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Date: Wed, 26 Jan 2022 02:48:26 +0000
From: Liam Howlett <liam.howlett@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
CC: "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Song Liu <songliubraving@...com>,
Davidlohr Bueso <dave@...olabs.net>,
"Paul E . McKenney" <paulmck@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Laurent Dufour <ldufour@...ux.ibm.com>,
David Rientjes <rientjes@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Rik van Riel <riel@...riel.com>,
Peter Zijlstra <peterz@...radead.org>,
Michel Lespinasse <walken.cr@...il.com>,
Jerome Glisse <jglisse@...hat.com>,
Minchan Kim <minchan@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 55/66] mm/mempolicy: Use maple tree iterators instead
of vma linked list
* Vlastimil Babka <vbabka@...e.cz> [220120 06:58]:
> On 12/1/21 15:30, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> >
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> > mm/mempolicy.c | 53 ++++++++++++++++++++++++++------------------------
> > 1 file changed, 28 insertions(+), 25 deletions(-)
> >
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 10e9c87260ed..0e2d918f4f30 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -377,9 +377,10 @@ void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new)
> > void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
> > {
> > struct vm_area_struct *vma;
> > + MA_STATE(mas, &mm->mm_mt, 0, 0);
>
> VMA_ITERATOR?
Yes, I will make this change. Thanks.
>
> >
> > mmap_write_lock(mm);
> > - for (vma = mm->mmap; vma; vma = vma->vm_next)
> > + mas_for_each(&mas, vma, ULONG_MAX)
> > mpol_rebind_policy(vma->vm_policy, new);
> > mmap_write_unlock(mm);
> > }
> > @@ -652,7 +653,7 @@ static unsigned long change_prot_numa(struct vm_area_struct *vma,
> > static int queue_pages_test_walk(unsigned long start, unsigned long end,
> > struct mm_walk *walk)
> > {
> > - struct vm_area_struct *vma = walk->vma;
> > + struct vm_area_struct *next, *vma = walk->vma;
> > struct queue_pages *qp = walk->private;
> > unsigned long endvma = vma->vm_end;
> > unsigned long flags = qp->flags;
> > @@ -667,9 +668,10 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
> > /* hole at head side of range */
> > return -EFAULT;
> > }
> > + next = find_vma(vma->vm_mm, vma->vm_end);
> > if (!(flags & MPOL_MF_DISCONTIG_OK) &&
> > ((vma->vm_end < qp->end) &&
> > - (!vma->vm_next || vma->vm_end < vma->vm_next->vm_start)))
> > + (!next || vma->vm_end < next->vm_start)))
> > /* hole at middle or tail of range */
> > return -EFAULT;
> >
> > @@ -783,28 +785,24 @@ static int vma_replace_policy(struct vm_area_struct *vma,
> > static int mbind_range(struct mm_struct *mm, unsigned long start,
> > unsigned long end, struct mempolicy *new_pol)
> > {
> > - struct vm_area_struct *next;
> > + MA_STATE(mas, &mm->mm_mt, start - 1, start - 1);
> > struct vm_area_struct *prev;
> > struct vm_area_struct *vma;
> > int err = 0;
> > pgoff_t pgoff;
> > - unsigned long vmstart;
> > - unsigned long vmend;
> > -
> > - vma = find_vma(mm, start);
> > - VM_BUG_ON(!vma);
> >
> > - prev = vma->vm_prev;
> > - if (start > vma->vm_start)
> > - prev = vma;
> > + prev = mas_find_rev(&mas, 0);
> > + if (prev && (start < prev->vm_end))
> > + vma = prev;
> > + else
> > + vma = mas_next(&mas, end - 1);
> >
> > - for (; vma && vma->vm_start < end; prev = vma, vma = next) {
> > - next = vma->vm_next;
> > - vmstart = max(start, vma->vm_start);
> > - vmend = min(end, vma->vm_end);
> > + do {
> > + unsigned long vmstart = max(start, vma->vm_start);
> > + unsigned long vmend = min(end, vma->vm_end);
>
> What if vma is null? Shouldn't this rather be a "for (; vma; vma =
> mas_next(...)"
We have already found the vma above. I am re-using the maple state to
save walking the tree. I will re-add the VM_BUG_ON(!vma), but I think
it's more efficient the way it is.
>
> >
> > if (mpol_equal(vma_policy(vma), new_pol))
> > - continue;
> > + goto next;
> >
> > pgoff = vma->vm_pgoff +
> > ((vmstart - vma->vm_start) >> PAGE_SHIFT);
> > @@ -812,8 +810,8 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
> > vma->anon_vma, vma->vm_file, pgoff,
> > new_pol, vma->vm_userfaultfd_ctx);
> > if (prev) {
> > + mas_pause(&mas);
> > vma = prev;
> > - next = vma->vm_next;
> > if (mpol_equal(vma_policy(vma), new_pol))
> > continue;
> > /* vma_merge() joined vma && vma->next, case 8 */
> > @@ -823,19 +821,23 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
> > err = split_vma(vma->vm_mm, vma, vmstart, 1);
> > if (err)
> > goto out;
> > + mas_pause(&mas);
> > }
> > if (vma->vm_end != vmend) {
> > err = split_vma(vma->vm_mm, vma, vmend, 0);
> > if (err)
> > goto out;
> > + /* mas_pause() unnecessary as the loop is ending */
> > }
> > - replace:
> > +replace:
> > err = vma_replace_policy(vma, new_pol);
> > if (err)
> > goto out;
> > - }
> > +next:
> > + prev = vma;
> > + } while ((vma = mas_next(&mas, end - 1)) != NULL);
> >
> > - out:
> > +out:
> > return err;
> > }
> >
> > @@ -1053,6 +1055,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > int flags)
> > {
> > nodemask_t nmask;
> > + struct vm_area_struct *vma;
> > LIST_HEAD(pagelist);
> > int err = 0;
> > struct migration_target_control mtc = {
> > @@ -1068,8 +1071,9 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > * need migration. Between passing in the full user address
> > * space range and MPOL_MF_DISCONTIG_OK, this call can not fail.
> > */
> > + vma = find_vma(mm, 0);
> > VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));
> > - queue_pages_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> > + queue_pages_range(mm, vma->vm_start, mm->task_size, &nmask,
> > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> >
> > if (!list_empty(&pagelist)) {
> > @@ -1198,13 +1202,12 @@ static struct page *new_page(struct page *page, unsigned long start)
> > {
> > struct vm_area_struct *vma;
> > unsigned long address;
> > + MA_STATE(mas, ¤t->mm->mm_mt, start, start);
> >
> > - vma = find_vma(current->mm, start);
> > - while (vma) {
> > + mas_for_each(&mas, vma, ULONG_MAX) {
> > address = page_address_in_vma(page, vma);
> > if (address != -EFAULT)
> > break;
> > - vma = vma->vm_next;
> > }
> >
> > if (PageHuge(page)) {
>
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