linux-kernel - [PATCH] mm: mmap: Simplify the failure return working flow

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Message-ID: <BLU436-SMTP37E3EE1A24E7A3EEEDBFA7B9780@phx.gbl>
Date:	Wed, 19 Aug 2015 06:27:58 +0800
From:	Chen Gang <xili_gchen_5257@...mail.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	riel@...hat.com, Michal Hocko <mhocko@...e.cz>,
	sasha.levin@...cle.com
CC:	linux-mm@...ck.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm: mmap: Simplify the failure return working flow

__split_vma() doesn't need out_err label, neither need initializing err.

copy_vma() can return NULL directly when kmem_cache_alloc() fails.

Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
---
 mm/mmap.c | 39 +++++++++++++++++++--------------------
 1 file changed, 19 insertions(+), 20 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 8e0366e..35a4376 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2461,7 +2461,7 @@ static int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 	      unsigned long addr, int new_below)
 {
 	struct vm_area_struct *new;
-	int err = -ENOMEM;
+	int err;
 
 	if (is_vm_hugetlb_page(vma) && (addr &
 					~(huge_page_mask(hstate_vma(vma)))))
@@ -2469,7 +2469,7 @@ static int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 	if (!new)
-		goto out_err;
+		return -ENOMEM;
 
 	/* most fields are the same, copy all, and then fixup */
 	*new = *vma;
@@ -2517,7 +2517,6 @@ static int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 	mpol_put(vma_policy(new));
  out_free_vma:
 	kmem_cache_free(vm_area_cachep, new);
- out_err:
 	return err;
 }
 
@@ -2958,23 +2957,23 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
 		*need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
 	} else {
 		new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
-		if (new_vma) {
-			*new_vma = *vma;
-			new_vma->vm_start = addr;
-			new_vma->vm_end = addr + len;
-			new_vma->vm_pgoff = pgoff;
-			if (vma_dup_policy(vma, new_vma))
-				goto out_free_vma;
-			INIT_LIST_HEAD(&new_vma->anon_vma_chain);
-			if (anon_vma_clone(new_vma, vma))
-				goto out_free_mempol;
-			if (new_vma->vm_file)
-				get_file(new_vma->vm_file);
-			if (new_vma->vm_ops && new_vma->vm_ops->open)
-				new_vma->vm_ops->open(new_vma);
-			vma_link(mm, new_vma, prev, rb_link, rb_parent);
-			*need_rmap_locks = false;
-		}
+		if (!new_vma)
+			return NULL;
+		*new_vma = *vma;
+		new_vma->vm_start = addr;
+		new_vma->vm_end = addr + len;
+		new_vma->vm_pgoff = pgoff;
+		if (vma_dup_policy(vma, new_vma))
+			goto out_free_vma;
+		INIT_LIST_HEAD(&new_vma->anon_vma_chain);
+		if (anon_vma_clone(new_vma, vma))
+			goto out_free_mempol;
+		if (new_vma->vm_file)
+			get_file(new_vma->vm_file);
+		if (new_vma->vm_ops && new_vma->vm_ops->open)
+			new_vma->vm_ops->open(new_vma);
+		vma_link(mm, new_vma, prev, rb_link, rb_parent);
+		*need_rmap_locks = false;
 	}
 	return new_vma;
 
-- 
1.9.3
--
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