Dave wrote:
> On 03/14/2013 10:50 AM, Kirill A. Shutemov wrote:
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -113,11 +113,20 @@ extern void __split_huge_page_pmd(struct vm_area_struct *vma,
> > __split_huge_page_pmd(__vma, __address, \
> > ____pmd); \
> > } while (0)
> > -#define wait_split_huge_page(__anon_vma, __pmd) \
> > +#define wait_split_huge_page(__vma, __pmd) \
> > do { \
> > pmd_t *____pmd = (__pmd); \
> > - anon_vma_lock_write(__anon_vma); \
> > - anon_vma_unlock_write(__anon_vma); \
> > + struct address_space *__mapping = \
> > + vma->vm_file->f_mapping; \
> > + struct anon_vma *__anon_vma = (__vma)->anon_vma; \
> > + if (__mapping) \
> > + mutex_lock(&__mapping->i_mmap_mutex); \
> > + if (__anon_vma) { \
> > + anon_vma_lock_write(__anon_vma); \
> > + anon_vma_unlock_write(__anon_vma); \
> > + } \
> > + if (__mapping) \
> > + mutex_unlock(&__mapping->i_mmap_mutex); \
> > BUG_ON(pmd_trans_splitting(*____pmd) || \
> > pmd_trans_huge(*____pmd)); \
> > } while (0)
>
> That thing was pretty ugly _before_. :) Any chance this can get turned
> in to a function?
Cyclic headers dependencies... :(
> What's the deal with the i_mmap_mutex operation getting split up? I'm
> blanking on what kind of pages would have both anon_vmas and a valid
> mapping.
anon_vma_lock protects all anon pages on vma against splitting.
i_mmap_mutex protects shared pages. None pages can be on both sides, but
MAP_PRIVATE file vma can have both anon and shared pages.
As an option we can lookup for struct page with pmd_page(), check
PageAnon() and serialize only relevant lock, but...
Original macro, in fact, guarantees that *all* pages on the vma is not
splitting, not only the pages pmd is poinging on. PageAnon() check will
change semantics a bit. It shouldn't be a problem, but who knows.
Do you want me to add the check?
--
Kirill A. Shutemov
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