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BUG: KCSAN: data-race in mb_mark_used / mb_update_avg_fragment_size

write to 0xffff888100478b54 of 4 bytes by task 1784 on cpu 0:
 mb_mark_used+0x13b/0xc50 fs/ext4/mballoc.c:1947
 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

read to 0xffff888100478b54 of 4 bytes by task 10314 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_free_blocks+0x9e4/0xb40 fs/ext4/mballoc.c:1860
 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_setattr+0xb00/0xef0 fs/ext4/inode.c:5521
 notify_change+0x8a3/0xac0 fs/attr.c:398
 do_truncate fs/open.c:64 [inline]
 do_sys_ftruncate+0x2d9/0x390 fs/open.c:192
 __do_sys_ftruncate fs/open.c:203 [inline]
 __se_sys_ftruncate fs/open.c:201 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:201
 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: 0x000050fa -> 0x000050f9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10314 Comm: syz-executor.4 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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