[PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region

From: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
To: mhocko@suse.com
Cc: oleg@redhat.com, akpm@linux-foundation.org, cmetcalf@ezchip.com,
	mszeredi@suse.cz, viro@zeniv.linux.org.uk, dave@stgolabs.net,
	kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com,
	aarcange@redhat.com, iamjoonsoo.kim@lge.com, jack@suse.cz,
	xiexiuqi@huawei.com, vbabka@suse.cz, Vineet.Gupta1@synopsys.com,
	riel@redhat.com, gang.chen.5i5j@gmail.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
Subject: [PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region
Date: Tue, 17 Nov 2015 18:26:38 +0100	[thread overview]
Message-ID: <1447781198-5496-1-git-send-email-kwapulinski.piotr@gmail.com> (raw)
In-Reply-To: <20151117161928.GA9611@redhat.com>

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@gmail.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

