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BUG: KCSAN: data-race in alloc_empty_file / percpu_counter_add_batch

write to 0xffffffff85c08588 of 8 bytes by task 14678 on cpu 0:
 percpu_counter_add_batch+0xca/0x150 lib/percpu_counter.c:91
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 percpu_counter_inc include/linux/percpu_counter.h:179 [inline]
 alloc_empty_file+0xd2/0x180 fs/file_table.c:153
 alloc_file+0x4e/0x2b0 fs/file_table.c:193
 alloc_file_pseudo+0x11c/0x1b0 fs/file_table.c:232
 anon_inode_getfile fs/anon_inodes.c:91 [inline]
 anon_inode_getfile+0x103/0x1d0 fs/anon_inodes.c:74
 __do_sys_perf_event_open+0xdb9/0x1e50 kernel/events/core.c:11401
 __se_sys_perf_event_open kernel/events/core.c:11160 [inline]
 __x64_sys_perf_event_open+0x70/0x90 kernel/events/core.c:11160
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff85c08588 of 8 bytes by task 9051 on cpu 1:
 get_nr_files fs/file_table.c:66 [inline]
 alloc_empty_file+0x2d/0x180 fs/file_table.c:142
 alloc_file+0x4e/0x2b0 fs/file_table.c:193
 alloc_file_pseudo+0x11c/0x1b0 fs/file_table.c:232
 anon_inode_getfile fs/anon_inodes.c:91 [inline]
 anon_inode_getfile+0x103/0x1d0 fs/anon_inodes.c:74
 do_epoll_create+0x23c/0x320 fs/eventpoll.c:2041
 __do_sys_epoll_create1 fs/eventpoll.c:2060 [inline]
 __se_sys_epoll_create1 fs/eventpoll.c:2058 [inline]
 __x64_sys_epoll_create1+0x28/0x40 fs/eventpoll.c:2058
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9051 Comm: udevd 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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