linux-kernel - [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon

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Date:   Mon, 18 Nov 2019 20:24:04 +0800
From:   linmiaohe <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <richardw.yang@...ux.intel.com>,
        <sfr@...b.auug.org.au>, <rppt@...ux.ibm.com>, <jannh@...gle.com>,
        <steve.capper@....com>, <catalin.marinas@....com>,
        <aarcange@...hat.com>, <walken@...gle.com>,
        <dave.hansen@...ux.intel.com>, <tiny.windzz@...il.com>,
        <jhubbard@...dia.com>, <david@...hat.com>
CC:     <linmiaohe@...wei.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

From: Miaohe Lin <linmiaohe@...wei.com>

The jump labels try_prev and none are not really needed
in find_mergeable_anon_vma(), eliminate them to improve
readability.

Reviewed-by: David Hildenbrand <david@...hat.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
-v2:
	Fix commit descriptions and further simplify the code
	as suggested by David Hildenbrand and John Hubbard.
-v3:
	Rewrite patch version info. Don't show this in commit log.
-v4:
	Get rid of var near completely as well.
---
 mm/mmap.c | 36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 91d5e097a4ed..4d93bda30eac 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1273,26 +1273,22 @@ static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_
  */
 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
 {
-	struct anon_vma *anon_vma;
-	struct vm_area_struct *near;
-
-	near = vma->vm_next;
-	if (!near)
-		goto try_prev;
-
-	anon_vma = reusable_anon_vma(near, vma, near);
-	if (anon_vma)
-		return anon_vma;
-try_prev:
-	near = vma->vm_prev;
-	if (!near)
-		goto none;
-
-	anon_vma = reusable_anon_vma(near, near, vma);
-	if (anon_vma)
-		return anon_vma;
-none:
+	struct anon_vma *anon_vma = NULL;
+
+	/* Try next first. */
+	if (vma->vm_next) {
+		anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
+		if (anon_vma)
+			return anon_vma;
+	}
+
+	/* Try prev next. */
+	if (vma->vm_prev)
+		anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
+
 	/*
+	 * We might reach here with anon_vma == NULL if we can't find
+	 * any reusable anon_vma.
 	 * There's no absolute need to look only at touching neighbours:
 	 * we could search further afield for "compatible" anon_vmas.
 	 * But it would probably just be a waste of time searching,
@@ -1300,7 +1296,7 @@ struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
 	 * We're trying to allow mprotect remerging later on,
 	 * not trying to minimize memory used for anon_vmas.
 	 */
-	return NULL;
+	return anon_vma;
 }
 
 /*
-- 
2.21.GIT