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BUG: KCSAN: data-race in __filemap_fdatawrite_range / xas_clear_mark

write to 0xffff8880bb0a846c of 4 bytes by task 22003 on cpu 0:
 xa_mark_clear lib/xarray.c:75 [inline]
 xas_clear_mark+0x15a/0x170 lib/xarray.c:918
 __test_set_page_writeback+0x35f/0x420 mm/page-writeback.c:2808
 ext4_bio_write_page+0xc7/0xcd0 fs/ext4/page-io.c:451
 mpage_submit_page+0xf4/0x170 fs/ext4/inode.c:2082
 mpage_process_page_bufs+0x38a/0x420 fs/ext4/inode.c:2196
 mpage_prepare_extent_to_map+0x497/0x600 fs/ext4/inode.c:2608
 ext4_writepages+0x7e2/0x1cb0 fs/ext4/inode.c:2736
 do_writepages+0x7b/0x150 mm/page-writeback.c:2354
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:421
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:760
 ext4_sync_file+0xe2/0x680 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2882 [inline]
 ext4_buffered_write_iter+0x34e/0x390 fs/ext4/file.c:277
 ext4_file_write_iter+0x4a3/0xfd0 fs/ext4/file.c:498
 call_write_iter include/linux/fs.h:1907 [inline]
 do_iter_readv_writev+0x321/0x3c0 fs/read_write.c:694
 do_iter_write+0x10e/0x470 fs/read_write.c:999
 vfs_iter_write+0x4c/0x70 fs/read_write.c:1040
 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+0x562/0xb10 fs/read_write.c:1521
 __do_sys_sendfile64 fs/read_write.c:1582 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1568
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bb0a846c of 4 bytes by task 21994 on cpu 1:
 xa_marked include/linux/xarray.h:416 [inline]
 mapping_tagged include/linux/fs.h:523 [inline]
 __filemap_fdatawrite_range+0x113/0x1d0 mm/filemap.c:417
 filemap_write_and_wait_range+0x8b/0x230 mm/filemap.c:654
 iomap_dio_rw+0x399/0x8c0 fs/iomap/direct-io.c:474
 ext4_dio_write_iter fs/ext4/file.c:545 [inline]
 ext4_file_write_iter+0xd61/0xfd0 fs/ext4/file.c:653
 call_write_iter include/linux/fs.h:1907 [inline]
 do_iter_readv_writev+0x321/0x3c0 fs/read_write.c:694
 do_iter_write+0x10e/0x470 fs/read_write.c:999
 vfs_iter_write+0x4c/0x70 fs/read_write.c:1040
 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+0x562/0xb10 fs/read_write.c:1521
 __do_sys_sendfile64 fs/read_write.c:1582 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1568
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 21994 Comm: syz-executor.2 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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