[PATCH v12 56/69] mm/mempolicy: use vma iterator & maple state instead of vma linked list

Liam Howlett
2022-07-20T02:23:27Z

Reworked the way mbind_range() finds the first VMA to reuse the maple
state and limit the number of tree walks needed.

Note, this drops the VM_BUG_ON(!vma) call, which would catch a start
address higher than the last VMA. The code was written in a way that
allowed no VMA updates to occur and still return success. There should be
no functional change to this scenario with the new code.

Link: https://lkml.kernel.org/r/20220504011345.662299-41-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220621204632.3370049-57-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/mempolicy.c | 56 ++++++++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d39b01fd52fe..d5993b47bdb8 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -381,9 +381,10 @@ 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;
+ VMA_ITERATOR(vmi, mm, 0);

mmap_write_lock(mm);
- for (vma = mm->mmap; vma; vma = vma->vm_next)
+ for_each_vma(vmi, vma)
mpol_rebind_policy(vma->vm_policy, new);
mmap_write_unlock(mm);
}
@@ -656,7 +657,7 @@ 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;
@@ -671,9 +672,10 @@ 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;

@@ -787,26 +789,24 @@ 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)
{
+ 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 = vma->vm_next) {
- vmstart = max(start, vma->vm_start);
- vmend = min(end, vma->vm_end);
+ for (; vma; vma = mas_next(&mas, end - 1)) {
+ unsigned long vmstart = max(start, vma->vm_start);
+ unsigned long vmend = min(end, vma->vm_end);

if (mpol_equal(vma_policy(vma), new_pol))
- continue;
+ goto next;

pgoff = vma->vm_pgoff +
((vmstart - vma->vm_start) >> PAGE_SHIFT);
@@ -815,6 +815,8 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
new_pol, vma->vm_userfaultfd_ctx,
anon_vma_name(vma));
if (prev) {
+ /* vma_merge() invalidated the mas */
+ mas_pause(&mas);
vma = prev;
goto replace;
}
@@ -822,19 +824,25 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
err = split_vma(vma->vm_mm, vma, vmstart, 1);
if (err)
goto out;
+ /* split_vma() invalidated the mas */
+ mas_pause(&mas);
}
if (vma->vm_end != vmend) {
err = split_vma(vma->vm_mm, vma, vmend, 0);
if (err)
goto out;
+ /* split_vma() invalidated the mas */
+ mas_pause(&mas);
}
- replace:
+replace:
err = vma_replace_policy(vma, new_pol);
if (err)
goto out;
+next:
+ prev = vma;
}

- out:
+out:
return err;
}

@@ -1049,6 +1057,7 @@ 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 = {
@@ -1064,8 +1073,9 @@ 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)) {
@@ -1195,14 +1205,13 @@ static struct page *new_page(struct page *page, unsigned long start)
struct folio *dst, *src = page_folio(page);
struct vm_area_struct *vma;
unsigned long address;
+ VMA_ITERATOR(vmi, current->mm, start);
gfp_t gfp = GFP_HIGHUSER_MOVABLE | __GFP_RETRY_MAYFAIL;

- vma = find_vma(current->mm, start);
- while (vma) {
+ for_each_vma(vmi, vma) {
address = page_address_in_vma(page, vma);
if (address != -EFAULT)
break;
- vma = vma->vm_next;
}

if (folio_test_hugetlb(src))
@@ -1480,6 +1489,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
unsigned long vmend;
unsigned long end;
int err = -ENOENT;
+ VMA_ITERATOR(vmi, mm, start);

start = untagged_addr(start);
if (start & ~PAGE_MASK)
@@ -1505,9 +1515,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
if (end == start)
return 0;
mmap_write_lock(mm);
- vma = find_vma(mm, start);
- for (; vma && vma->vm_start < end; vma = vma->vm_next) {
-
+ for_each_vma_range(vmi, vma, end) {
vmstart = max(start, vma->vm_start);
vmend = min(end, vma->vm_end);
new = mpol_dup(vma_policy(vma));
--
2.35.1