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BUG: KCSAN: data-race in filemap_flush / xas_init_marks

write to 0xffff88813f1f2334 of 4 bytes by task 4576 on cpu 0:
 xas_init_marks+0x2ee/0x340 lib/xarray.c:75
 xas_store+0x213/0xca0 lib/xarray.c:806
 page_cache_delete_batch mm/filemap.c:328 [inline]
 delete_from_page_cache_batch+0x375/0x690 mm/filemap.c:349
 truncate_inode_pages_range+0x1a5/0xa80 mm/truncate.c:329
 truncate_inode_pages mm/truncate.c:427 [inline]
 truncate_pagecache+0x4f/0x70 mm/truncate.c:741
 ext4_setattr+0xa21/0xec0 fs/ext4/inode.c:5498
 notify_change+0x8a3/0xa80 fs/attr.c:398
 do_truncate fs/open.c:64 [inline]
 do_sys_ftruncate+0x405/0x4c0 fs/open.c:196
 __do_sys_ftruncate fs/open.c:207 [inline]
 __se_sys_ftruncate fs/open.c:205 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:205
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813f1f2334 of 4 bytes by task 4572 on cpu 1:
 xa_marked include/linux/xarray.h:418 [inline]
 mapping_tagged include/linux/fs.h:489 [inline]
 __filemap_fdatawrite_range mm/filemap.c:409 [inline]
 __filemap_fdatawrite mm/filemap.c:421 [inline]
 filemap_flush+0xfc/0x160 mm/filemap.c:448
 ext4_alloc_da_blocks+0x4a/0xd0 fs/ext4/inode.c:3164
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x25b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 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+0x156/0x190 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+0x56/0x90 arch/x86/entry/common.c:57
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4572 Comm: syz-executor.3 Tainted: G        W         5.13.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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