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BUG: KCSAN: data-race in ext4_writepages / xas_clear_mark

write to 0xffff88800d2b4c44 of 4 bytes by task 26530 on cpu 0:
 xa_mark_clear lib/xarray.c:75 [inline]
 xas_clear_mark+0x15a/0x170 lib/xarray.c:921
 __test_set_page_writeback+0x3bd/0x5b0 mm/page-writeback.c:2808
 ext4_bio_write_page+0xef/0xda0 fs/ext4/page-io.c:453
 mpage_submit_page fs/ext4/inode.c:2092 [inline]
 mpage_process_page_bufs+0x4f8/0x5e0 fs/ext4/inode.c:2206
 mpage_prepare_extent_to_map+0x4d6/0x630 fs/ext4/inode.c:2618
 ext4_writepages+0x674/0x1e30 fs/ext4/inode.c:2746
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:655
 __iomap_dio_rw+0x38c/0x9b0 fs/iomap/direct-io.c:489
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:605
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x3bd/0x420 fs/ext4/file.c:129
 call_read_iter include/linux/fs.h:1881 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:788 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:867
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x574/0xb70 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800d2b4c44 of 4 bytes by task 26539 on cpu 1:
 xa_marked include/linux/xarray.h:416 [inline]
 mapping_tagged include/linux/fs.h:488 [inline]
 ext4_writepages+0x150/0x1e30 fs/ext4/inode.c:2660
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:655
 __iomap_dio_rw+0x38c/0x9b0 fs/iomap/direct-io.c:489
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:605
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x3bd/0x420 fs/ext4/file.c:129
 call_read_iter include/linux/fs.h:1881 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:788 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:867
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x574/0xb70 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 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: 1 PID: 26539 Comm: syz-executor.4 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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