diff options
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index e2e2c970374a..343859b1190d 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -898,7 +898,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, { pgoff_t pglen = (end - addr) >> PAGE_SHIFT; pgoff_t vma_pgoff; - struct vm_area_struct *curr, *next, *res = NULL; + struct vm_area_struct *curr, *next, *res; struct vm_area_struct *vma, *adjust, *remove, *remove2; int err = -1; bool merge_prev = false; @@ -926,14 +926,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, else next = NULL; /* case 5 */ - /* verify some invariant that must be enforced by the caller */ + /* + * By default, we return prev. Cases 3, 4, 8 will instead return next + * and cases 3, 8 will also update vma to point at next. + */ + res = vma = prev; + + /* Verify some invariant that must be enforced by the caller. */ VM_WARN_ON(prev && addr <= prev->vm_start); - VM_WARN_ON(curr && end > curr->vm_end); + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); VM_WARN_ON(addr >= end); if (prev) { - res = prev; - vma = prev; vma_start = prev->vm_start; vma_pgoff = prev->vm_pgoff; /* Can we merge the predecessor? */ @@ -944,6 +948,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma_prev(vmi); } } + /* Can we merge the successor? */ if (next && mpol_equal(policy, vma_policy(next)) && can_vma_merge_before(next, vm_flags, @@ -984,6 +989,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, adj_start = -(prev->vm_end - addr); err = dup_anon_vma(next, prev); } else { + /* + * Note that cases 3 and 8 are the ONLY ones where prev + * is permitted to be (but is not necessarily) NULL. + */ vma = next; /* case 3 */ vma_start = addr; vma_end = next->vm_end; |