[PATCH v7 66/70] nommu: Remove uses of VMA linked list

Liam Howlett
2022-04-04T14:43:56Z

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

Use the maple tree or VMA iterator instead. This is faster and will
allow us to shrink the VMA.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/nommu.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 26a9056e508f..645d11d3a8ab 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1381,6 +1381,7 @@ static int shrink_vma(struct mm_struct *mm,
*/
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
{
+ MA_STATE(mas, &mm->mm_mt, start, start);
struct vm_area_struct *vma;
unsigned long end;
int ret;
@@ -1392,7 +1393,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list
end = start + len;

/* find the first potentially overlapping VMA */
- vma = find_vma(mm, start);
+ vma = mas_find(&mas, end - 1);
if (!vma) {
static int limit;
if (limit < 5) {
@@ -1411,7 +1412,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list
return -EINVAL;
if (end == vma->vm_end)
goto erase_whole_vma;
- vma = vma->vm_next;
+ vma = mas_next(&mas, end - 1);
} while (vma);
return -EINVAL;
} else {
@@ -1460,6 +1461,7 @@ SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
*/
void exit_mmap(struct mm_struct *mm)
{
+ VMA_ITERATOR(vmi, mm, 0);
struct vm_area_struct *vma;

if (!mm)
@@ -1467,12 +1469,17 @@ void exit_mmap(struct mm_struct *mm)

mm->total_vm = 0;

- while ((vma = mm->mmap)) {
- mm->mmap = vma->vm_next;
+ /*
+ * Lock the mm to avoid assert complaining even though this is the only
+ * user of the mm
+ */
+ mmap_write_lock(mm);
+ for_each_vma(vmi, vma) {
delete_vma_from_mm(vma);
delete_vma(mm, vma);
cond_resched();
}
+ mmap_write_unlock(mm);
__mt_destroy(&mm->mm_mt);
}

--
2.34.1