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BUG: KCSAN: data-race in mb_free_blocks / mb_update_avg_fragment_size

write to 0xffff8881018c66d4 of 4 bytes by task 1800 on cpu 0:
 mb_free_blocks+0x156/0xb40 fs/ext4/mballoc.c:1802
 ext4_free_blocks+0x1448/0x1b80 fs/ext4/mballoc.c:6061
 ext4_remove_blocks+0x61a/0x800 fs/ext4/extents.c:2506
 ext4_ext_rm_leaf+0x684/0xd40 fs/ext4/extents.c:2672
 ext4_ext_remove_space+0x8d6/0x1290 fs/ext4/extents.c:2920
 ext4_ext_truncate+0xfe/0x170 fs/ext4/extents.c:4382
 ext4_truncate+0x76e/0xa80 fs/ext4/inode.c:4268
 ext4_evict_inode+0xa54/0xdb0 fs/ext4/inode.c:287
 evict+0x1c8/0x3c0 fs/inode.c:586
 iput_final fs/inode.c:1662 [inline]
 iput+0x430/0x580 fs/inode.c:1688
 do_unlinkat+0x2a4/0x520 fs/namei.c:4174
 __do_sys_unlink fs/namei.c:4215 [inline]
 __se_sys_unlink fs/namei.c:4213 [inline]
 __x64_sys_unlink+0x2c/0x30 fs/namei.c:4213
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881018c66d4 of 4 bytes by task 1789 on cpu 1:
 ext4_mb_avg_fragment_size_cmp fs/ext4/mballoc.c:839 [inline]
 ext4_mb_rb_insert fs/ext4/mballoc.c:815 [inline]
 mb_update_avg_fragment_size+0x184/0x260 fs/ext4/mballoc.c:863
 mb_mark_used+0xae0/0xc50 fs/ext4/mballoc.c:1998
 ext4_mb_use_best_found+0x102/0x320 fs/ext4/mballoc.c:2019
 ext4_mb_measure_extent fs/ext4/mballoc.c:2135 [inline]
 ext4_mb_complex_scan_group+0x349/0x850 fs/ext4/mballoc.c:2365
 ext4_mb_regular_allocator+0x1a22/0x2520 fs/ext4/mballoc.c:2778
 ext4_mb_new_blocks+0x762/0x1f90 fs/ext4/mballoc.c:5586
 ext4_ext_map_blocks+0x1579/0x1f10 fs/ext4/extents.c:4250
 ext4_map_blocks+0x70d/0xef0 fs/ext4/inode.c:637
 ext4_getblk+0xb5/0x3d0 fs/ext4/inode.c:847
 ext4_bread+0x28/0x100 fs/ext4/inode.c:900
 ext4_append+0xd1/0x1c0 fs/ext4/namei.c:67
 ext4_init_new_dir+0x177/0x500 fs/ext4/namei.c:2893
 ext4_mkdir+0x329/0x760 fs/ext4/namei.c:2939
 vfs_mkdir+0x2c3/0x3e0 fs/namei.c:3885
 do_mkdirat+0x12e/0x2e0 fs/namei.c:3911
 __do_sys_mkdir fs/namei.c:3931 [inline]
 __se_sys_mkdir fs/namei.c:3929 [inline]
 __x64_sys_mkdir+0x40/0x50 fs/namei.c:3929
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00003620 -> 0x000037d2

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1789 Comm: syz-executor.1 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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