Refactor vma_merge() to make it shorter, more understandable and
suitable for tracing of successful merges made possible by following
patches in the series.
Signed-off-by: Jakub Matěna <matenajakub@xxxxxxxxx>
---
mm/mmap.c | 81 +++++++++++++++++++++++++++----------------------------
1 file changed, 39 insertions(+), 42 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 1e8fdb0b51ed..b55e11f20571 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1172,6 +1172,9 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
struct vm_area_struct *area, *next;
int err;
+ int merge_prev = 0;
+ int merge_both = 0;
+ int merge_next = 0;
/*
* We later require that vma->vm_flags == vm_flags,
@@ -1191,65 +1194,59 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
VM_WARN_ON(addr >= end);
/*
- * Can it merge with the predecessor?
+ * Can we merge predecessor?
*/
if (prev && prev->vm_end == addr &&
mpol_equal(vma_policy(prev), policy) &&
can_vma_merge_after(prev, vm_flags,
anon_vma, file, pgoff,
vm_userfaultfd_ctx, anon_name)) {
- /*
- * OK, it can. Can we now merge in the successor as well?
- */
- if (next && end == next->vm_start &&
- mpol_equal(policy, vma_policy(next)) &&
- can_vma_merge_before(next, vm_flags,
- anon_vma, file,
- pgoff+pglen,
- vm_userfaultfd_ctx, anon_name) &&
- is_mergeable_anon_vma(prev->anon_vma,
- next->anon_vma, NULL)) {
- /* cases 1, 6 */
- err = __vma_adjust(prev, prev->vm_start,
- next->vm_end, prev->vm_pgoff, NULL,
- prev);
- } else /* cases 2, 5, 7 */
- err = __vma_adjust(prev, prev->vm_start,
- end, prev->vm_pgoff, NULL, prev);
- if (err)
- return NULL;
- khugepaged_enter_vma_merge(prev, vm_flags);
- return prev;
+ merge_prev = true;
}
-
/*
- * Can this new request be merged in front of next?
+ * Can we merge successor?
*/
if (next && end == next->vm_start &&
mpol_equal(policy, vma_policy(next)) &&
can_vma_merge_before(next, vm_flags,
- anon_vma, file, pgoff+pglen,
- vm_userfaultfd_ctx, anon_name)) {
+ anon_vma, file, pgoff+pglen,
+ vm_userfaultfd_ctx, anon_name)) {
+ merge_next = true;
+ }
+ /*
+ * Can we merge both predecessor and successor?
+ */
+ if (merge_prev && merge_next)
+ merge_both = is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL);
+
+ if (merge_both) { /* cases 1, 6 */
+ err = __vma_adjust(prev, prev->vm_start,
+ next->vm_end, prev->vm_pgoff, NULL,
+ prev);
+ area = prev;
+ } else if (merge_prev) { /* cases 2, 5, 7 */
+ err = __vma_adjust(prev, prev->vm_start,
+ end, prev->vm_pgoff, NULL, prev);
+ area = prev;
+ } else if (merge_next) {
if (prev && addr < prev->vm_end) /* case 4 */
err = __vma_adjust(prev, prev->vm_start,
- addr, prev->vm_pgoff, NULL, next);
- else { /* cases 3, 8 */
+ addr, prev->vm_pgoff, NULL, next);
+ else /* cases 3, 8 */
err = __vma_adjust(area, addr, next->vm_end,
- next->vm_pgoff - pglen, NULL, next);
- /*
- * In case 3 area is already equal to next and
- * this is a noop, but in case 8 "area" has
- * been removed and next was expanded over it.
- */
- area = next;
- }
- if (err)
- return NULL;
- khugepaged_enter_vma_merge(area, vm_flags);
- return area;
+ next->vm_pgoff - pglen, NULL, next);
+ area = next;
+ } else {
+ err = -1;
}
- return NULL;
+ /*
+ * Cannot merge with predecessor or successor or error in __vma_adjust?
+ */
+ if (err)
+ return NULL;
+ khugepaged_enter_vma_merge(area, vm_flags);
+ return area;
}
/*
--
2.34.1
