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BUG: KCSAN: data-race in mb_mark_used / mb_update_avg_fragment_size

write to 0xffff88810046c854 of 4 bytes by task 2109 on cpu 1:
 mb_mark_used+0x13b/0xc50 fs/ext4/mballoc.c:1943
 ext4_mb_use_best_found+0x102/0x320 fs/ext4/mballoc.c:2015
 ext4_mb_simple_scan_group+0x253/0x3a0 fs/ext4/mballoc.c:2293
 ext4_mb_regular_allocator+0x1974/0x2520 fs/ext4/mballoc.c:2755
 ext4_mb_new_blocks+0x762/0x1f90 fs/ext4/mballoc.c:5515
 ext4_alloc_branch fs/ext4/indirect.c:333 [inline]
 ext4_ind_map_blocks+0xaab/0x1620 fs/ext4/indirect.c:626
 ext4_map_blocks+0x6d2/0xef0 fs/ext4/inode.c:640
 mpage_map_one_extent+0x10d/0x360 fs/ext4/inode.c:2395
 mpage_map_and_submit_extent fs/ext4/inode.c:2448 [inline]
 ext4_writepages+0xc1a/0x1d10 fs/ext4/inode.c:2800
 do_writepages+0x7b/0x150 mm/page-writeback.c:2355
 __filemap_fdatawrite_range mm/filemap.c:413 [inline]
 filemap_write_and_wait_range+0x20a/0x390 mm/filemap.c:686
 ext4_punch_hole+0x142/0x9a0 fs/ext4/inode.c:4020
 ext4_fallocate+0xea/0x4d0 fs/ext4/extents.c:4662
 vfs_fallocate+0x463/0x660 fs/open.c:311
 ksys_fallocate fs/open.c:334 [inline]
 __do_sys_fallocate fs/open.c:342 [inline]
 __se_sys_fallocate fs/open.c:340 [inline]
 __x64_sys_fallocate+0x75/0xc0 fs/open.c:340
 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 0xffff88810046c854 of 4 bytes by task 1767 on cpu 0:
 ext4_mb_avg_fragment_size_cmp fs/ext4/mballoc.c:835 [inline]
 ext4_mb_rb_insert fs/ext4/mballoc.c:811 [inline]
 mb_update_avg_fragment_size+0x184/0x260 fs/ext4/mballoc.c:859
 mb_free_blocks+0x9e4/0xb40 fs/ext4/mballoc.c:1856
 ext4_free_blocks+0x1418/0x1b50 fs/ext4/mballoc.c:5989
 ext4_remove_blocks+0x61a/0x800 fs/ext4/extents.c:2502
 ext4_ext_rm_leaf+0x670/0xd20 fs/ext4/extents.c:2668
 ext4_ext_remove_space+0x901/0x1300 fs/ext4/extents.c:2916
 ext4_ext_truncate+0xfe/0x170 fs/ext4/extents.c:4377
 ext4_truncate+0x76e/0xa80 fs/ext4/inode.c:4262
 ext4_evict_inode+0xa54/0xdb0 fs/ext4/inode.c:288
 evict+0x1c8/0x3c0 fs/inode.c:584
 iput_final fs/inode.c:1660 [inline]
 iput+0x430/0x580 fs/inode.c:1686
 dentry_unlink_inode+0x23a/0x260 fs/dcache.c:376
 d_delete+0x78/0xe0 fs/dcache.c:2505
 vfs_rmdir+0x2a6/0x2c0 fs/namei.c:3919
 do_rmdir+0x14a/0x2e0 fs/namei.c:3968
 __do_sys_rmdir fs/namei.c:3986 [inline]
 __se_sys_rmdir fs/namei.c:3984 [inline]
 __x64_sys_rmdir+0x2c/0x30 fs/namei.c:3984
 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: 0x00007dd0 -> 0x00007bd0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1767 Comm: syz-executor.4 Not tainted 5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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