Re: [PATCH 05/22][RFC] Unionfs: Copyup Functionality

[Jan Engelhardt <jengelh@linux01.gwdg.de>]

>> >> Is BUG the right thing, what do others think? (Using WARN, and set err to
>> >> something useful?)
>> > 
>> >Well, it is definitely a condition which Unionfs doesn't expect - if it
>> >doesn't know about the type, how could it copy it up?
>> 
>> Other filesystems don't seem to BUG either (at least I have not run into 
>> that yet) when - for whatever reasons - the statdata of a dentry is 
>> fubared. `ls`  just displays it then, like
>> 
>>  ?-w---Sr-T 1 root root 4294967295 date fubared_file
>
>I was thinking about this, and the difference between "other filesystems"
>and unionfs in this case is that the example above is just stat. During
>copyup, unionfs has to copy the file to another filesystem. How is it
>supposed to do that when it doesn't understand what the file is?
>
>Sure, when unionfs does stat, fubared statdata is fine, but during
>copyup...bad things could potentially happen.
>
>Any suggestions how to copyup an unknown file type?

Return some error value if possible. -EIO, banners, big printk()s,
anything. Tell the user the filesytem on some branch is hosed - or
too advanced to be understood by unionfs. (There seems to be a
variety of file types in other UNIXes according to `man 2 stat`,
such as doors, etc.)



Jan Engelhardt
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