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BUG: KCSAN: data-race in ext4_has_free_clusters / percpu_counter_add_batch

write to 0xffff8882183b0158 of 8 bytes by task 13771 on cpu 0:
 percpu_counter_add_batch+0xbc/0x140 lib/percpu_counter.c:91
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 ext4_claim_free_clusters+0x64/0x80 fs/ext4/balloc.c:602
 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_fallocate+0x9ec/0x2240 fs/ext4/extents.c:4910
 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

read to 0xffff8882183b0158 of 8 bytes by task 13768 on cpu 1:
 ext4_has_free_clusters+0x61/0x310 fs/ext4/balloc.c:558
 ext4_claim_free_clusters+0x2c/0x80 fs/ext4/balloc.c:601
 ext4_mb_new_blocks+0x18a/0x1ea0 fs/ext4/mballoc.c:4494
 ext4_new_meta_blocks+0x17e/0x210 fs/ext4/balloc.c:660
 ext4_ext_grow_indepth fs/ext4/extents.c:1276 [inline]
 ext4_ext_create_new_leaf fs/ext4/extents.c:1380 [inline]
 ext4_ext_insert_extent+0xab9/0x25d0 fs/ext4/extents.c:2053
 ext4_ext_map_blocks+0xbc7/0x20f0 fs/ext4/extents.c:4466
 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
 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: 1 PID: 13768 Comm: syz-executor.2 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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