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BUG: KCSAN: data-race in find_get_pages_range_tag / xas_init_marks

write to 0xffff888122851fa8 of 8 bytes by task 24667 on cpu 0:
 instrument_write include/linux/instrumented.h:42 [inline]
 __test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:85 [inline]
 node_clear_mark lib/xarray.c:100 [inline]
 xas_clear_mark lib/xarray.c:908 [inline]
 xas_init_marks+0x17e/0x310 lib/xarray.c:941
 xas_store+0x213/0xce0 lib/xarray.c:803
 page_cache_delete_batch mm/filemap.c:336 [inline]
 delete_from_page_cache_batch+0x3f7/0x7f0 mm/filemap.c:357
 truncate_inode_pages_range+0x472/0xef0 mm/truncate.c:366
 truncate_inode_pages mm/truncate.c:476 [inline]
 truncate_pagecache+0x4f/0x70 mm/truncate.c:817
 ext4_setattr+0xaea/0xeb0 fs/ext4/inode.c:5403
 notify_change+0x7d4/0xa20 fs/attr.c:336
 do_truncate fs/open.c:64 [inline]
 vfs_truncate+0x3f8/0x440 fs/open.c:110
 do_sys_truncate fs/open.c:133 [inline]
 __do_sys_truncate fs/open.c:145 [inline]
 __se_sys_truncate fs/open.c:143 [inline]
 __x64_sys_truncate+0xa0/0x120 fs/open.c:143
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888122851fa8 of 8 bytes by task 24638 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1625 [inline]
 xas_next_marked include/linux/xarray.h:1656 [inline]
 find_get_pages_range_tag+0x2fc/0x570 mm/filemap.c:1908
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1120
 mpage_prepare_extent_to_map+0x197/0x600 fs/ext4/inode.c:2559
 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
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:456
 ext4_alloc_da_blocks+0x4c/0x130 fs/ext4/inode.c:3146
 ext4_release_file+0x36/0x180 fs/ext4/file.c:142
 __fput+0x1df/0x460 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:123
 get_signal+0x14e2/0x1520 kernel/signal.c:2533
 do_signal+0x25/0x270 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:212 [inline]
 __prepare_exit_to_usermode+0x129/0x230 arch/x86/entry/common.c:246
 __syscall_return_slowpath arch/x86/entry/common.c:329 [inline]
 do_syscall_64+0xb9/0x120 arch/x86/entry/common.c:368
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24638 Comm: syz-executor.0 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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