mm/mmap: Optimize mmap_region() use of maple states

Only walk down once after the tree was modified with the munmap call.  Copy mas
to find prev and next.  Only reset mas if the address changed.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>

diff --git a/mm/mmap.c b/mm/mmap.c
index 73fc95a10c8d3cb91ab1490dd635a617f58ec631..64a2addb47e2e48b31b1524a13671410ac3fa2ea 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2541,11 +2541,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
        }
 
        mas_set_range(&mas, addr, end - 1);
-       if (vm_flags & VM_SPECIAL) {
-               ma_prev = mas;
-               prev = mas_prev(&ma_prev, 0);
+       mas_walk(&mas);  // Walk to the empty area (munmapped above)
+       ma_prev = mas;
+       prev = mas_prev(&ma_prev, 0);
+
+       if (vm_flags & VM_SPECIAL)
                goto cannot_expand;
-       }
 
        /* Attempt to expand an old mapping */
 
@@ -2561,26 +2562,23 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
                        merge_end = next->vm_end;
                        vma = next;
                        vm_pgoff = next->vm_pgoff - pglen;
-                       tmp = mas;
                }
        }
 
        /* Check prev */
-       ma_prev = tmp;
-       prev = mas_prev(&ma_prev, 0);
        if (prev && prev->vm_end == addr && !vma_policy(prev) &&
            can_vma_merge_after(prev, vm_flags, NULL, file, pgoff,
                                NULL_VM_UFFD_CTX)) {
                /* Try to expand the prev over the requested area */
                merge_start = prev->vm_start;
                vma = prev;
-               tmp = ma_prev;
+               mas = ma_prev;
                vm_pgoff = prev->vm_pgoff;
        }
 
        /* Actually expand, if possible */
        if (vma &&
-           !vma_expand(&tmp, vma, merge_start, merge_end, vm_pgoff, next)) {
+           !vma_expand(&mas, vma, merge_start, merge_end, vm_pgoff, next)) {
                khugepaged_enter_vma_merge(vma, vm_flags);
                goto expanded;
        }
@@ -2631,8 +2629,11 @@ cannot_expand:
                 *         f_op->mmap method. -DaveM
                 */
                WARN_ON_ONCE(addr != vma->vm_start);
+               if (addr != vma->vm_start) {
+                       addr = vma->vm_start;
+                       mas_set_range(&mas, addr, end - 1);
+               }
 
-               addr = vma->vm_start;
 
                /* If vm_flags changed after call_mmap(), we should try merge vma again
                 * as we may succeed this time.
@@ -2680,8 +2681,6 @@ cannot_expand:
                        goto free_vma;
        }
 
-       // addr may have changed.
-       mas_set_range(&mas, addr, end - 1);
        vma_mas_link(mm, vma, &mas);
 
        /* Once vma denies write, undo our temporary denial count */