linux-ext4 - How to create new file in idmapped mountpoint

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Message-ID: <e4f9392e-b5b6-4063-aecb-4d034c5d2bb6@huawei.com>
Date: Fri, 14 Jun 2024 15:09:22 +0800
From: Hongbo Li <lihongbo22@...wei.com>
To: <linux-ext4@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: How to create new file in idmapped mountpoint

Hi everyone !

How can I create new file in idmapped mountpoint in ext4?

I try to do the following test:
```
losetup /dev/loop1 ext4.img
mkfs.ext4 /dev/loop1
mount /dev/loop1 /mnt/ext4
./mount-idmapped --map-mount b:0:1001:1 /mnt/ext4 /mnt/idmapped1
cp testfile /mnt/idmapped1
```
then it rebacks me:
```
cp: cannot create regular file '/mnt/idmapped1/testfile': Value too 
large for defined data type
```
Did I use it incorrectly?

Thanks,
Hongbo.