==================================================================
BUG: KCSAN: data-race in ext4_nonda_switch / percpu_counter_add_batch

read to 0xffff8881264b9958 of 8 bytes by task 12141 on cpu 1:
 ext4_nonda_switch+0x5a/0x140 fs/ext4/inode.c:2990
 ext4_da_write_begin+0xc5/0x7e0 fs/ext4/inode.c:3036
 generic_perform_write+0x136/0x320 mm/filemap.c:3304
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3433
 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:1815 [inline]
 io_submit_one+0x639/0xe70 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

write to 0xffff8881264b9958 of 8 bytes by task 12115 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_claim_free_clusters+0x68/0x90 fs/ext4/balloc.c:599
 ext4_da_reserve_space+0x102/0x280 fs/ext4/inode.c:1612
 ext4_insert_delayed_block fs/ext4/inode.c:1780 [inline]
 ext4_da_map_blocks fs/ext4/inode.c:1895 [inline]
 ext4_da_get_block_prep+0x87f/0xa60 fs/ext4/inode.c:1959
 ext4_block_write_begin+0x33e/0xba0 fs/ext4/inode.c:1202
 ext4_da_write_begin+0x1da/0x7e0 fs/ext4/inode.c:3094
 generic_perform_write+0x136/0x320 mm/filemap.c:3304
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3433
 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:1815 [inline]
 io_submit_one+0x639/0xe70 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12115 Comm: syz-executor.4 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================