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BUG: KCSAN: data-race in find_group_orlov / percpu_counter_add_batch

write to 0xffff8882186950e0 of 8 bytes by task 25450 on cpu 1:
 percpu_counter_add_batch+0xbc/0x140 lib/percpu_counter.c:91
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 percpu_counter_sub include/linux/percpu_counter.h:189 [inline]
 ext4_mb_mark_diskspace_used+0x532/0xa00 fs/ext4/mballoc.c:3010
 ext4_mb_new_blocks+0x714/0x1ea0 fs/ext4/mballoc.c:4560
 ext4_ext_map_blocks+0x1a5c/0x20f0 fs/ext4/extents.c:4440
 ext4_map_blocks+0x230/0xcf0 fs/ext4/inode.c:622
 ext4_alloc_file_blocks+0x22f/0x6f0 fs/ext4/extents.c:4629
 ext4_fallocate+0x9ec/0x2240 fs/ext4/extents.c:4910
 vfs_fallocate+0x3b1/0x650 fs/open.c:309
 ioctl_preallocate+0x12a/0x190 fs/ioctl.c:504
 file_ioctl fs/ioctl.c:544 [inline]
 do_vfs_ioctl+0xa6b/0xd00 fs/ioctl.c:742
 ksys_ioctl+0xb2/0x150 fs/ioctl.c:761
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8882186950e0 of 8 bytes by task 7786 on cpu 0:
 find_group_orlov+0x159/0x890 fs/ext4/ialloc.c:441
 __ext4_new_inode+0xb04/0x2f30 fs/ext4/ialloc.c:869
 ext4_mkdir+0x272/0x820 fs/ext4/namei.c:2782
 vfs_mkdir+0x281/0x390 fs/namei.c:3889
 do_mkdirat+0x1b5/0x200 fs/namei.c:3912
 __do_sys_mkdir fs/namei.c:3928 [inline]
 __se_sys_mkdir fs/namei.c:3926 [inline]
 __x64_sys_mkdir+0x3d/0x50 fs/namei.c:3926
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7786 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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