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BUG: KCSAN: data-race in ext4_nonda_switch / percpu_counter_add_batch

write to 0xffff8882187568e0 of 8 bytes by task 15092 on cpu 0:
 percpu_counter_add_batch+0xca/0x150 lib/percpu_counter.c:91
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 ext4_free_blocks+0xb4d/0x17e0 fs/ext4/mballoc.c:4928
 ext4_remove_blocks fs/ext4/extents.c:2678 [inline]
 ext4_ext_rm_leaf fs/ext4/extents.c:2831 [inline]
 ext4_ext_remove_space+0x1841/0x32c0 fs/ext4/extents.c:3076
 ext4_ext_truncate+0x120/0x130 fs/ext4/extents.c:4599
 ext4_truncate+0x5a2/0x990 fs/ext4/inode.c:4511
 ext4_truncate_failed_write fs/ext4/truncate.h:20 [inline]
 ext4_direct_IO_write fs/ext4/inode.c:3766 [inline]
 ext4_direct_IO+0xbfa/0xf70 fs/ext4/inode.c:3871
 generic_file_direct_write+0x14d/0x2e0 mm/filemap.c:3208
 __generic_file_write_iter+0x17e/0x380 mm/filemap.c:3391
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [inline]
 aio_write+0x1de/0x2d0 fs/aio.c:1583
 __io_submit_one fs/aio.c:1819 [inline]
 io_submit_one+0x461/0xe70 fs/aio.c:1862
 __do_sys_io_submit fs/aio.c:1921 [inline]
 __se_sys_io_submit fs/aio.c:1891 [inline]
 __x64_sys_io_submit+0x104/0x2d0 fs/aio.c:1891
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8882187568e0 of 8 bytes by task 15099 on cpu 1:
 ext4_nonda_switch+0x3d/0x140 fs/ext4/inode.c:2988
 ext4_da_write_begin+0xc5/0x7e0 fs/ext4/inode.c:3036
 generic_perform_write+0x136/0x320 mm/filemap.c:3305
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3434
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15099 Comm: syz-executor.1 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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