 req_bio_endio block/blk-core.c:259 [inline]
 blk_update_request+0x535/0xbd0 block/blk-core.c:1577
 blk_mq_end_request+0x22/0x50 block/blk-mq.c:562
 lo_complete_rq+0xca/0x180 drivers/block/loop.c:500
 blk_done_softirq+0x1a5/0x200 block/blk-mq.c:586
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 run_ksoftirqd+0x2f/0x60 kernel/softirq.c:652
 smpboot_thread_fn+0x347/0x530 kernel/smpboot.c:165
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8880bad54e2c of 4 bytes by task 10400 on cpu 0:
 xa_marked include/linux/xarray.h:416 [inline]
 mapping_tagged include/linux/fs.h:493 [inline]
 __filemap_fdatawrite_range+0x113/0x1d0 mm/filemap.c:418
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:655
 generic_file_direct_write+0xb7/0x3e0 mm/filemap.c:3278
 __generic_file_write_iter+0x19c/0x330 mm/filemap.c:3489
 generic_file_write_iter+0x2f3/0x3e0 mm/filemap.c:3564
 call_write_iter include/linux/fs.h:1882 [inline]
 do_iter_readv_writev+0x32e/0x3d0 fs/read_write.c:713
 do_iter_write+0x112/0x4b0 fs/read_write.c:1018
 vfs_iter_write+0x4c/0x70 fs/read_write.c:1059
 iter_file_splice_write+0x41a/0x770 fs/splice.c:750
 do_splice_from fs/splice.c:846 [inline]
 direct_splice_actor+0x95/0x160 fs/splice.c:1016
 splice_direct_to_actor+0x365/0x660 fs/splice.c:971
 do_splice_direct+0xf2/0x170 fs/splice.c:1059
 do_sendfile+0x56a/0xba0 fs/read_write.c:1540
 __do_sys_sendfile64 fs/read_write.c:1601 [inline]
 __se_sys_sendfile64 fs/read_write.c:1587 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1587
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10400 Comm: syz-executor.4 Not tainted 5.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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