From: David Hildenbrand
Sent: 09 August 2022 21:57
...
These two functions seem to contain a lot of the same tests. They also seem a bit large for 'inline'.
-static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) +/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */ +static inline bool can_follow_write_pte(pte_t pte, struct page *page,
struct vm_area_struct *vma,
unsigned int flags)
{
- return pte_write(pte) ||
((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
- /* If the pte is writable, we can write to the page. */
- if (pte_write(pte))
return true;
- /* Maybe FOLL_FORCE is set to override it? */
- if (!(flags & FOLL_FORCE))
return false;
- /* But FOLL_FORCE has no effect on shared mappings */
- if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
return false;
- /* ... or read-only private ones */
- if (!(vma->vm_flags & VM_MAYWRITE))
return false;
- /* ... or already writable ones that just need to take a write fault */
- if (vma->vm_flags & VM_WRITE)
return false;
- /*
* See can_change_pte_writable(): we broke COW and could map the page
* writable if we have an exclusive anonymous page ...
*/
- if (!page || !PageAnon(page) || !PageAnonExclusive(page))
return false;
- /* ... and a write-fault isn't required for other reasons. */
- if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
return false;
- return !userfaultfd_pte_wp(vma, pte);
}
...
-static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) +/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */ +static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
struct vm_area_struct *vma,
unsigned int flags)
{
- return pmd_write(pmd) ||
((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
- /* If the pmd is writable, we can write to the page. */
- if (pmd_write(pmd))
return true;
- /* Maybe FOLL_FORCE is set to override it? */
- if (!(flags & FOLL_FORCE))
return false;
- /* But FOLL_FORCE has no effect on shared mappings */
- if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
return false;
- /* ... or read-only private ones */
- if (!(vma->vm_flags & VM_MAYWRITE))
return false;
- /* ... or already writable ones that just need to take a write fault */
- if (vma->vm_flags & VM_WRITE)
return false;
- /*
* See can_change_pte_writable(): we broke COW and could map the page
* writable if we have an exclusive anonymous page ...
*/
- if (!page || !PageAnon(page) || !PageAnonExclusive(page))
return false;
- /* ... and a write-fault isn't required for other reasons. */
- if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
return false;
- return !userfaultfd_huge_pmd_wp(vma, pmd);
}
Perhaps only the initial call (common success path?) should be inlined? With the flags and vma tests being moved to an inline helper.
David
- Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)