linux-kernel - [PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap

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Date:	Tue, 17 Nov 2015 18:26:38 +0100
From:	Piotr Kwapulinski <kwapulinski.piotr@...il.com>
To:	mhocko@...e.com
Cc:	oleg@...hat.com, akpm@...ux-foundation.org, cmetcalf@...hip.com,
	mszeredi@...e.cz, viro@...iv.linux.org.uk, dave@...olabs.net,
	kirill.shutemov@...ux.intel.com, n-horiguchi@...jp.nec.com,
	aarcange@...hat.com, iamjoonsoo.kim@....com, jack@...e.cz,
	xiexiuqi@...wei.com, vbabka@...e.cz, Vineet.Gupta1@...opsys.com,
	riel@...hat.com, gang.chen.5i5j@...il.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Piotr Kwapulinski <kwapulinski.piotr@...il.com>
Subject: [PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region

The following flag comparison in mmap_region is not fully correct:

if (!(vm_flags & MAP_FIXED))

The vm_flags should not be compared with MAP_FIXED (0x10). It is a bit
confusing. This condition is almost always true since VM_MAYREAD (0x10)
flag is almost always set by default. This patch removes this condition.

Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@...il.com>
---
 mm/mmap.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 2ce04a6..02422ea 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1547,13 +1547,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
 		unsigned long nr_pages;
 
-		/*
-		 * MAP_FIXED may remove pages of mappings that intersects with
-		 * requested mapping. Account for the pages it would unmap.
-		 */
-		if (!(vm_flags & MAP_FIXED))
-			return -ENOMEM;
-
 		nr_pages = count_vma_pages_range(mm, addr, addr + len);
 
 		if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
-- 
2.6.2

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