Messages in this thread |  | | Date | Sat, 31 May 2003 16:48:16 -0700 | From | "Paul E. McKenney" <> | Subject | Re: Always passing mm and vma down (was: [RFC][PATCH] Convert do_no_page() to a hook to avoid DFS race) |
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On Sat, May 31, 2003 at 10:46:18AM +0200, Ingo Oeser wrote: > On Fri, May 30, 2003 at 04:41:50PM -0700, Paul E. McKenney wrote: > > -struct page * > > -ia32_install_shared_page (struct vm_area_struct *vma, unsigned long address, int no_share) > > +int > > +ia32_install_shared_page (struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access, pmd_t *pmd) > > Why do we always pass mm and vma down, even if vma->vm_mm > contains the mm, where the vma belongs to? Is the connection > between a vma and its mm also protected by the mmap_sem? > > Is this really necessary or an oversight and we waste a lot of > stack in a lot of places? > > If we just need it for accounting: We need current->mm, if we > need it to locate the next vma relatively to this vma, vma->vm_mm > is the one.
Interesting point. The original do_no_page() API does this as well:
static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access, pte_t *page_table, pmd_t *pmd)
As does do_anonymous_page(). I assumed that there were corner cases where this one-to-one correspondence did not exist, but must confess that I did not go looking for them.
Or is this a performance issue, avoiding a dereference and possible cache miss?
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