Re: [patch] readv/writev rework

[Hirokazu Takahashi]

Hello,

I appreciate for your kind answer.
I understand clearly.
Ok, this means new filemap_copy_from_user_iovec() also have to
use regular kmap when page fault has happened.
I'll fix it soon.

> > I updated the writev patch which may be easy to understand.
> > How about it?
> 
> Looks nice.   And yes, you hung onto the atomic kmap across multiple
> iov segments ;)  That will save a tlb invalidate per segment.

Yes.

> > But I have one question, Could let me know if you have any idea,
> > why does filemap_copy_from_user() try to call kamp()+__copy_from_user()
> > again after the first trial get fault.
> > 
> > Is there any meanings?
> 
> We're not allowed to schedule away inside atomic_kmap - must remain
> in the same task, on the same CPU etc.  So the pagefault handler
> will return immediately if we take a pagefault while copying to/from
> userspace while holding an atomic kmap.