linux-kernel - [PATCH] mm/mmap.c: make vma_merge() comment more easy to understand

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Message-Id: <20191030012445.16944-1-richardw.yang@linux.intel.com>
Date:   Wed, 30 Oct 2019 09:24:45 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     akpm@...ux-foundation.org, richardw.yang@...ux.intel.com,
        rppt@...ux.ibm.com, will@...nel.org, mhocko@...e.com,
        catalin.marinas@....com, aarcange@...hat.com, jannh@...gle.com,
        darrick.wong@...cle.com, steve.capper@....com, walken@...gle.com,
        dave.hansen@...ux.intel.com, tiny.windzz@...il.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mm/mmap.c: make vma_merge() comment more easy to understand

Case 1/6, 2/7 and 3/8 have the same pattern and we handle them in the
same logic.

Rearrange the comment to make it a little easy for audience to
understand.

Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
---
 mm/mmap.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index a7d8c84d19b7..d485100f9d29 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1116,15 +1116,18 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
  * the area passed down from mprotect_fixup, never extending beyond one
  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
  *
- *     AAAA             AAAA                AAAA          AAAA
- *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
- *    cannot merge    might become    might become    might become
- *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
- *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
- *    mremap move:                                    PPPPXXXXXXXX 8
- *        AAAA
- *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
- *    might become    case 1 below    case 2 below    case 3 below
+ *     AAAA             AAAA                   AAAA
+ *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
+ *    cannot merge    might become       might become
+ *                    PPNNNNNNNNNN       PPPPPPPPPPNN
+ *    mmap, brk or    case 4 below       case 5 below
+ *    mremap move:
+ *                        AAAA               AAAA
+ *                    PPPP    NNNN       PPPPNNNNXXXX
+ *                    might become       might become
+ *                    PPPPPPPPPPPP 1 or  PPPPPPPPPPPP 6 or
+ *                    PPPPPPPPNNNN 2 or  PPPPPPPPXXXX 7 or
+ *                    PPPPNNNNNNNN 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
-- 
2.17.1