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BUG: KCSAN: data-race in ext4_has_free_clusters / percpu_counter_add_batch

write to 0xffff8882187258e0 of 8 bytes by task 7840 on cpu 1:
 percpu_counter_add_batch+0xbc/0x140 lib/percpu_counter.c:91
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 ext4_free_blocks+0xa06/0x1540 fs/ext4/mballoc.c:4932
 ext4_remove_blocks fs/ext4/extents.c:2646 [inline]
 ext4_ext_rm_leaf fs/ext4/extents.c:2812 [inline]
 ext4_ext_remove_space+0x1862/0x2bf0 fs/ext4/extents.c:3059
 ext4_ext_truncate+0x11a/0x120 fs/ext4/extents.c:4579
 ext4_truncate+0x5c8/0x9d0 fs/ext4/inode.c:4198
 ext4_evict_inode+0x5e6/0xa40 fs/ext4/inode.c:270
 evict+0x238/0x3f0 fs/inode.c:575
 iput_final fs/inode.c:1571 [inline]
 iput+0x36a/0x4d0 fs/inode.c:1597
 do_unlinkat+0x388/0x550 fs/namei.c:4143
 __do_sys_unlink fs/namei.c:4184 [inline]
 __se_sys_unlink fs/namei.c:4182 [inline]
 __x64_sys_unlink+0x38/0x50 fs/namei.c:4182
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8882187258e0 of 8 bytes by task 31028 on cpu 0:
 ext4_has_free_clusters+0x44/0x310 fs/ext4/balloc.c:557
 ext4_claim_free_clusters+0x2c/0x80 fs/ext4/balloc.c:601
 ext4_mb_new_blocks+0x18a/0x1ea0 fs/ext4/mballoc.c:4494
 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_zero_range fs/ext4/extents.c:4745 [inline]
 ext4_fallocate+0x1c37/0x2240 fs/ext4/extents.c:4878
 vfs_fallocate+0x3b1/0x650 fs/open.c:309
 ksys_fallocate+0x5b/0xa0 fs/open.c:332
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x59/0x70 fs/open.c:338
 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: 31028 Comm: syz-executor.3 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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