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BUG: KCSAN: data-race in find_group_orlov / percpu_counter_add_batch

write to 0xffff8882181d6908 of 8 bytes by task 13286 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_dec include/linux/percpu_counter.h:184 [inline]
 __ext4_new_inode+0x14a0/0x2f30 fs/ext4/ialloc.c:1074
 ext4_symlink+0x322/0x9e0 fs/ext4/namei.c:3287
 vfs_symlink fs/namei.c:4201 [inline]
 vfs_symlink+0x216/0x310 fs/namei.c:4187
 do_symlinkat+0x1ac/0x1e0 fs/namei.c:4228
 __do_sys_symlink fs/namei.c:4247 [inline]
 __se_sys_symlink fs/namei.c:4245 [inline]
 __x64_sys_symlink+0x3c/0x50 fs/namei.c:4245
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8882181d6908 of 8 bytes by task 7889 on cpu 0:
 find_group_orlov+0x12c/0x890 fs/ext4/ialloc.c:439
 __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: 7889 Comm: syz-executor.4 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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