From 097d70c6272f236eb4a29b3fb74b72df3a5344cf Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Thu, 9 Mar 2023 12:12:50 +0100 Subject: [PATCH] mm/mmap/vma_merge: use the proper vma pointer in case 3 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. Link: https://lkml.kernel.org/r/20230309111258.24079-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka Reviewed-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- mm/mmap.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index bbb8d1226281..be8338318cfb 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); } -- 2.34.1