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Message-ID: <10798a7d-e157-03c2-abf4-f005a3507cae@suse.cz>
Date: Thu, 20 Jan 2022 12:58:47 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Liam Howlett <liam.howlett@...cle.com>,
"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>
Cc: 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
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?
>
> 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(...)"
>
> 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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