On Fri, 2008-01-18 at 12:17 +0100, Miklos Szeredi wrote:
> > diff --git a/mm/msync.c b/mm/msync.c
> > index 144a757..a1b3fc6 100644
> > --- a/mm/msync.c
> > +++ b/mm/msync.c
> > @@ -14,6 +14,122 @@
> > #include <linux/syscalls.h>
> > #include <linux/sched.h>
> >
> > +unsigned long masync_pte_range(struct vm_area_struct *vma, pmd_t *pdm,
> > + unsigned long addr, unsigned long end)
> > +{
> > + pte_t *pte;
> > + spinlock_t *ptl;
> > +
> > + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> > + arch_enter_lazy_mmu_mode();
> > + do {
> > + pte_t ptent = *pte;
> > +
> > + if (pte_none(ptent))
> > + continue;
> > +
> > + if (!pte_present(ptent))
> > + continue;
> > +
> > + if (pte_dirty(ptent) && pte_write(ptent)) {
> > + flush_cache_page(vma, addr, pte_pfn(ptent));
>
> Hmm, I'm not sure flush_cache_page() is needed. Or does does dirty
> data in the cache somehow interfere with the page protection?
No, just being paranoid..
> > + ptent = ptep_clear_flush(vma, addr, pte);
> > + ptent = pte_wrprotect(ptent);
> > + set_pte_at(vma->vm_mnm, addr, pte, ptent);
> > + }
> > + } while (pte++, addr += PAGE_SIZE, addr != end);
> > + arch_leave_lazy_mmu_mode();
> > + pte_unmap_unlock(pte - 1, ptl);
> > +
> > + return addr;
> > +}
> > +
> > +unsigned long masync_pmd_range(struct vm_area_struct *vma, pud_t *pud,
> > + unsigned long addr, unsigned long end)
> > +{
> > + pmd_t *pmd;
> > + unsigned long next;
> > +
> > + pmd = pmd_offset(pud, addr);
> > + do {
> > + next = pmd_addr_end(addr, end);
> > + if (pmd_none_or_clear_bad(pmd))
> > + continue;
> > + next = masync_pte_range(vma, pmd, addr, next);
> > + } while (pmd++, addr = next, addr != end);
> > +
> > + return addr;
> > +}
> > +
> > +unsigned long masync_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
> > + unsigned long addr, unsigned long end)
> > +{
> > + pud_t *pud;
> > + unsigned long next;
> > +
> > + pud = pud_offset(pgd, addr);
> > + do {
> > + next = pud_addr_end(addr, end);
> > + if (pud_none_or_clear_bad(pud))
> > + continue;
> > + next = masync_pmd_range(vma, pud, addr, next);
> > + } while (pud++, addr = next, addr != end);
> > +
> > + return addr;
> > +}
> > +
> > +unsigned long masync_pgd_range()
> > +{
> > + pgd_t *pgd;
> > + unsigned long next;
> > +
> > + pgd = pgd_offset(vma->vm_mm, addr);
> > + do {
> > + next = pgd_addr_end(addr, end);
> > + if (pgd_none_of_clear_bad(pgd))
> > + continue;
> > + next = masync_pud_range(vma, pgd, addr, next);
> > + } while (pgd++, addr = next, addr != end);
> > +
> > + return addr;
> > +}
> > +
> > +int masync_vma_one(struct vm_area_struct *vma,
> > + unsigned long start, unsigned long end)
> > +{
> > + if (start < vma->vm_start)
> > + start = vma->vm_start;
> > +
> > + if (end > vma->vm_end)
> > + end = vma->vm_end;
> > +
> > + masync_pgd_range(vma, start, end);
> > +
> > + return 0;
> > +}
> > +
> > +int masync_vma(struct vm_area_struct *vma,
> > + unsigned long start, unsigned long end)
> > +{
> > + struct address_space *mapping;
> > + struct vm_area_struct *vma_iter;
> > +
> > + if (!(vma->vm_flags & VM_SHARED))
> > + return 0;
> > +
> > + mapping = vma->vm_file->f_mapping;
> > +
> > + if (!mapping_cap_account_dirty(mapping))
> > + return 0;
> > +
> > + spin_lock(&mapping->i_mmap_lock);
> > + vma_prio_tree_foreach(vma_iter, &iter, &mapping->i_mmap, start, end)
> > + masync_vma_one(vma_iter, start, end);
> > + spin_unlock(&mapping->i_mmap_lock);
>
> This is hoding i_mmap_lock for possibly quite long. Isn't that going
> to cause problems?
Possibly, I didn't see a quick way to break that iteration.
>From a quick glance at prio_tree.c the iterator isn't valid anymore
after releasing i_mmap_lock. Fixing that would be,.. 'fun'.
I also realized I forgot to copy/paste the prio_tree_iter declaration
and ought to make all these functions static.
But for a quick draft it conveys the idea pretty well, I guess :-)
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