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BUG: KCSAN: data-race in find_get_pages_range_tag / xas_clear_mark

write to 0xffff88810dfb4fa8 of 8 bytes by task 10015 on cpu 1:
 instrument_write include/linux/instrumented.h:42 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:79 [inline]
 __test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:109 [inline]
 node_clear_mark lib/xarray.c:100 [inline]
 xas_clear_mark+0xa1/0x180 lib/xarray.c:911
 __test_set_page_writeback+0x3c3/0x4f0 mm/page-writeback.c:2800
 ext4_bio_write_page+0xfe/0xe60 fs/ext4/page-io.c:450
 mpage_submit_page fs/ext4/inode.c:2101 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2349 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2488 [inline]
 ext4_writepages+0xec2/0x1e70 fs/ext4/inode.c:2801
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 __filemap_fdatawrite mm/filemap.c:432 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:459
 ext4_alloc_da_blocks+0x4a/0x100 fs/ext4/inode.c:3165
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x263/0x4f0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x17c/0x1b0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810dfb4fa8 of 8 bytes by task 10031 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1660 [inline]
 xas_next_marked include/linux/xarray.h:1691 [inline]
 find_get_pages_range_tag+0x35c/0x600 mm/filemap.c:2109
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1122
 mpage_prepare_extent_to_map+0x195/0x640 fs/ext4/inode.c:2578
 ext4_writepages+0x674/0x1e70 fs/ext4/inode.c:2755
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 __filemap_fdatawrite mm/filemap.c:432 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:459
 ext4_alloc_da_blocks+0x4a/0x100 fs/ext4/inode.c:3165
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x263/0x4f0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:140
 get_signal+0x149f/0x14e0 kernel/signal.c:2554
 arch_do_signal_or_restart+0x2a/0x270 arch/x86/kernel/signal.c:811
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x11a/0x1b0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10031 Comm: syz-executor.2 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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