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BUG: KCSAN: data-race in find_get_pages_range_tag / xas_init_marks

write to 0xffff8880bb1b48e8 of 8 bytes by task 6119 on cpu 1:
 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+0x418/0x850 mm/filemap.c:358
 truncate_inode_pages_range+0x482/0xf70 mm/truncate.c:366
 truncate_pagecache_range+0x80/0x90 mm/truncate.c:931
 ext4_zero_range+0x421/0xa30 fs/ext4/extents.c:4571
 ext4_fallocate+0x214/0x560 fs/ext4/extents.c:4666
 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 0xffff8880bb1b48e8 of 8 bytes by task 6117 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1625 [inline]
 xas_next_marked include/linux/xarray.h:1656 [inline]
 find_get_pages_range_tag+0x30c/0x5b0 mm/filemap.c:1976
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1122
 mpage_prepare_extent_to_map+0x19c/0x650 fs/ext4/inode.c:2558
 ext4_writepages+0x97d/0x1ef0 fs/ext4/inode.c:2779
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:422
 __filemap_fdatawrite mm/filemap.c:430 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:457
 ext4_alloc_da_blocks+0x4c/0x130 fs/ext4/inode.c:3145
 ext4_release_file+0x5b/0x1c0 fs/ext4/file.c:142
 __fput+0x246/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 get_signal+0x11cf/0x1650 kernel/signal.c:2561
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:159 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:265
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6117 Comm: syz-executor.2 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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