Re: [PATCH 3/5] mm: Rename __thp_get_unmapped_area to mm_get_unmapped_area_aligned

[Peter Xu]

On Fri, Jun 13, 2025 at 11:17:45AM -0300, Jason Gunthorpe wrote:
> On Fri, Jun 13, 2025 at 09:41:09AM -0400, Peter Xu wrote:
> > @@ -1088,7 +1088,7 @@ static inline bool is_transparent_hugepage(const struct folio *folio)
> >  		folio_test_large_rmappable(folio);
> >  }
> >  
> > -static unsigned long __thp_get_unmapped_area(struct file *filp,
> > +unsigned long mm_get_unmapped_area_aligned(struct file *filp,
> >  		unsigned long addr, unsigned long len,
> >  		loff_t off, unsigned long flags, unsigned long size,
> >  		vm_flags_t vm_flags)
> 
> Please add a kdoc for this since it is going to be exported..

Will do.  And thanks for the super fast feedbacks. :)

> 
> I didn't intuitively guess how it works or why there are two
> length/size arguments. It seems to have an exciting return code as
> well.
> 
> I suppose size is the alignment target? Maybe rename the parameter too?

Yes, when the kdoc is there it'll be more obvious.  So far "size" is ok to
me, but if you have better suggestion please shoot - whatever I came up
with so far seems to be too long, and maybe not necessary when kdoc will be
available too.

> 
> For the purposes of VFIO do we need to be careful about math overflow here:
> 
> 	loff_t off_end = off + len;
> 	loff_t off_align = round_up(off, size);
> 
> ?

IIUC the 1st one was covered by the latter check here:

        (off + len_pad) < off

Indeed I didn't see what makes sure the 2nd won't overflow.

How about I add it within this patch?  A whole fixup could look like this: