[CentOS] Writing to a symlink on a read-only file system that land on a read-write file system

James Pearson wrote:
> We've come across a problem with 6.4 kernels that we didn't have with 
> 6.2 kernels - which involves writing to a symlink that is on a read-only 
> file system - but the symlink lands on a read-write file system
> 
> The following shows the issue:
> 
>   mkdir -p /mnt/tmp
>   mount -t tmpfs -o size=1% none /mnt/tmp
>   rm -f /tmp/file
>   ln -s /tmp/file /mnt/tmp/file
>   mount -o remount,ro /mnt/tmp
>   echo "some text" > /mnt/tmp/file
> 
> On a machine with a 6.2 kernel, the above works fine - the target of the 
> symlink (/tmp/file) is created etc. with no error
> 
> But on a machine with a 6.4 kernel, the above fails with:
> 
>   /mnt/tmp/file: Read-only file system.

Looks like this is known bug with 6.4 - and hopefully should be fixed in 
some later 'zstream' release

James Pearson