On Wed 13-06-12 16:59:23, Michal Hocko wrote:
> On Wed 13-06-12 15:57:23, Aneesh Kumar K.V wrote:
> > From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> >
> > Use a mmu_gather instead of a temporary linked list for accumulating
> > pages when we unmap a hugepage range
>
> Sorry for coming up with the comment that late but you owe us an
> explanation _why_ you are doing this.
>
> I assume that this fixes a real problem when we take i_mmap_mutex
> already up in
> unmap_mapping_range
> mutex_lock(&mapping->i_mmap_mutex);
> unmap_mapping_range_tree | unmap_mapping_range_list
> unmap_mapping_range_vma
> zap_page_range_single
> unmap_single_vma
> unmap_hugepage_range
> mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
>
> And that this should have been marked for stable as well (I haven't
> checked when this has been introduced).
>
> But then I do not see how this help when you still do this:
> [...]
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 1b7dc66..545e18a 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -1326,8 +1326,11 @@ static void unmap_single_vma(struct mmu_gather *tlb,
> > * Since no pte has actually been setup, it is
> > * safe to do nothing in this case.
> > */
> > - if (vma->vm_file)
> > - unmap_hugepage_range(vma, start, end, NULL);
> > + if (vma->vm_file) {
> > + mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
> > + __unmap_hugepage_range(tlb, vma, start, end, NULL);
> > + mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
> > + }
> > } else
> > unmap_page_range(tlb, vma, start, end, details);
> > }
Ahhh, you are removing the lock in the next patch. Really confusing and
not nice for the stable backport.
Could you merge those two patches and add Cc: stable?
Then you can add my
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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