Re: [PATCH v7 10/17] mm: uninline the main body of vma_start_write()

Suren Baghdasaryan
2025-01-07T17:45:18Z

On Tue, Jan 7, 2025 at 9:35 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 12/26/24 18:07, Suren Baghdasaryan wrote:
> > vma_start_write() is used in many places and will grow in size very soon.
> > It is not used in performance critical paths and uninlining it should
> > limit the future code size growth.
> > No functional changes.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -6328,6 +6328,20 @@ struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
> > #endif
> >
> > #ifdef CONFIG_PER_VMA_LOCK
> > +void __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq)
> > +{
> > + down_write(&vma->vm_lock.lock);
> > + /*
> > + * We should use WRITE_ONCE() here because we can have concurrent reads
> > + * from the early lockless pessimistic check in vma_start_read().
> > + * We don't really care about the correctness of that early check, but
> > + * we should use WRITE_ONCE() for cleanliness and to keep KCSAN happy.
> > + */
> > + WRITE_ONCE(vma->vm_lock_seq, mm_lock_seq);
> > + up_write(&vma->vm_lock.lock);
> > +}
> > +EXPORT_SYMBOL_GPL(__vma_start_write);
>
> Do any modules need it? If not we shouldn't export.

I'm pretty sure I added it because of the allmodconfig build failure
but let me rerun it and see which module was using it.

>
> > /*
> > * Lookup and lock a VMA under RCU protection. Returned VMA is guaranteed to be
> > * stable and not isolated. If the VMA is not found or is being modified the
>