[PATCH v13 57/70] mm/mlock: use vma iterator and maple state instead of vma linked list

Liam Howlett
2022-08-22T15:13:12Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Handle overflow checking in count_mm_mlocked_page_nr() differently.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
mm/mlock.c | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index b14e929084cc..43d19a1f28eb 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -471,6 +471,7 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
unsigned long nstart, end, tmp;
struct vm_area_struct *vma, *prev;
int error;
+ MA_STATE(mas, &current->mm->mm_mt, start, start);

VM_BUG_ON(offset_in_page(start));
VM_BUG_ON(len != PAGE_ALIGN(len));
@@ -479,13 +480,14 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
return -EINVAL;
if (end == start)
return 0;
- vma = find_vma(current->mm, start);
- if (!vma || vma->vm_start > start)
+ vma = mas_walk(&mas);
+ if (!vma)
return -ENOMEM;

- prev = vma->vm_prev;
if (start > vma->vm_start)
prev = vma;
+ else
+ prev = mas_prev(&mas, 0);

for (nstart = start ; ; ) {
vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
@@ -505,7 +507,7 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
if (nstart >= end)
break;

- vma = prev->vm_next;
+ vma = find_vma(prev->vm_mm, prev->vm_end);
if (!vma || vma->vm_start != nstart) {
error = -ENOMEM;
break;
@@ -526,24 +528,23 @@ static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
{
struct vm_area_struct *vma;
unsigned long count = 0;
+ unsigned long end;
+ VMA_ITERATOR(vmi, mm, start);

if (mm == NULL)
mm = current->mm;

- vma = find_vma(mm, start);
- if (vma == NULL)
- return 0;
-
- for (; vma ; vma = vma->vm_next) {
- if (start >= vma->vm_end)
- continue;
- if (start + len <= vma->vm_start)
- break;
+ /* Don't overflow past ULONG_MAX */
+ if (unlikely(ULONG_MAX - len < start))
+ end = ULONG_MAX;
+ else
+ end = start + len;
+ for_each_vma_range(vmi, vma, end) {
if (vma->vm_flags & VM_LOCKED) {
if (start > vma->vm_start)
count -= (start - vma->vm_start);
- if (start + len < vma->vm_end) {
- count += start + len - vma->vm_start;
+ if (end < vma->vm_end) {
+ count += end - vma->vm_start;
break;
}
count += vma->vm_end - vma->vm_start;
@@ -659,6 +660,7 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
*/
static int apply_mlockall_flags(int flags)
{
+ MA_STATE(mas, &current->mm->mm_mt, 0, 0);
struct vm_area_struct *vma, *prev = NULL;
vm_flags_t to_add = 0;

@@ -679,7 +681,7 @@ static int apply_mlockall_flags(int flags)
to_add |= VM_LOCKONFAULT;
}

- for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
+ mas_for_each(&mas, vma, ULONG_MAX) {
vm_flags_t newflags;

newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
@@ -687,6 +689,7 @@ static int apply_mlockall_flags(int flags)

/* Ignore errors */
mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
+ mas_pause(&mas);
cond_resched();
}
out:
--
2.35.1