In case 3 we we use 'next' for everything but vma_pgoff. So use 'next'
for that as well, instead of 'mid', for consistency. Then in case 8 we
have to use 'mid' explicitly, which should also make the intent more
obvious.
Adjust the diagram for cases 1-3 in the comment to match the code - we
are using 'next' for case 3 so mark the range with XXXX instead of NNNN.
For case 2 that's a no-op as the code doesn't touch 'next' or 'mid'. For
case 1 it's now wrong but that will be fixed next.
No functional change.
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
mm/mmap.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 0a8b052e3022..1af4c9bc2c87 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -857,11 +857,11 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
* mmap, brk or case 4 below case 5 below
* mremap move:
* AAAA AAAA
- * PPPP NNNN PPPPNNNNXXXX
+ * PPPP XXXX PPPPNNNNXXXX
* might become might become
* PPPPPPPPPPPP 1 or PPPPPPPPPPPP 6 or
- * PPPPPPPPNNNN 2 or PPPPPPPPXXXX 7 or
- * PPPPNNNNNNNN 3 PPPPXXXXXXXX 8
+ * PPPPPPPPXXXX 2 or PPPPPPPPXXXX 7 or
+ * PPPPXXXXXXXX 3 PPPPXXXXXXXX 8
*
* It is important for case 8 that the vma NNNN overlapping the
* region AAAA is never going to extended over XXXX. Instead XXXX must
@@ -978,9 +978,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
vma = next; /* case 3 */
vma_start = addr;
vma_end = next->vm_end;
- vma_pgoff = mid->vm_pgoff;
+ vma_pgoff = next->vm_pgoff;
err = 0;
if (mid != next) { /* case 8 */
+ vma_pgoff = mid->vm_pgoff;
remove = mid;
err = dup_anon_vma(next, mid);
}
--
2.39.2
