Re: [PATCHv2, RFC 17/30] thp: wait_split_huge_page(): serialize overi_mmap_mutex too

From: Dave
Date: Fri Mar 22 2013 - 14:13:48 EST


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?

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.
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