mm/mmap: Reposition vma iterator in mmap_region()

Instead of moving (or leaving) the vma iterator pointing at the previous
vma, leave it pointing at the insert location.  Pointing the vma
iterator at the insert location allows for a cleaner walk of the vma
tree for MAP_FIXED and the no expansion cases.

The vma_prev() call in the case of merging the previous vma is
equivalent to vma_iter_prev_range(), since the vma iterator will be
pointing to the location just before the previous vma.

This change needs to export abort_munmap_vmas() from mm/vma.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

diff --git a/mm/mmap.c b/mm/mmap.c
index 2b7445a002dc0044aa5e8775791ff36546200f18..9285bdf14c4f4d0369be7ab12fb34b994b79df4a 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1400,21 +1400,22 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
                mas_init(&mas_detach, &mt_detach, /* addr = */ 0);
                /* Prepare to unmap any existing mapping in the area */
                if (vms_gather_munmap_vmas(&vms, &mas_detach))
-                       return -ENOMEM;
+                       goto gather_failed;
 
                /* Remove any existing mappings from the vma tree */
                if (vma_iter_clear_gfp(&vmi, addr, end, GFP_KERNEL))
-                       return -ENOMEM;
+                       goto clear_tree_failed;
 
                /* Unmap any existing mapping in the area */
                vms_complete_munmap_vmas(&vms, &mas_detach);
                next = vms.next;
                prev = vms.prev;
-               vma_prev(&vmi);
                vma = NULL;
        } else {
                next = vma_next(&vmi);
                prev = vma_prev(&vmi);
+               if (prev)
+                       vma_iter_next_range(&vmi);
        }
 
        /*
@@ -1427,11 +1428,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
                vm_flags |= VM_ACCOUNT;
        }
 
-       if (vm_flags & VM_SPECIAL) {
-               if (prev)
-                       vma_iter_next_range(&vmi);
+       if (vm_flags & VM_SPECIAL)
                goto cannot_expand;
-       }
 
        /* Attempt to expand an old mapping */
        /* Check next */
@@ -1452,19 +1450,21 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
                merge_start = prev->vm_start;
                vma = prev;
                vm_pgoff = prev->vm_pgoff;
-       } else if (prev) {
-               vma_iter_next_range(&vmi);
+               vma_prev(&vmi); /* Equivalent to going to the previous range */
        }
 
-       /* Actually expand, if possible */
-       if (vma &&
-           !vma_expand(&vmi, vma, merge_start, merge_end, vm_pgoff, next)) {
-               khugepaged_enter_vma(vma, vm_flags);
-               goto expanded;
+       if (vma) {
+               /* Actually expand, if possible */
+               if (!vma_expand(&vmi, vma, merge_start, merge_end, vm_pgoff, next)) {
+                       khugepaged_enter_vma(vma, vm_flags);
+                       goto expanded;
+               }
+
+               /* If the expand fails, then reposition the vma iterator */
+               if (unlikely(vma == prev))
+                       vma_iter_set(&vmi, addr);
        }
 
-       if (vma == prev)
-               vma_iter_set(&vmi, addr);
 cannot_expand:
 
        /*
@@ -1625,6 +1625,12 @@ unacct_error:
                vm_unacct_memory(charged);
        validate_mm(mm);
        return error;
+
+clear_tree_failed:
+       abort_munmap_vmas(&mas_detach);
+gather_failed:
+       validate_mm(mm);
+       return -ENOMEM;
 }
 
 static int __vm_munmap(unsigned long start, size_t len, bool unlock)

diff --git a/mm/vma.c b/mm/vma.c
index 55738b0eb41885fd2200f5ba07f2328a95e5336b..3bfc4934999628f169dbf86c00112e562faa2703 100644 (file)
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -646,22 +646,6 @@ again:
                uprobe_mmap(vp->insert);
 }
 
-/*
- * abort_munmap_vmas - Undo any munmap work and free resources
- *
- * Reattach any detached vmas and free up the maple tree used to track the vmas.
- */
-static inline void abort_munmap_vmas(struct ma_state *mas_detach)
-{
-       struct vm_area_struct *vma;
-
-       mas_set(mas_detach, 0);
-       mas_for_each(mas_detach, vma, ULONG_MAX)
-               vma_mark_detached(vma, false);
-
-       __mt_destroy(mas_detach->tree);
-}
-
 /*
  * vms_complete_munmap_vmas() - Finish the munmap() operation
  * @vms: The vma munmap struct

diff --git a/mm/vma.h b/mm/vma.h
index 0e214bbf443e6db47b5765c0af91e9dde85e37be..c85fc7c888a8e066df7cff537add43a93ce95561 100644 (file)
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -116,6 +116,22 @@ int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
 void vms_complete_munmap_vmas(struct vma_munmap_struct *vms,
                struct ma_state *mas_detach);
 
+/*
+ * abort_munmap_vmas - Undo any munmap work and free resources
+ *
+ * Reattach any detached vmas and free up the maple tree used to track the vmas.
+ */
+static inline void abort_munmap_vmas(struct ma_state *mas_detach)
+{
+       struct vm_area_struct *vma;
+
+       mas_set(mas_detach, 0);
+       mas_for_each(mas_detach, vma, ULONG_MAX)
+               vma_mark_detached(vma, false);
+
+       __mt_destroy(mas_detach->tree);
+}
+
 int
 do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
                    struct mm_struct *mm, unsigned long start,