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BUG: KCSAN: data-race in ext4_itable_unused_count / ext4_itable_unused_set

write to 0xffff88814453f03c of 2 bytes by task 14024 on cpu 1:
 ext4_itable_unused_set+0x1b/0x80 fs/ext4/super.c:403
 __ext4_new_inode+0x1ba8/0x3060 fs/ext4/ialloc.c:1200
 ext4_symlink+0x2bc/0x780 fs/ext4/namei.c:3336
 vfs_symlink+0x216/0x2d0 fs/namei.c:3962
 do_symlinkat+0xee/0x280 fs/namei.c:3989
 __do_sys_symlink fs/namei.c:4008 [inline]
 __se_sys_symlink fs/namei.c:4006 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4006
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88814453f03c of 2 bytes by task 14023 on cpu 0:
 ext4_itable_unused_count+0x18/0x80 fs/ext4/super.c:347
 __ext4_get_inode_loc+0x691/0x920 fs/ext4/inode.c:4405
 ext4_get_inode_loc fs/ext4/inode.c:4457 [inline]
 ext4_reserve_inode_write+0xb8/0x1f0 fs/ext4/inode.c:5744
 __ext4_mark_inode_dirty+0x6f/0x5d0 fs/ext4/inode.c:5911
 ext4_ext_tree_init+0x7e/0x90 fs/ext4/extents.c:828
 __ext4_new_inode+0x2a90/0x3060 fs/ext4/ialloc.c:1326
 ext4_symlink+0x2bc/0x780 fs/ext4/namei.c:3336
 vfs_symlink+0x216/0x2d0 fs/namei.c:3962
 do_symlinkat+0xee/0x280 fs/namei.c:3989
 __do_sys_symlink fs/namei.c:4008 [inline]
 __se_sys_symlink fs/namei.c:4006 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4006
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 14023 Comm: syz-executor.5 Not tainted 5.11.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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