On Wed 01-06-22 14:47:41, Suren Baghdasaryan wrote:
> On Wed, Jun 1, 2022 at 2:36 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
[...]
> > But iirc mapletree wants to retain a write_lock here, so I ended up with
> >
> > void exit_mmap(struct mm_struct *mm)
> > {
> > struct mmu_gather tlb;
> > struct vm_area_struct *vma;
> > unsigned long nr_accounted = 0;
> > MA_STATE(mas, &mm->mm_mt, 0, 0);
> > int count = 0;
> >
> > /* mm's last user has gone, and its about to be pulled down */
> > mmu_notifier_release(mm);
> >
> > mmap_write_lock(mm);
> > arch_exit_mmap(mm);
> >
> > vma = mas_find(&mas, ULONG_MAX);
> > if (!vma) {
> > /* Can happen if dup_mmap() received an OOM */
> > mmap_write_unlock(mm);
> > return;
> > }
> >
> > lru_add_drain();
> > flush_cache_mm(mm);
> > tlb_gather_mmu_fullmm(&tlb, mm);
> > /* update_hiwater_rss(mm) here? but nobody should be looking */
> > /* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
> > unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX);
> >
> > /*
> > * Set MMF_OOM_SKIP to hide this task from the oom killer/reaper
> > * because the memory has been already freed. Do not bother checking
> > * mm_is_oom_victim because setting a bit unconditionally is cheaper.
> > */
> > set_bit(MMF_OOM_SKIP, &mm->flags);
> > free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
> > USER_PGTABLES_CEILING);
> > tlb_finish_mmu(&tlb);
> >
> > /*
> > * Walk the list again, actually closing and freeing it, with preemption
> > * enabled, without holding any MM locks besides the unreachable
> > * mmap_write_lock.
> > */
> > do {
> > if (vma->vm_flags & VM_ACCOUNT)
> > nr_accounted += vma_pages(vma);
> > remove_vma(vma);
> > count++;
> > cond_resched();
> > } while ((vma = mas_find(&mas, ULONG_MAX)) != NULL);
> >
> > BUG_ON(count != mm->map_count);
> >
> > trace_exit_mmap(mm);
> > __mt_destroy(&mm->mm_mt);
> > mm->mmap = NULL;
>
> ^^^ this line above needs to be removed when the patch is applied over
> the maple tree patchset.
I am not fully up to date on the maple tree changes. Could you explain
why resetting mm->mmap is not needed anymore please?
--
Michal Hocko
SUSE Labs
