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BUG: KCSAN: data-race in xas_find_marked / xas_init_marks

write to 0xffff88810f99bfb8 of 8 bytes by task 4224 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+0x213/0xd00 lib/xarray.c:803
 page_cache_delete_batch mm/filemap.c:337 [inline]
 delete_from_page_cache_batch+0x41e/0x830 mm/filemap.c:358
 truncate_inode_pages_range+0x492/0xf10 mm/truncate.c:366
 truncate_pagecache_range+0x80/0x90 mm/truncate.c:931
 ext4_zero_range+0x421/0xa30 fs/ext4/extents.c:4577
 ext4_fallocate+0x214/0x560 fs/ext4/extents.c:4672
 vfs_fallocate+0x43c/0x5d0 fs/open.c:309
 ksys_fallocate fs/open.c:332 [inline]
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x75/0xc0 fs/open.c:338
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810f99bfb8 of 8 bytes by task 4219 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1625 [inline]
 xas_find_marked+0x22f/0x6b0 lib/xarray.c:1198
 find_get_pages_range_tag+0xa3/0x580 mm/filemap.c:1976
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1120
 mpage_prepare_extent_to_map+0x19c/0x650 fs/ext4/inode.c:2559
 ext4_writepages+0x97d/0x1ef0 fs/ext4/inode.c:2780
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:422
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 ext4_sync_file+0xfc/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2734 [inline]
 ext4_buffered_write_iter+0x369/0x3b0 fs/ext4/file.c:277
 ext4_file_write_iter+0x57b/0x1000 fs/ext4/file.c:498
 call_write_iter include/linux/fs.h:1872 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x665/0x6f0 fs/read_write.c:578
 ksys_write+0xce/0x180 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 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: 4219 Comm: syz-executor.1 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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