[PATCH 4/6] xfs: use memdup_user()

[Li Zefan]

Roland Dreier wrote:
>  > wouldn't NULL be a better error return for this kind of interface,
>  > matching kmalloc?
> 
> I guess returning an error code from memdup_user() lets callers
> distinguish between ENOMEM and EFAULT.  Not sure if that's important or
> not but there probably are at least some sites that care.
> 

Right, and this API is simlilar to strndup_user().