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BUG: KCSAN: data-race in mb_free_blocks / mb_update_avg_fragment_size

write to 0xffff8881013cf0d8 of 4 bytes by task 18927 on cpu 0:
 mb_free_blocks+0x323/0xb40 fs/ext4/mballoc.c:1833
 ext4_free_blocks+0x1418/0x1b50 fs/ext4/mballoc.c:5988
 ext4_remove_blocks+0x61a/0x800 fs/ext4/extents.c:2498
 ext4_ext_rm_leaf+0x670/0xd20 fs/ext4/extents.c:2664
 ext4_ext_remove_space+0x901/0x1300 fs/ext4/extents.c:2912
 ext4_ext_truncate+0xfe/0x170 fs/ext4/extents.c:4373
 ext4_truncate+0x76e/0xa80 fs/ext4/inode.c:4262
 ext4_truncate_failed_write fs/ext4/truncate.h:20 [inline]
 ext4_da_write_begin+0x56e/0x820 fs/ext4/inode.c:3029
 generic_perform_write+0x196/0x3a0 mm/filemap.c:3660
 ext4_buffered_write_iter+0x2f2/0x3f0 fs/ext4/file.c:269
 ext4_file_write_iter+0x2e7/0x11d0 fs/ext4/file.c:519
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881013cf0d8 of 4 bytes by task 18930 on cpu 1:
 ext4_mb_avg_fragment_size_cmp fs/ext4/mballoc.c:834 [inline]
 ext4_mb_rb_insert fs/ext4/mballoc.c:811 [inline]
 mb_update_avg_fragment_size+0x161/0x260 fs/ext4/mballoc.c:859
 mb_mark_used+0xae0/0xc50 fs/ext4/mballoc.c:1993
 ext4_mb_use_best_found+0x102/0x320 fs/ext4/mballoc.c:2014
 ext4_mb_simple_scan_group+0x253/0x3a0 fs/ext4/mballoc.c:2292
 ext4_mb_regular_allocator+0x1974/0x2520 fs/ext4/mballoc.c:2754
 ext4_mb_new_blocks+0x762/0x1f90 fs/ext4/mballoc.c:5514
 ext4_ext_map_blocks+0x1569/0x1f00 fs/ext4/extents.c:4241
 ext4_map_blocks+0x70d/0xef0 fs/ext4/inode.c:638
 ext4_alloc_file_blocks+0x271/0x720 fs/ext4/extents.c:4428
 ext4_fallocate+0x2a7/0x4d0 fs/ext4/extents.c:4708
 vfs_fallocate+0x463/0x660 fs/open.c:311
 file_ioctl fs/ioctl.c:497 [inline]
 do_vfs_ioctl+0x1322/0x1410 fs/ioctl.c:1048
 __do_sys_ioctl fs/ioctl.c:1067 [inline]
 __se_sys_ioctl+0x83/0x140 fs/ioctl.c:1055
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:1055
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18930 Comm: syz-executor.4 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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