Re: [PATCH v4 02/14] mm: Switch mm->get_unmapped_area() to a flag

[Edgecombe, Rick P]

On Tue, 2024-03-26 at 23:38 -0700, Dan Williams wrote:
> > +unsigned long
> > +mm_get_unmapped_area(struct mm_struct *mm, struct file *file,
> > +                    unsigned long addr, unsigned long len,
> > +                    unsigned long pgoff, unsigned long flags)
> > +{
> 
> Seems like a small waste to have all call sites now need to push an
> additional @mm argument onto the stack just to figure out what function
> to call.
> 
> > +       if (test_bit(MMF_TOPDOWN, &mm->flags))
> > +               return arch_get_unmapped_area_topdown(file, addr, len, pgoff, flags);
> > +       return arch_get_unmapped_area(file, addr, len, pgoff, flags);
> 
> This seems small enough to be amenable to a static inline, but that
> would require exporting the arch calls which might be painful.
> 
> Would it not be possible to drop the @mm argument and just reference
> current->mm internal to this function? Just call this funcion
> current_get_unmapped_area()?

Hmm, you are right. The callers all pass current->mm. The mm argument could be removed.